Poptronics-1975-01

.thereHOW TO "READ" FM TUNER SPECIFICATIONSbeI canPopular ElectronicsonlyWORLD'S LARGEST -SELLING ELECTRONICS MAGAZINE JANUARY 1975/75(Done best.PROJECT BREAKTHROUGH !World's First Minicomputer Kitto Rival Commercial Models...ALTAIR 8800 SAVE OVER ß1O00ALTAIR 8800n ..r IRIS a. ., .r._+,-MIX rre ,.r in r . r AS DI ,r rs )SIAMsN All u . All u AT ., Al At All w. ,s'v--kae wus...r _*ue ar nv uurr rnar rwreu su.ALSO IN THIS ISSUE:An Under -$90 Scientific Calculator ProjectCCD's -TV Camera Tube Successor?Thyristor - Controlled PhotollashersTEST REPORTS:Technics 200 Speaker SystemPioneer RT -1011 Open -Reel Record.--Tram Diamond -40 CB A ""'Xi31dk21IS HIPP Z011SNEdmund Scientific "Kir im a-1101Hewlett- Packard 5."- 01 40AV zaoatott )INr la1ZSQ0, vs saSASS-0.^t,..

The finest stereo receivers the worldhas ever known.Pioneerbelieves that any objectivecomparison of quality /performance/price between our new SX -1010,SX -939 and SX -838 AM -FM stereoreceivers and any other fine receiverswill overwhelmingly indicate Pioneer'soutstanding superiority and value.The most powerful everPioneer uses the most conservativepower rating standard: continuouspower output per channel, with bothchannels driven into 8 ohm loads,across the full audio spectrum from20Hz to 20,000 Hz. Despite thisconservatism, the SX -1010 farsurpasses any unit ever produced withan unprecedented 100 + 100 watts RMSat incredibly low 0.1 % distortion.Closely following are the SX -939(70 + 70 watts RMS) and the SX -838(50 + 50 watts RMS) both with lessthan 0.3% distortion. Dual powersupplies driving direct -coupledcircuitry maintain consistent highpower output with positive stability. Afail -safe circuit protects speakers andcircuitry against damage fromoverloading.Outstanding specificationsfor flawless receptionFM reception poses no challenge to theexceptionally advanced circuitry ofthese fine instruments. Their FM tunersections are designed with MOS FETs,ceramic filters and phase lock loopcircuitry. The result is remarkablesensitivity, selectivity and capture ratiothat brings in stations effortlessly,clearly and with maximum channelseparation.SX -1810 SX -939 SX -838FM Sensitivity (IHF) 1.7uV 1.8uV 1.8uV(the lower the better)Selectivity 90dB 80dB 80dB(the higher the better)Capture Ratio 1dB 1dB 1dB(the lower the better)Signal /Noise Ratio 72dB 70dB 70dB(the higher the better)n4s51.0W 0.17 MCT4JTE,t1,1_1-,,,a.,o_Z'kA.11e ryuAtawInt.10kHZTotal versatility plus innovationsOnly your listening interests limit thecapabilities of these extraordinaryreceivers. They have terminals forevery conceivable accommodation:records, tape, microphones, headsets- plus Dolby and 4- channelmultiplex connectors. Completelyunique on the SX -1010 and SX -939 istape -to -tape duplication whilelistening simultaneously to anotherprogram source. The SX -838innovates with its RecordingCv P1qtVCC.n 5TEt7fU RECEIVER MOOEI Sx 939(.) PIOMEU2 gTEREO RECEIVER MODEL Sx-1010. iTá1 ,wO-z u=*CMtpali'.'.

- . .....,....v...,.Iceivers the world'.w..ione,er believes that any objectivecomparison of quality /performance/price between our new SX -1010,'EX_2 9 and SX -838 AM -FM stereoreceivers and any other fine receiverswill overwhelmingly indicate Pioneer'soutstanding superiority and value.The most powerful everPioneer uses the most conservativepower rating standard: continuouspower output per channel, with bothchan:lels driven into 8 ohm loads,across the full audio spectrum from20Hz to 20,000 Hz. Despite thisconservatism, the SX -1010 farsurpasses any unit ever produced withan unprecedented 100 + 100 watts RMSat incredibly low 0.1 % distortion.Closely following are the SX -939(70 + 70 watts RMS) and the SX -838(50 + 50 watts RMS) both with lessthan 0.3% distortion. Dual powersupplies driving direct -coupledcircuitry maintain consistent highpower output with positive stability. Afail -safe circuit protects speakers andcircuitry against damage fromoverloading.Outstanding specificationsfor flawless receptionFM reception poses no challenge to theexceptionally advanced circuitry ofthese fine instruments. Their FM tunersections are designed with MOS FETs,ceramic filters and phase lock loopcircuitry. The result is remarkablesensitivity, selectivity and capture ratiothat brings in stations effortlessly,clearly and with maximum channelseparation.SX -1010 SX -939 SX -838FM Sensitivity (IHF) 1.7uV 1.8uV 1.8uV(the lower the better)Selectivity90dB 80dB 80dB(the higher the better)Capture Ratio 1dB 1dB 1dB(the lower the better)Signal /Noise Ratio(the higher the better)72dB 70dB 70dBTotal versatility plus innovationsOnly your listening interests limit thecapabilities of these extraordinaryreceivers. They have terminals forevery conceivable accommodation:records, tape, microphones, headsets- plus Dolby and 4- channelmultiplex connectors. Completelyunique on the SX -1010 and SX -939 istape -to -tape duplication whilelistening simultaneously to anotherprogram source. The SX -838innovates with its Recording-.A.. -10010aIS O .e-3,025 possible tonal compensations with unique twin stepped tone controls(SX -1010, SX -939)Selector that permits FM recordingwhile listening to records and viceversa. Up to three pairs of speakersmay be connected to each model.INPUTS SX -1010 SX -939 SX -838Tape monitor /4-ch. 3 2 2adaptorPhonoMicrophone222221Auxiliary1 11Noise reduction1 11OUTPUTSSpeakersTape Rec. /4 -ch.adaptorHeadsetsNoise reduction4- channel MPXSX-5353 3 33 2 2Master control system capabilityPioneer's engineers have surpassedthemselves with a combination ofcontrol features never before foundin a single receiver. All three unitsinclude: pushbutton function selectionwith illuminated readouts on theultra wide tuning dial, FM and audiomuting, loudness contour, hi /lowfilters, dual tuning meters and adial dimmer.Never before used on a receiverare the twin stepped bass and trebletone controls found on the SX -1010and SX -939. They offer over 3,000tonal variations. A tone defeatswitch provides flat responseinstantly throughout the audiospectrum. The SX -838 featuresSX-836Pr*switched turnover bass and treblecontrols for more precise tonalcompensation for room acoustics andother program source characteristics.In their respective price ranges,these are unquestionably the finestvalues in stereo receivers the worldhas ever known. Audition theiruniqueness at your Pioneer dealer.SX -1010 - $699.95; SX -939 - $599.95,SX -838 - $499.95. Prices includewalnut cabinets.Also new and moremoderately priced.Pioneer's most complete and finestline of receivers ever, presentsequally outstanding values starting at$239.95. Shown here are the SX -535- $299.95, SX -636 - $349.95, SX -737- $399.95. All with walnut cabinets.U.S. Pioneer Electronics Corp.,75 Oxford Drive, Moonachie,New Jersey 07074West: 13300 S. Estrella, Los Angeles90248 /Midwest: 1500 Greenleaf,Elk Grove Village, Ill. 60007 /Canada:S.H. Parker Co.\t(\\ -1Pwhen you want something betterus,.a..,...hIONt.C-t7 tiirREO RrGFbER MOOí: '` -"; ri,100 102 101 13690 VI It 130 AO ßU tlt}91''j'r''r)--,....,,.r. ',r96,,, 90E0 ¡f0108inii,i..... .i............qMHzSP-ASP-ElAM RM PHdN0-1 PFO,p$ AUX,11...L1A.,,.TqR'3r,=..,on.ti.',:.NCfVOLUME1 0. .r.. MAX

Earnan extra$2000per yearFind out how you can earn anextra $2000 or more per year restoringonly a few color and blackand white tubes per week. Fullcolor brochure shows you howto make more money and satisfymore customers on almostevery call. Write today!JANUARY 1975 VOLUME 7, NUMBER 1Popular Electronics°WORLD'S LARGEST- SELLING ELECTRONICS MAGAZINEFEATURE ARTICLESTHYRISTOR CIRCUITRY FOR ELECTRONIC PHOTOFLASHERS Michele Frank 39An SCR trigger provides faster recycling, more flashes and quick recharge.SOLID -STATE IMAGE SENSORS -TV CAMERA TUBE SUCCESSOR? Harry Garland & Roger Melen 43KEYING AND VCA CIRCUITS FOR ELECTRONIC MUSIC INSTRUMENTS, PART I Don Lancaster 60HOW TO "READ" FM TUNER SPECS Julian D. Hirsch 68LIGHTNING DAMAGE INSURANCE JOBS John T. Frye 72How lightning damage occurs and how to prevent it.CONSTRUCTION ARTICLESALTAIR 8800 MINICOMPUTER, PART I H. Edward Roberts & William Yates 33The most powerful minicomputer project ever presented -for under $400.AN IGNITION TIMING LIGHT FOR IMPROVING GAS ECONOMY Anthony Caristi 50BUILD AN UNDER -990 SCIENTIFIC CALCULATOR Martin Meyer 53Ten -digit, full -function, pocket -size.IC SPEED CONTROLLER FOR HO MODEL RAILROADS Robert D. Pascoe 58BUILD THE TRANSISTOR IDENTOMETER John T. Bailey 69Identifies leads and polarities and shows up bad devices.SIMPLE SQUELCHING CIRCUIT FOR STEREO FM TUNERS Lawrence N. Dworsky 71New467 CRTRestorer /Analyzer$279*With the profit restorer:Profit in the home. After replacing a componentyou've often noticed a less than perfect picture. It'salmost always due to a weak picture tube. The fewminutes you spend with the 467 Restorer will giveyour customer brilliance and sharpness that will makeher pleased to pay for the improved picture.Profit in the shop. "Sixty -five dollars and the picturestill doesn't look as good as it used to!" How manytimes have your customers said that to you? You neednot hear it again! Use the 467 Restorer on every majorjob and your customer will thank you for returning hisset working like new.Most -Powerful Rejuvenation, but most gentle too.There's only one CRT Restorer that restores the pictureto like new and analyzes tube condition so accuratelythat you can safely guarantee restoration forup to five years. You get extra safety from our automaticrestoration method that prevents cathodestripping.2TriDynamic true test. The B & K TriDynamic methodtests all three guns simultaneously. It measures truebeam current that passes through G1 aperture, unlikeother testers that measure meaningless cathode to G1current. Leakage indication even includes cathode -to- cathode and there's an exclusive B & K focus continuitytest.Simplest operation. Exclusive integrated circuitrylets you test all picture tubes with the same, defined -on- the -front -panel procedure ... including "in- line ",Trinitron and tubes with common G1 and G2. See yourdistributor or write Dynascan.CIRCLE NO. 7 ON READER SERVICE CARD'Six sockets included;optional sockets also shown.PRODUCTS OFDYIVASCAILI1801 W. Belle Plaine Ave.Chicago, IL 60613 (312) 327 -7270POPULAR ELECTRONICSJANUARY 1975COLUMNSSTEREO SCENE Ralph Hodges 22Mikes and miking.SOLID STATE Lou Garner 88Predictions for 1975.CB SCENE Len Buckwalter 92CB's Red Baron.AMATEUR RADIO Herbert S. Brier 94Reception and the atmosphere.TEST EQUIPMENT SCENE Leslie Solomon 98Rejuvenating elderly equipment.HOBBY SCENE Editorial Staff 102PRODUCT TEST REPORTSTECHNICS BY PANASONIC MODEL T -200 SPEAKER SYSTEMPIONEER MODEL RT -1011L STEREO TAPE RECORDERHEWLETT -PACKARD MODEL 5381A FREQUENCY COUNTERTRAM DIAMOND 40 AM CB TRANSCEIVEREDMUND SCIENTIFIC KIRLIAN ELECTROPHOTOGRAPHY KITDEPARTMENTSEDITORIALThe Home Computer Is Here!LETTERSNEW PRODUCTSNEW LITERATURENEWS HIGHLIGHTSELECTRONICS LIBRARYPOPULAR ELECTRONICS, January 1975, Volume 7, Number 1. Publishedmonthly at One Park Avenue, New York, NY 10016. One year subscriptionrate for U.S., Possessions and Canada, $6.98; all other countries,$8.98. Second class Postage paid at New York, NY and at additionalmailing offices. Authorized as second class mail by the Post Office Departm ent, Ottawa, Canada an d for payment of postage in cash. Subscriptionservice and Forms 3579; P.O. Box 2774, Boulder, CO 80302.POPULAR ELECTRONICS Including ELECTRONICS WORLD, TradeMark Registered. Indexed in the Reader's Guide to Periodical Literature.COPYRIGHT 01974 BY ZIFF -DAVIS PUBLISHING COMPANY. ALLRIGHTS RESERVED.Art Salsberg787980818246121626100Ziff -Davis also publishes Boating, Car and Driver, Cycle, Flying, ModernBride, Popular Photography, Skiing and Stereo Review.Forms 3579 and all subscription correspondence should be addressedto POPULAR ELECTRONICS, Circulation Dept., P. 0. Box 2774, Boulder,CO 80302. Please allow at least eight weeks for change of address. Includeyour old address, as well as new -enclosing, if possible, an addresslabel from a recent issue.Editorial contributions must be accompanied by return postage andwill be handled with reasonable care; however publisher assumes noresponsibility for return or safety of art work, photographs, models, ormanuscripts.3

Popular ElectronicsEDGAR W. HOPPERPublisherARTHUR P. SALSBERGEditorial DirectorLESLIE SOLOMONTechnical EditorJOHN R. RIGGS.Managing EditorEDWARD I.BUXBAUMArt DirectorALEXANDER W. BURAWAAssociate EditorJOHN McVEIGHAssistant EditorANDRE DUZANTTechnical IllustratorHERBERT S. BRIERLEN BUCKWALTERLOU GARNERGLENN HAUSERJULIAN D. HIRSCHRALPH HODGESWALTER G. JUNGART MARGOLISContributing EditorsJOSEPH E. HALLORANAdvertising DirectorJOHN J. CORTONAdvertising SalesLINDA BLUMAdvertising Service ManagerPEGI McENEANEYExecutive AssistantSTANLEY NEUFELDAssociate PublisherFURMAN H. HEBBGroup VP, Electronics & PhotoZIFF -DAVIS PUBLISHING COMPANYPopular ElectronicsEditorial and Executive OfficesOne Park Avenue New York, New York 10016212- 725 -3500Hershel B. Sarbin, PresidentFurman Hebb, Executive Vice President and TreasurerPhillip T. Heffernan, Senior Vice President, MarketingEdward D. Muhlfeld, Senior Vice President, SportsDivisionPhilip Sine, Senior Vice PresidentFrank Pomerantz, Vice President, Creative ServicesArthur W. Butzow, Vice President, ProductionLawrence Sporn, Vice President, CirculationGeorge Morrissey, Vice PresidentSydney H. Rogers, Vice PresidentSidney Holtz, Vice PresidentCharles B. Seton, SecretaryEdgar W. Hopper, Vice President, Electronics Div.William Ziff, ChairmanW. Bradford Briggs, Vice ChairmanMidwestern OfficeThe Pattis Group, 4761 West Touhy Ave.,Lincolnwood, Illinois 60644, 312 679-1100GERALD E. WOLFE, GEORGE B. MANNIONDAVID ALLENWestern Office9025 Wilshire Boulevard, Beverly Hills, CA 90211213 273 -8050; BRadshaw 2 -1161Western Advertising Manager, BUD DEANJapan: James YogiOji Palace Aoyama; 6 -25, Minami Aoyama6 Chome, Minato -Ku, Tokyo 407 -1930/6821,582 -2851. MemberAudit Bureauof CirculationsklAThe publisher has no knowledge of any proprietaryrights which will be violated by the making or using of anyitems disclosed in this issue.4THE HOME COMPUTER IS HERE!EditorialFor many years, we've been reading and hearing about howcomputers will one day be a household item. Therefore, we'reespecially proud to present in this issue the first commercial typeof minicomputer project ever published that's priced within reachof many households -the Altair 8800, with an under -$400complete kit cost, including cabinet.To give you some insight to our editorial goal for this momentousproject, we were determined not to present a digital computerdemonstrator with blinking LED's that would simply be fun to buildand watch, but suffer from limited usefulness. High chip costswould have made this a most expensive toy. What we wanted forour readers was a state -of- the -art minicomputer whosecapabilities would match those of currently available units at amere fraction of the cost.After turning down three computer project proposals that didnot meet these requirements, the breakthrough was made possiblewith the availability of the Intel 8080 n- channel CPU (centralprocessor unit) -the highest -performance, single -chip processoravailable at this time. As a result, Altair 8800 offers up to 65,000words of memory, 256 inputs and outputs simultaneously, bussline expansion, subroutines that are enormously deep, and fastcycle time, among other desirable characteristics. Peripheralequipment such as a "smart" CRT terminal is expected to beavailable, too, to make up a within -pocket- book -reachsophisticated minicomputer system.Unlike a calculator -and we're presenting an under -$90scientific calculator in this issue, too -computers can makelogical decisions for an accounting system, navigation computer,time -shared computer, sophisticated intrusion system, andthousands of other applications. The "power" ofAltair8800 is suchthat it can handle many programs simultaneously.What we're presenting to you, the POPULAR ELECTRONICS reader,therefore, is a minicomputer that will grow with your needs, ratherthan one that will be obsoleted as you move more deeply intocomputerized applications. With minicomputers exhibiting anannual growth rate of some 50 %, according to the E.I.A., and withpredictions that six out of ten computers sold by 1975 will bemini's, you can be sure that there will be manifold uses we cannoteven think of at this time.There'll be more coverage on the subject in future issues.Meanwhile, the home computer age is here -finally.POPULAR ELECTRONICSRadio Shack deals...from the top of its decks!The top of our Realistie line. An Auto -Reverse Dolby deckfor 2 -hour stereo recordings without flipping the cassetteFREE New 1975Radio Shack CatalogOVER 2000 PRODUCTSEXCLUSIVES ON EVERY PAGEBEAUTIFUL FULL COLORStereo Quadraphonic PhonographsTV Antennas Radios Citizens BandKits Recorders Tape ToolsAuto Tune -Up Electronic PartsTest Instruments More!164 pages of the finest inhome and hobby electronics.Respected brand names likeRealistic, Micronta, Archer,Science Fair - and they'reavailable only at RadioShack stores and dealersnationwide! See what's reallynew in electronics by gettingthis catalog now.SEND FOR YOURS TODAY!FILL OUT COUPON BELOW1975 Mail to Radio Shack, P. O. Box 1052,Catalog Ft. Worth, Texas 76101. (Please print.)NameStreetCityStateL _JANUARY 1975ZIPApt. No4671The Realistic SCT -7 with Auto -Reverse. What convenience!You can record or play an entire concert, on both sides of thetape, for two uninterrupted hours. Or record or play on justone side with Auto -Stop. Or play an entire cassette over andover without stopping. The SCT -7 does it all- automatically.And what features and sound! Dolby* noise reduction system.Bias switch for Cr02 or standard tape. Record edit button toinsert silence between selections. Headphone jack. Big,illuminated VU meters. And lighted indicators for record, tapetravel direction and Dolby. U.L. listed. What a deal! #14 -897.*Dolby is a trademark of Dolby Laboratories, Inc.... and an 8 -track deck that's loaded!The Realistic TR -801 with Digital Timer. It couldn't be easierto use. The unique timer shows the minutes and seconds recordedon each cartridge -you always know exactly how muchtime remains. And pushbuttons control everything. Auto -Stopand eject at the end of each program or just program -4. Repeatand continuous play. Pause and fast forward. Manual power -eject. It makes you a recording pro. U.L. listed. #14 -925.There's only one place you can find them . . .Master Charge orBank Americard atftaduo IhaeKA TANDY CORPORATION COMPANYOVER 3000 STORES 50 STATES 7 COUNTRIES_J participating stores Retail prices may vary at individual stores and dealers.CIRCLE NO. 31 ON READER SERVICE CARD5

II_The Ultimate in Ignition Systems!* ELIMINATES BREAKER POINTS.Perlect Timing and Dwell never change!* Eliminates Tune -ups.Never wears out or needs any Maintenance._ * The Most Advanced"fl "OPTO- ELECTRIC SYSTEM"The Allison Breakerless System eliminates the Pointsand Condenser, replacing them with an Opto- ElectronicTrigger, using a Light- Emitting Diode and Phototransistor.Also completely eliminates wiper -arm "friction" wear.The only "TRUE" Electronic Ignition ... that you can installfor under $100. Gives 40 -times more Timing Accuracythan ANY system using mechanical Breaker- Points!Unlimited RPM. Smoother running .(No timing fluctuationas with Magnetic units). Unaffected by Temperature,Moisture, or Vibration! All Solid -State Components.Easier Starting under any condition! Increased Horsepower.Sparkplugs last longer. Perfect timing increases engineEfficiency and Gas Mileage up to 30%!Quick and Easy Installation!* Tested and Proven reliability.Only $4995Complete.SATISFACTION GUARANTEED!1 -YEAR FACTORY WARRANTY.(State Make, Year, Engine Size). (Calif. Res. add Tax).CONVERT YOUR "C-O" UNIT TO BREAKERLESS!"TRIGGER- UNIT" ONLY $34.95* Send Postcard for FREE BROCHURE Today.ALLISON AUTOMOTIVE CO.`P.O. Box 881 -P, TEMPLE CITY, CAL. 91788CIRCLE NO. 2 ON READER SERVICE CARDCOMING UP INTHE FEBRUARYPopular ElectronicsBuild the First, Low -CostAll -Solid -State N CameraA VU Meter withNo Moving PartsHow Phase- LockedLoops WorkTest Reports:Marantz 4270 Stereo ReceiverGarrard Zero 100 $B TurntableOrtofon VMS -20E Phono CartridgeLafayette Corn-Phone 23 CBTransceiverData Technology Models20 & 21 DMM's.6LettersRUMOR IS NO SECRETwas surprised to discover, in your Octoberissue, that Radio Canada Internationalis engaged in "clandestine" broadcastingto Russia from Sines in Portugal,over a station which (as stated on page 56)is "reported to be secretly owned by theWest German government."There was no need for the author to haverecourse to rumors about the Sines transmitter,for what he advances as a conspiratorialsecret is published in a moreaccurate version ... in the current WorldRadio Handbook, page 92, with cross referencesas to users.AN IC BY ANOTHER NUMBERALAN BROWNRadio Canada InternationalMontreal, Can.The Exar integrated circuit used in my"Private Messages With a Voice Scrambler"project (September 1974) has a newpart number. It is now called theXR2208CP. Please advise your readers ofthis change.SETTING THE RECORD STRAIGHTJOSEPH B. WICKLUND, JR.Northwest EngineeringBothell, Wash.Mr. Lancaster's series of articles on electronicmusic synthesizers has served a usefulservice to your readers. However,"Selecting an Electronic Music Synthesizer"(October 1974) contains a few inaccuracies:1. The ElectroComp 101 is manufacturedby Electronic Music Laboratories (EML),which has no connection with EMSA;2. The Synthi 100 is manufactured byEMS (London) Ltd., who also manufacturelive- performance EM systems that Mr.Lancaster failed to mention. (The Synthi100 sells for $30,000 -not $20,000);3. Electronic Music Studios of America,Inc., (EMSA) is not a manufacturer but theAmerican distributor for EMS (London)Ltd's products;4. EMSA and ARP do not have the samezip code; EMSA's is 01002.JANICE B. ANDRESManaging DirectorEMSA Inc.Amherst, Mass.PE ON THE AIRJust a note of appreciation for the newlarger format. You have made a greatmagazine a lot more enjoyable. Over theyears, I have used or adopted a number ofideas presented in POPULAR ELECTRONICShere at radio station KORI (FM), a trick thatoften saved a great deal of time -let alonethe money involved when equated againstthe cost of commercial equivalents.TOM WIRCHChief EngineerKSLM /KORI (FM)Salem, Ore.THE PARTS PROCUREMENT DILEMMAwould like to build the "Nine-ChannelStereo Equalizer" (May 1974) but I am havingdifficulty finding a dealer who handlesthe 5558 op -amp IC's required. Anotherproblem is that no pin numbers are shownfor the IC in the schematic.JOHN E. RICEGeorgetown, Ontario, CanadaYou can obtain these IC's from SouthwestTechnical Products Corp. (see theParts List in the article for the address). Asfor pin numbering, the omission was intentional.The 5558 is available in severalpackage configurations, all with differentlead identification.In "Supressing Transients in Solid -StateEquipment" (July 1974), it was stated thatthe General Electric 6RS20 -SP4B4 thyrectorshould be available at local electronicsstores. Well, I've tried six different storeswithin a 20 -mile radius of my home andhaven't been able to locate one that handlesthis device. Can you help me with amail -order address?KENNETH L. METCALFWoodstown, N.J.The 6RS20 -SP4B4 thyrector is availablefrom Newark Electronics, 500 N. PulaskiRd., Chicago, IL 60624. However, there is$25 minimim for mail orders. The GE distributornearest you is at 200 Main Avenue,Clifton, NJ 07014.THE AMATEUR RADIO SCENECongratulations on the return of your"Amateur Radio" column. I was verypleased to see it in the October 1974 issue. Ican hardly wait for the next column to appear.My only criticism is that the column isa quarterly; it should be a monthly.Edward LeBlanc, VE1AMNPrince Edward Island, CanadaIn the October 1974 "Amateur Radio"column there appear to be two discrepanciesin callsigns. The San Franciscostation's callsign should be K101, notK -101, while I believe the correct callsignfor King Hussein is JY1 -nor WJ1.Fred BeckerNorth Attleboro, Mass.POPULAR ELECTRONICSThe "NEW LOOK"1975LAFAYETTERADIO ELECTRONICSlectronics catalog no. 750CATALOG1975 eNEW! Bigger PagesNEW! More Full ColorUTEpDISTRIBUTEDIONW.ONLY_ NAT WITH A MAJOIT'S CATALOGFULL-LINESHOWING OF THE rSpNAME-BRANDELECTRONICS 19751FORIINEW! Easier -to -Read TypefreeMAIL TODAY!JANUARY 1975SEND'TODAY!Lafayette Radio Electronics111 Jericho Tpke., Syosset, L.I., N.Y. 11791NameStreetCityStateIf you're interested in electronics you NEEDthis catalog! Completely re- designed for easier -than -ever ordering, with the newest and bestLafayette and national -brand products for '75.And you get the same quality and servicethat has made Lafayette a leader for 55years. Iron -clad guarantees! Lowest Prices!Professional Service! State -of- the -art Equipment!Pick and choose from over 18,000quality electronics products! Now, morethan ever, we're your "Single- trip" shoppingcenter for everything in electronics.STORES COAST TO COASTSend me your FREE 1975 Catalog.ZipAptSAVE ON EXCLUSIVELAFAYETTE PRODUCTSPLUS THE BEST MAJORBRAND NAMESStereo and 4- Channel Music SystemsTape Recording Equipment CarStereo and Accessories CB and HamGear Police /Public Service ReceiversCar Stereo and AccessoriesAntennas Cameras TV PA andTest Equipment Music Instrumentsand Amplifiers Books ElectronicCalculators Security SystemsPLUS PARTS, TUBES, BATTERIES,HARDWARE - ALL YOU NEEDFOR QUALITY LIVING THROUGHELECTRONICSLafayetteListen to us, you can't go wrong.NameStreetCityStateCheck Your Yellow Pages or Shop by Mall35015Send a 1975 Electronics Catalogto my friend.1111111111111111111111111111/CIRCLE NO. 21 ON READER SERVICE CARD7ZipApt

The real way to learn digital electronics!NRI is the onlyschool to trainyou at home onareal digitalcomputer.Only NRI offers you fiveTV /Audio Servicing CoursesNRI's complete communicationcourse includes your ownCB Training TransceiverLearn computer design, construction, maintenanceand programming techniques on yourown digital computer using a professionaldigital multimeter !Qualified technicians are urgently neededfor careers in the exciting new field of digitaland computer electronics . . . and the bestway to learn digital logic and operations isnow available to you in NRI's Complete ComputerElectronics Course.This exclusive course trains you at homeon your own digital computer ! This is no beginner's"logic trainer ", but a complete programmabledigital computer that contains amemory and is fully automatic. You build ityourself and use it to define and flow -chart aprogram, code your program, store your programand data in the memory bank. Press thestart button and the computer solves your8NOW...YOUR OWN DIGITAL (31/2 DIGITS)MULTIMETER INCLUDEDAT NO EXTRA COST!The latest in digital testing equipment . . .along with valuable training experiments indigital techniques.problem and displays the result instantly.The NRI digital computer is one of 10 kitsyou receive in the NRI Complete ComputerElectronics Course. You build and use yourown 31/2 digit digital multimeter ... while youperform hundreds of experiments, buildinghundreds of circuits, learning organization,operation, troubleshooting and programming.POPULAR ELECTRONICSoColor TV repair is anotherbig opportunityfield right now andNRI can train you athome to service and repairany color or black& white TV, hi -fi equipment,AM -FM radios,and sound systems.You can choose fromourses, starting with a basic servicing courseth 65 lessons ... up to a Master Color TV course,mplete with 25" diagonal solid state color TV inndsome woodgrain cabinet. No other school offersmany choices or so much value.All courses are available with low down paymentd convenient monthly payments to fit your bud -t. And all courses provide professional tools andquipment along with NRI -designed kits for hands -n training. With the Master Course, for instance,ou receive your own 5" wide -band triggered sweepolid state oscilloscope, TV pattern generator, 31/2igit digital multimeter and a NRI 25" diagonalolid state television receiver expressly designed forcolor TV training.YOU PAY LESS WITH NRI TRAININGAND YOU GET MORE FOR YOUR MONEY.NRI employs no salesmen, pays no commissions. Wepass the savings on to you in reduced tuitions andx :tras in the way of professional equipment, testingastruments, etc. You can pay more, but you can'tret better training.,WARY 1975NRI prepares you for acareer in the rapidlyexpanding field of communications... a fielddestined to double inthe next decade ! NRIcan train you at homefor one of the thousandsof service andmaintenance jobs opening in AM and FM Transmissionand Reception, TV Broadcasting, MicrowaveSystems, Teletype, Radar, Marine Electronics,Mobile Communications and Aircraft Electronics.You train on your own 23- channel Johnson Transceiverand AC power supply ; a digital multimeter,for digital experiments and precise testing ; bite -size lessons leading to your FCC license and thecommunications field of your choice.NEARLY ONE MILLION STUDENTS IN60 YEARS HAVE LEARNED AT HOMETHE NRI WAY.Mail the insert card and discover for yourself whyNRI is the recognized leader in home study training.No salesman will call. Do it today and get started onthat new career.APPROVED UNDER GI BILLFor the career minded, we are approved for veteransbenefits. Check box on card for details.MAIL THE INSERT CARD FORYOUR FREE NRI CATALOGNo salesman will callNRI NRI SCHOOLSW414 r McGraw -Hill Continuing Education Center3939 Wisconsin Avenue,Ai' i Washington, D.C. 2001611

New ProductsAdditional information on new productscovered in this section is available fromthe manufacturers. Either circle the item'scode number on the Reader Service Cardinside the back cover or write to the manufacturerat the address given.HUNNICUT DIGITAL LOGIC PROBEThe model LCA -2 Logic Circuit Analyzer,made by Hunnicut Digital Electronics, displaysnot only the logic state of a test pointbut also the quality of the logic condition.Four lamps indicate voltage /logic levels:Good "0," Bad "0," Bad "1," and Good"1." The LCA -2 is compatible with DTL andTTL. Voltages up to 200 V ac or dc, claimsthe manufacturer, can be applied to theinput. The LCA -2 is supplied with a 4 -footcoaxial cable, BNC connector, and threeinput adapters. It can indicate polarity /dutycycle of pulse trains as high as 25 MHz. Theprobe measures 51/2-in. long and 5 /8 -in. indiameter. $69.50.CIRCLE NO. 70 ON READER SERVICE CARDPORTABLE FREQUENCY COUNTERThe C -65A Frequency Counter by GreatAmerican Miniatures is a completely portableunit with a frequency range of 10 Hz to65 MHz (1 Hz to 65 MHz optional). Thecounter uses TTL circuitry and a 6 -digitLED readout. An internal nickel- cadmiumpower source delivers 5 volts @ 2.2 Ah. A2.5 -MHz crystal oscillator is used as a timebase, and the unit can be used as asecondary frequency standard when calibratedagainst WWV. Sensitivity is 500 mV,and short -term stability is 1 part in 106/24hours. Dimensions of the C -65A, costing$269, are 6" x 3.5" x 2.9 ". Weight is 27ounces. Optional accessories include a300 -MHz prescaler, ac power supply, batterycharger, coaxial probe, and a carryingcase for any or all of the above.CIRCLE NO. 71 ON READER SERVICE CARD12"ISO -TIP" SOLDERING ACCESSORIESThe Wahl Clipper Corporation has introduceda line of accessories for its "Iso -Tipcordless soldering iron. The Soldering IronKit (Cat. #7600) includes the iron itself(only8" long and 6 ounces in weight) with a"safety lock" feature to prevent accidentaltip heating, a wall mounting bracket, a batteryrecharging unit, a #7535 general -purpose tip and instruction booklet. Optionalaccessories include #7545 fine tip,#7546 heavy -duty tip, #7595 protectivecarrier and the #7585 auto charger plugassembly that fits into a car cigarettelighter for recharging in transit.CIRCLE NO. 72 ON READER SERVICE CARDALTEC "STONEHENGE I" LOUDSPEAKERThe Altec Corp. has introduced theStonehenge I medium -efficiency loudspeakersystem designed for use with amplifierswith a minimum 25 -watt rms powercapacity. The floor- standing Stonehenge Ifeatures a columnar bass -reflex enclosure,a 12" high -compliance woofer with a9 -pound magnet structure, a front -mounted dividing network withcontinuously -variable, high- frequency attenuationcontrol, and a newly- designeddirect -radiator tweeter. Stonehenge I ishandcrafted of African Afromosian Teakveneers and complemented with a rawcocoa fabric snap -on grille, and is finishedon all four sides. The system at $329, requires1.4 square feet of floor space, and16" x 371/2" x 141/2 ". Weight is 75 lbs.CIRCLE NO. 73 ON READER SERVICE CARDCLARION AM /FM MPX /8 -TRACK CAR PLAYERClarion's new Model 608 8 -track car stereosystem incorporates an AM /FM multiplexradio. Among the Model 608's features areintegrated circuits, vertical -head trackingto minimize cross -talk, stereo indicatorlight, stereo /mono switch, 4 -watts rms perchannel output, and a removable faceplatefor in -dash installation. According to thecompany, the tape player has a frequencyresponse of 50 to 10,000 Hz, S/N of 45 dBmin. and wow and flutter below 0.3% .CIRCLE NO. 74 ON READER SERVICE CARDWHITE'S LIGHTWEIGHT METAL DETECTORWhite's Electronics announces its newlightweight, solid -state metal detector, theCoinmaster IV -4B Series II. This refinedversion of its earlier models boasts addedsensitivity, which is governed by a variablecontrol, a greater tuning range (both ofwhich aid searches over highly mineralizedareas), and longer battery life. A meter isincluded for visual as well as audible indication.Address: White's Electronics, 1012Pleasant Valley Road, Sweet Home,Oregon 97386.CIRCLE NO. 75 ON READER SERVICE CARDPIONEER FRONT -LOADING CASSETTE DECKPioneer Electronics' Dolbyized CassetteDeck, Model CT- F7171, features front -panel access for tape loading and allnecessary controls. This allows the unit tobe stacked above or below other components.Its transport system is powered by adc servo motor, for high starting torqueand immunity to voltage fluctuations.Other features include separate bias andequalization for ferric oxide and CrO2tapes,Dolby noise reduction, ferrite tape head,LED peak -level indicators, memory rewind,switchable level limiter and built -inmonitoring amplifier and headphone jack.Frequency response: 40 to 13,000 Hz ± 3dB (Cr02 tape); wow and flutter: less than0.1% (WRMS); S /N: 58 dB (Doblyized).CIRCLE NO. 76 ON READER SERVICE CARDKOSS PHASE 2 STEREOPHONESThe new Koss "Phase 2" stereo headphonesallow the listener to control theambience of the program he is listening to.According to the manufacturer, the listenercan either "move himself into the center ofthe orchestra" or "expand the musicalsphere around himself." In either "location"he can accentuate selected portionsof the orchestra, as if he moved towardsome of the artists. The Koss Phase 2 employsPanoramic Source controls, whichare thumbwheels at the lower edge of eachearcup, and a two -position Ambience Expander.It can also be used in the conventionalstereo mode. The medium -brownearphones are equipped with a 10 -ft coiledcord and. price is $75.CIRCLE NO. 77 ON READER SERVICE CARDJOHNSON MINI -SCANtm POCKET MONITORThe new Johnson "Mini- Scan" vhf scanningmonitor weighs only 9 ounces, (255g),while measuring 5.9 "x2.6 "x1.4 ". CMOSscanning circuitry and a newly designedlow -drain audio section provide extendedbattery life. The unit has a four -channelcapacity and a built -in ferrite bar antenna.Dual conversion and ceramic filters enhancesensitivity, adjacent -channel 'rejection,and good overall selectivity. TheMini -Scan is used on the 146 -174 -MHzband. Other features are a squelch control,POPULAR ELECTRONICSbuilt -in speaker, jacks for earphone or externalspeaker, and optional flexible antenna.The unit uses four AA cells and costs$119.95.CIRCLE NO. 78 ON READER SERVICE CARDHEATH HOME WEATHER STATIONA professional -type weather station, in kitform, is available from the Heath Company.The ID -1290 Weather Station features asolid -state thermometer that displayseither indoor or outdoor temperature at theflick of a switch, a solid -state anemometerwith switchable ranges for 0 -30 and 0 -90mph, and an electronic wind- directionindicator with individual glowing indicatorsto give 16 -point resolution around thecompass. Sensing devices are mounted ona single horizontal mast that may be attachedto a TV mast. All connecting wiresare contained in one cable. The ID1290,housed in a simulated walnut panel, maybe mounted vertically or horizontally and is$89.95, less cable.CIRCLE NO. 5 ON READER SERVICE CARDthe price formoving up to asweep /functiongeneratorjust came downto $149.50JANUARY 1975TURNER "ULTRA- KICKER" CB ANTENNAThe Turner Division of the Conrac Corp.,long a leading manufacturer of microphonesfor two -way radios, has introduceda line of "Signal Kicker" antennas. The"Ultra Kicker" model shows an interestingcombination of beam and omnidirectionalconfigurations. It has five elements. Acenter folded dipole receives power fromthe transmission line, and is surrounded byfour outer vertical dipoles, which areloaded through electronically switchedstubs. The antenna can be switched to provide8 different radiation patterns in45- degree steps, but it remains fixed andno rotator is needed. Gain is 6.2 dB over ahalf -wave dipole. VSWR is 1.5:1, and thefront -to -side ratio is 20 dB or better. Crossoveris 0.6 dB. Two other models, an omnidirectionalunit and a rotatable beam, areavailable at $79.95 and $119.95 respectively.Price of the "Ultra Kicker" is $239.95.CIRCLE NO. 80 ON READER SERVICE CARDB & K 3" TRIGGERED SWEEP SCOPEDynascan's new B&K oscilloscope, Model1431, has a bandwidth from dc to 10 MHz,and a sensitivity of 10 mV per division. Inaddition to the triggered sweep, sync isfully automatic. A three -step vertical attenuatoris included, and sweep time is variablefrom 0.5 is to 0.5 s per division, in 19calibrated regions, and 5X magnification isExact now offers a laboratory -qualitysweep /function generator at a price you'dpay for less- useful sine -square oscillators.And you'll get so much more out of thenew Model 195 than traditional audio testequipment, such as sine, square, triangleand swept waveforms ... even pulses.This new 2 Hz to 200 kHz instrument isthe practical answer to many of yoursignal source needs, whether you'rechecking audio equipment, testing breadboardedcircuits or teaching at the highschool or college level.An internal sweep generator lets yousweep, either linearly or logarithmically,the entire audio range of amplifiers orspeakers without changing ranges or eventouching a knob. The Model 195 has three1000:1 sweep ranges for frequencysweeping plus high and low level sineoutputs with amplitude control. Or youcan control the frequency by an externalvoltage (VCF).The Model 195 is completely portable,operated by a 9 -volt transistor battery, soyou can forget 60 -Hertz hum problemsaltogether. An optional rechargeablepower supply and charger permits continuousoperation from Ni -Cad batterypower.This is a true instrument ... developed byby one of the world's leading designersand manufacturers of laboratory functiongenerators and frequency synthesizers.Find out what the Model 195 can do onyour bench, and move up to a bettersource of signals.Price: Model 195 $149.50Optional rechargeable power supply,complete with battery and charger $25.00f.o.b. Hillsboro, Oregon. Instrumentsstocked in 36 locations across the UnitedStates.CIRCLE NO. 8 ON READER SERVICE CARDLam.s+823111111111111111111sr,available. Rise time of the vertical amplifieris 35 nanoseconds, overshoot is 3% or less,and the input impedance is 1 megohmshunted by 35 pF. The.1431 is supplied witha handle /tilt stand, Mylar vector overlay (sothe unit can be used as a vectorscope), butless probe. It is $399.00.CIRCLE NO. 81 ON READER SERVICE CARDFANON TRANSISTORIZED MEGAPHONEThe Fanon Model MV -5S is a combinationmegaphone and warning signal in high -impact plastic bell and housing. Ratedoutput of the amplifier is 5 W with a 300 -ydrange. Unit has a built -in weatherproof,dynamic mike, pistol -grip talk /signalswitch, adjustable volume, and horn alarm.Power is furnished by six "C" cells. $69.95.CIRCLE NO. 82 ON READER SERVICE CARDWe accept BankAmericardand Master Charge.D A flIA EXACTelectronics, inc.(A subsidiary of Danalab, Inc.)BOX 160, HILLSBORO, OREGON 97123(503) 648 -6661 TWX 910- 460 -881113

Read what the experts say aboutHeath kit Digital -Design dolor TVThe picture on theGR -2000 can only bedescribed as superb. TheBlack (Negative) MatrixCRT, the tuner and i -f strip,and the video amplifierprovide a picture equalto that of manystudio color monitors.,,(Popular Electronics, Apri I, 1974)25" (diagonal) Heathkit GR -2000Widely reviewed and acclaimed for its outstandingpicture and years -ahead engineering. At the touchof a button, the channel number appears on thescreen. The optional clock module displays the timeright under the channel readout. The totallysolid -state varactor tuner eliminates noisy "clunkers"with contacts that can wear out. Instead, pressing abutton silently selects any of the 16 pre -programmedUHF or VHF stations. The unique fixed -filter IFnever needs instrument alignment, so pictures retainunmatched clarity and brilliance year after year.And for the ultimate in convenience, add theoptional wireless remote control. The GR -2000 canbe custom mounted and optional cabinets startat $119.95 *.Kit GR -2000, less cabinet, 147 lbs., Exp. /frt.Kit GRA- 2000 -1, Digital clock module, 1 lb., mailableThe picture quality ofthe GR -2000 is flawless,natural tints, excellentdefinition, and picturesare steady as a rock. It'sbetter than any thiswriter has ever seen.'?(Family Handyman, June, 1974)669.95*29.95*The plain truth is, withservice and repair costssoaring even for the mostinsignificant in -homerepair, the GR -2000 is theway all color TV sets willhave to be madein the near future....,,(Elementary Electronics, May -June, 1974)Now -a new generation of Heathkitsmall- screen color TV with digital readoutGR-500 G R -40019" (diagonal) 17" (diagonal)GR-30015" (diagonal) Simulated TV pictures6 unique new Heathkit productsyou can build yourselfHeathkitAM /FM Digital Clock Radio -The GR -1075 is no ordinary clock radio.Big, bright Beckman planar gasdischarge tubes display the time. Thereadouts adjust their brightnessautomatically as room lighting changes.A standby battery power supply keeps the clock ontime (without the display) if the electricity is interrupted.When the power is restored, the 24 -houralarm will be on time -and so will you. You can waketo your favorite station or a gentle electronic "beep"with adjustable volume. And the radio section usesthe same design philosophy as our famous AR -1214Digital Electronic Car Clock /TimerThe GC -1093 is an accurate timepiece for your car, boat orplane. It's an electronic clock and a 20 -hour rally timer, bothwith quartz -crystal accuracy. Bright 1/2" -tall digits dim automaticallyat night. 12 VDC,mounts on or under the dash.Kit GC -10932 lbs., mailable62.95*Dual -Trace OscilloscopeA professional scope at kit -form savings. DC -15 MHz frequencyresponse, post -deflection accelerated CRT, vertical amplifierdelay lines, time base up to100 nsec /cm, guaranteed totrigger up to 30 MHz (typicallyup to 45 MHz), 1 mV/cm vertical sensitivity, trueX -Y capability.Kit 10 -451034 lbs., mailable549.95*stereo receiver including fixed ceramic filters in theAM and FM circuits and a factory -assembled andaligned FM front -end with 5µV sensitivity. With 4IC's, 41 transistors and 35 diodes, the GR- 1075's designis years ahead of ordinary clock radios.Kit GR -1075, less batteries, 10 lbs., mailable, 129.95*Desktop Electronic /Sliderule CalculatorAt last, a sliderule calculator that's big enough to use. The lC-2100 has finger -sized keys and a bright, 1/2"-tall 8 -digit display,Cumulative memory and register exchanges virtually eliminatescratchpad work. Performs arithmetic .:plus trig and arc trig in degrees orradians, common and natural logs,powers of e, square roots, inverses,pi and exponential functions.Kit IC -21004 lbs., mailable119.95*Digital Electronic Clockswith standby powerThe GC -1092A is a digital clock with a snooze alarm; theGC -1092D reads the time in 6 digits, the month and date in4 digits. Both have standby power supplies to keep the clockon time (without the display) even during power interruptions.GC -1092 A & D,less batteries, 5 lbs., mailable each 82.95*Famous Heathkit quality in your choice of screen sizes -15, 17or 19" (diagonal). They all have GR- 2000 -inspired digital channelreadout and optional plug -in clock modules. And in the traditionof the GR -2000, these TV's feature dozens of design innovations.Each uses a precision in -line gun in the picture tube and aslotted shadow mask for a bright picture. The GR -400 and 500'snegative- matrix screen provides superior contrast while luminanceand video circuits with black level clamps maintain thetrue brightness of televised scenes.A factory- sealed static toroid yoke and magnet assembly completelyeliminates convergence and purity adjustments - andthe picture is superior to sets requiring manual adjustments.14The list of significant advances goes on and on - dual gate FETmixer, FET RF amplifier, 4 tuned circuits (instead of the 3 mostsets have), automatic fine tuning and preset picture control, hi -fioutput jack, slide out chassis. The GR -300 and 400 come completewith walnut veneer cabinets, cabinets for the GR -500 startat $39.95.Kit GR -500, less cabinet, 88 lbs., Exp. /frt. 499.95*Kit GR -400, with cabinet, 104 lbs., Exp. /frt. 489.95*Kit GR -300, with cabinet, 90 lbs., Exp. /frt. 449.95*GRA- 2000 -1, clock module for GR -300, 400 & 500,1 lb., mailable ..... ............................... 29.95*POPULAR ELECTRONICSHEATHKIT ELECTRONIC CENTERS -Units of Schlumberger Products CorporationRetail prices slightly higher.ARIZ.: Phoenix; CALIF.: Anaheim, El Cerrito, Los Angeles,Pomona, Redwood City, San Diego (La Mesa),Woodland Hills; COLO.: Denver; CONN.: Hartford(Avon); FIA.: Miami (Hialeah), Tampa; GA.: Atlanta;ILL.: Chicago, Downers Grove; IND.: Indianapolis;KANSAS: Kansas City (Mission); KY.: Louisville; LA.:New Orleans (Kenner); MD.: Baltimore, Rockville;MASS.: Boston (Wellesley); MICH.: Detroit; MINN.:Minneapolis (Hopkins); MO.: St. Louis (Bridgeton);NEB.: Omaha; N.J.: Fair Lawn; N.Y.: Buffalo (Amherst),New York City, Jericho (L.I.), Rochester, WhitePlains; OHIO: Cincinnati (Woodlawn), Cleveland, Columbus,Toledo; PA.: Philadelphia, Pittsburgh; R.I.:Providence (Warwick); TEXAS: Dallas, Houston; VA.:Norfolk (Va. Beach); WASH.: Seattle; WIS.: Milwaukee.JANUARY 1975Send for yourFREE 1975Heathkit Catalog -the world'slargestselection ofelectronic kits!- `-' `1975GC -1092ATime /AlarmGC -1092DrHeath CompanyDept. 10-1Benton Harbor, Michigan 49022Please send my free 1975 Heathkit Catalog.Enclosed is Splus shipping.Please send model(s)NameAddressCIRCLE NO. 5 ON READER SERVICE CARDTime /DateHEATHSchlumbergerCity State ZipPRICES a SPECIFICATIONS SUBJECT TO CHANCE WITHOUT NOTICECL -551NAa oaoFa Panics; F.o. e. FACroar.15

New LiteratureMETHODE ELECTRONICS PC BROCHURE"Printed Circuits," a new brochure fromMethode Electronics is a 16 -page descriptionof various types of printed circuitryincluding single -sided etched and coatedboards, double -sided etched and plated -through types, additive plated- throughholecircuits, and multi -layer and flexibleboards. The brochure is well -illustratedwith explanatory diagrams and photographs.Methode's several multi -panelingconcepts are described: "crackerboard,"scored -array, "nested- array," and web -matrixpanels among them. Address: MethodeElectronics, 7447 W. Wilson Ave. Chicago,IL. 60656.1974 NATIONAL MOS CATALOGThe new edition of National SemiconductorsCorp.'s MOS IC catalog is now available.This latest book contains over 500pages of design and applications informationon the broad National line of standardMOS products, including clocks, calculators,and memories. Complete informationcan be found on National's eight -and nine -digit calculator circuits, digitalclocks for desk -top, alarm and automobileapplications, shift registers -both staticand dynamic, semiconductor memories,including ROM's, PROM's, and RAM's,character generators, code converters,and microprocessor elements. Address:National Semiconductor Corp., MarketingServices Dept., Santa Clara, CA 95051.LAFAYETTE 1975 CATALOGThe latest edition of the Lafayette RadioElectronics catalog is now available freeupon request. It contains over 18,000 itemsin the consumer electronics field includingstereo and 4- channel components andmusic systems, CB, ham, and PA gear, testequipment, antennas and security devices,musical instruments, cameras and optics,calculators, and many types of parts requiredin electronic projects. The format ofthe publication has been changed -pagesize has been increased 45 %; larger typeand more color have been used; audioequipment has ratings in full compliancewith the latest FTC regulations; and majorbrand lines have been given expandedcoverage. The catalog may be obtained at"Quick 'n Easy" Channel Scanningwith ((p)) Pace Sc nning Monitors!SCAN 10 -4 SERIESNew compact design scanner for mobile orbase. UHF model covers 450 -470 MHz, VHFmodel covers 144 -174 MHz, LF covers 25 -50MHz. Each of the 4 crystal channels is tuneable.Either 110 VAC or 12 VDC. Local /distantfunction switch, lockout switches foreach channel, jack for a remote speaker,power cords, mounting bracket and antenna.All of this in an extremely compact size-41/2" x 11/4" x 6 ".PACE Engineers introducethe revolutionary "SCAN -MATE 150." Only 43/4 "high,2" wide and 3/4" thick,SCANMATE 150 scans 4channels in a 10 MHz bandspread within the VHF /hi/FM band. The 4 internal AANicad batteries can becharged with optionalcharger. External or rubberantenna jacks provided.Lockout controls are providedfor each channel.SCAN 150Rubber antennashown is optional.((o)) PACE COMMUNICATIONSDivision of PATHCOM INC., 24049 South Frampton Avenue, Harbor City, California 90710Export: 2200 Shames Drive, Westbury, New York 11590. Available in Canada.16 CIRCLE NO. 27 ON READER SERVICE CARDLafayette stores or write to: LafayetteRadio Electronics, Dept. PR, Box 10, Syosset,NY 11791.AUTHORITATIVE TIME AND FREQUENCY TEXTSA comprehensive collection of information,theory, and data on time and frequency(T /F) standards has been releasedby the National Bureau of Standards.Monograph 140, ($8.65), "Time and Frequency,Theory and Fundamentals," describesthe field of T/F research, from basicconcepts of the measurement of time to thelatest developments in precision timekeepingbased on atomic and molecular resonances.Technical notes supplement the monograph.NBS Technical Note 649 ($1.00),"The Standards of Time and Frequency inthe USA" is also one chapter in the monograph.It describes the activities of the twoagencies chiefly involved in the T/F field-the NBS and the Naval Observatory.Technical Notes 616 (Revised) ($5.70) and656 ($.35) deal with "Frequency Standardsand Clocks: A Tutorial Introduction" and"Standard Time and Frequency: Its Generation,Control, and Dissemination by theNBS," respectively. A discussion of thebroadcasts of radio stations WWV, WWVH,WWVB, and WWVL can be found in thelatter Technical Note. The publications areavailable from the Government Printing Office,Washington, DC 20402.RCA LINEAR IC WALL CHARTAvailable from RCA is a quick- referencewall chart giving data on their linear IC's forcommunications, control, instrumentation,and information systems applications.Included on the chart (Form No.LIC -247A) are op amps, arrays, differentialamplifiers, broadband (video) amplifiers,voltage regulators and thyristor controldevices, AM /FM communications circuits,comparators, and analog multipliers. Italso includes a cross -reference of directreplacement types for the products of 12other manufacturers. Address: RCA SolidState Division, Box 3200, Somerville, NJ08876.1915 RADIO SHACK CATALOGRadio Shack's 1975 catalog (No. 250) describesthe company's complete line ofproducts for home entertainment, hobbyists,and experimenters. The 164 -pagecatalog has 100 full -color pages featuringRadio Shack's own Realistic stereo andfour -channel receivers, automatic turntables,tape recorders and players, speakers,headphones, auto stereos and CB equipment.Other products included are RadioShack electronic calculators, Archer"' antennas,and Archerkittm and Science Fairtmelectronic and hobby kits. Address: RadioShack, Dept. R -20, 2617 W. Seventh St.,Fort Worth, TX. 76107.POPULAR ELECTRONICSMARK TEN B,THE GAS SAVING, PLUG SAVING,TUNE -UP SAVING, ELECTRONICIGNITION FROM DELTA.NOW AS LOW AS 349095.Years of testingand use by racecar drivers in allcategories haveproven Delta'sMark Ten B themost advancedignition systemon the market today.Prove it to yourself. Give you car vr0000miWith a Mark Ten B Capacitive Discharge IgnitionSystem under the hood of your car greatthings will happen ... like reducing costlytune -ups by as much as 75 %. Further, you getbetter all- weather starts, quicker accelerationand better mileage.Many operational problems caused byemission control devices, poor manifolding orimproper fuel mixtures disappear. Delta'sMark Ten B even improves the performanceof brand -new factory installed electronicignitions (Chrysler and Ford). Factory systemsmerely eliminate points and condenser, butthe Delta Mark Ten B combines the advantagesof capacitive discharge with solid stateelectronics togive real performanceandincreasedenergy.Are you a doit-yourselfer?Build your ownMark Ten B ... it'savailable in low -costkit form. Or, if you prefer,get the complete ready -to- installunit. Either way, you can install ityourself in minutes with no rewiring, evenover Chrysler and Ford systems.Mail the coupon today and discover how toenjoy happy motoring with Delta's Mark TenB. The do- it- yourselfer's dream that reallypays off.pvl DELTA PRODUCTS, INC.P.O. Box 1147. Dept. PE Grand Junction. Colo. 81501303 -242-9000H Please send me free literature.Enclosed is $ Ship ppd. Ship C.O.D. Please send Mark Ten B assembled@ $64.95 ppd Mark Ten B Kit @ $49.95 ppd. (12 volt negative ground only) StandardMark Ten assembled, @ $49.95 ppd. 6 Volt: Neg. Ground Only 12 Volt: SpecifyPos. Ground Neg. Ground Standard Mark Ten Deltakir @ $34.95 ppd.(12 Volt Positive or Negative Ground Only)Car YearNameAddressCity /StateJANUARY 1975MakeCIRCLE NO. 12 ON READER SERVICE CARDZipo17

If you've ever said..."There must bbe a better ii.vay to earn a living.::Send for a free Career Guidance Booklet that could start youon the road to success in a rewarding new career.18It happens to all of us, sooner orlater. No matter what kind of job wehave.One day, it suddenly strikes homethat we're going to have to work for aliving, the rest of our lives. And mostof us are horrified at the thought offorever being locked into the jobs wenow hold."Surely," we tell ourselves, "theremust be a way to earn enough extradollars each month to balance thefamily budget. Surely, there must bea way to get the kind of positionwhere you don't have to worry aboutjob security.""Surely," in other words, "theremust be a better way to earn a living!"If you, too, have been thinkingthese same thoughts, you'll find onePOPULAR ELECTRONICSof our free Career Guidance Bookletsvery helpful at this time. We inviteyou to send for one.Your free booklet will describethe opportunities for higher incomeand greater job security you might expectin one of the career fields listedon the coupon and card. It will alsoexplain why ICS can prepare you forthis new career field ...right in yourown home ... in your spare time ...regardless of your education or pastexperience.In addition, you will receive a free"Demonstration Lesson" that lets yousee for yourself why preparing for amore rewarding career -the ICS way-may be a lot easier than you think.Please bear in mind, as you checkoff your career choice on the couponor card, that ICS has a long and distinguishedrecord of success. In fact,since 1890, more than 8,500,000 menand women have turned to ICS forcareer training.Major corporations useICS Career TrainingICS has provided training programsfor various divisions and branches ofcompanies like Ford; U.S. Steel;Chrysler; Mobil; DuPont; etc.ICS Career Training is approvedfor Veterans and Servicemen underthe new G.I. Bill, and is accredited byhe Accrediting Commission of theational Home Study Council.Now it's your turn to discover howS training can start you in a rerdingnew profession. Just fill incoupon or the attached postpaidd and mail it today for your freeer Guidance Booklet and freeonstration Lesson."RY 1975Mail attached postage -free card today. If card is missing, use coupon.r------------------Elld'CSInternational C1Correspondence SchoolsScranton, Pennsylvania 18515XA702QPlease send me a free Career Guidance Booklet, and a free "DemonstrationLesson" for the field I have checked below. I understand thatI am under no obligation.NameAddressEngineeringCivilMechanicalElectricalChemicalIndustrialSurveying & MappingAutomotiveAutomotive MechanicAir Conditioning SpecialistTransmission SpecialistBody RebuildingDiesel /Truck MechanicBusiness ManagementExecutive Mgt.Industrial /Production Mgt.Data Processing Mgt.Marketing /Advertising Mgt.T.V. ServicingColor T.V. TechnicianStereo -Hi -Fi SpecialistCATV -MATV SpecialistElectronicsElectronics TechnicianFCC LicensingComputer ServicingCommunications /BroadcastingElectricianCheck here for special information, if age 16 or underAccountingBusiness AccountantCPA TrainingIncome Tax SpecialistBookkeepingAir Conditioning/Refrigeration/HeatingAir ConditioningRefrigerationHeating SpecialistInterior Decoratingand DesignHigh SchoolICS H.S. Diploma ProgramH.S. Equivalency ProgramDraftingGeneralMechanicalArchitecturalMotel /Hotel ManagementMotel ManagementHotel ExecutiveRestaurant /Club Mgt.Resort ManagementAirline /TravelReservations SpecialistTravel AgentPassenger ServiceCargo AgentCity State ZipTelephone- --- --------- -----JApproved for Veterans' Training. Eligible Institution under the Guaranteed StudentLoan Program. Accredited Member National Home Study Council. Canadian residentsuse Scranton, Pa. address for service from ICS Canadian, Ltd. In Hawaii:931 University Ave., Honolulu, Hawaii 96814. ©t974ICsAptAge21

MIKES AND MIKINGALL RIGHT, you want to buya good microphone so you gofor advice to the experts -the recordingengineers. And a fat lot of goodthat does you! Recording engineerstoday use not one but many microphones,all of which they consider"good" for a particular application.For example, John Woram, a highlyexperienced studio man and professionalconsultant on recording matters,frequently rhapsodizes on thevarious characteristics of mikes inprofessional sound recording magazines.As John tells it, an engineermight want to use a moving -coil mikewith a rather undistinguished high -frequency response to capture a firm,slightly juicy splat from the kick drum(the pedal- operated bass drum in adrum set), while employing a dead -flatcondenser pickup to bring out the dryrustle, sting, and snap of the snaredrum. In fact, a drum set, which reallyconstitutes only one instrument in apop ensemble, may have as many asthree to six different microphoneshovering above, around, or in it.And we can go on. An electric guitaror electric bass consists of the instrumentitself as well as the inductivepickups below each string and theamplifier /speaker conglomerationfrom which the sound emerges. Theengineer has the choice of mikingacoustically through its speaker(which is, after all, part of the "sound"of the instrument), or running a directfeed from the guitar's pickups or amplifiérto the recording console. Onoccasion he's been known to do both,either mixing the two signals on thespot or laying them down in separatetracks on the tape for subsequent mixing.And perhaps he wants to mike theguitar in stereo to give a greater senseof the acoustic field. (Many engineersdo not, preferring to make a mono recordingof the instrument and thencontrol its position in the stereo"spread" by feeding more or less of itto the left or right channel of the final22Stereo SceneBy Ralph Hodgesrecord.) Thus the engineer may use aminimum of three microphones, -ifyou count the guitar's pickups -to getthe sound he wants from onemusician. And today he also has theoption of using nonacoustic devicesthat fasten on the instrument and pickup mechanical vibrations.All of these implements can bebrought to bear selectively, accordingto the way his taste tells him an instrumentshould sound for a particularrecording. Ultimately, recordingstudios acquire reputations for thespecial noises they seem to be able toget, or even for the sympathetic touchthey give certain instruments.Recording studios frequently usemicrophones in an unorthodox fashion.For example, now and again theyput a mike inside the bass drum. Youwouldn't want to do this with one ofthe excellent, but generally fragile ribbonmicrophones of years past, becausethe first thud hitting the diaphragmwould simply blow it away.Few, if any, condenser mikes availablecould stand the punishment withoutdistorting severely. So you take theoverload factor very seriously in professionalrecording work.Many of these considerations are ofno importance for the amateur recordist.You and I do not and never willhave on hand the collection ofNeumann's, RCA's, AKG's, Senn -heiser's and now Sony's that the bigstudios can inventory. We work withtwo or three mikes at maximum, hangingthem out in space where they'renot likely to get overloaded by any oneinstrument, and we record the performanceas an ensemble effort, notas individual instruments.For these purposes, I favor the flattestfrequency response possible in amicrophone. This is not the obviouschoice that it first appears to be, andit's possible that many amateur recordists(and certainly many pros) woulddisagree. For example, a mike intendedfor close -up work, especiallyfor voice, might have a gradually descendinglow- frequency response,and perhaps a bump in the uppermid -range. These characteristics,compensate for an emphasis of lowsthat most directional mikes exhibit atclose range ( "proximity effect "), andalso improve articulation. Fine, but I'musually out in the boondocks worryingabout anything but proximity effects.Now and again, I do feel a need forthe mid -range bump (often called"presence boost ") and wish I had it.But under my normal working conditions(frequently my first hearing ofthe music comes when the tape startsrolling and the performance begins), Ihave neither the time nor inclination tomess with such esoterica. (I shouldmention that proximity- effect compensationand even presence boostcan be cut in or out by switching onthe cases of some microphones.) So Iprefer flat frequency response, for thekind of recording I do.Frequency Response. Fre-quency- response data for a microphonecan be obtained by measuringits simple electronic output with ameter. You don't have to mike a complexacoustic field as you do with aspeaker. But microphone and speakertesting share a common problem: likespeakers, microphones are directional,sometimes by accident (diffractioneffects of the case on sound tryingto reach the diaphragm, for example)and often by design. The two mostcommon microphone directionaltypes in the amateur's inventory arethe omnidirectional, meaning a mikethat responds equally to sounds impingingfrom all directions (or tries to,anyway); and the cardioid, which describesa microphone that attempts torespond fully to sounds in front of it(wherever its front happens to be) andnot at all to sounds approaching frombehind it. The polar graphs in Figure 1illustrate these pickup patterns; imaginethe circle of the omni to be a fullsphere, and the cardioid's pattern as aripe tomato viewed from the side.Why would you use a directionalmicrophone like a cardioid? Obviously,you'd use it if you didn't likesomething coming from behind. Thiscould be audience noise or room/concert -hall reverberation, particularlyif it echoes, sounds otherwisenasty, or is just excessive.There are other directional types,too, such as the bidirectional,exhibiting a figure -eight polar re-POPULAR ELECTRONICSSorry, but when it comes to ournew Phase Linear 4000, modestyfails us. How else would youdescribe a preamplifier that actually:Puts back in whatrecordingstudios take out.Restores dynamics lost inrecording to closely approximatethe original.Vanishes into virtual inaudibility allhum, noise and hiss inherentin most tapes, records, andFM broadcasts.Lets your music (at last) reacha life -like level where cymbalssound like cymbals, kettle drumslike kettle drums.Lets you ... for the first time ...hear your music from asilent background.Since its introduction follows thePhase Linear 700 and 400 poweramps, the 4000 pre -amp had to begood. Consider these features:The Peak UnlimiterTo prevent overload in recordingequipment, studios today "peaklimit" high -level explosive transientsof the source material. Incorporatedin the Phase Linear 4000 is ahighly- advanced circuit that reads.peak limiting, immediately routesthe signal through a lead network,and restores dynamics lost inrecording to closely approximatethe original.'So is a trademark of CBS Labs, Inc..f' /.n «..Yï. rn.Siri ,k11)° -Incredible.The Downward ExpanderGain riding, a recording techniqueused to improve low level signal tonoise on phonograph discs,unfortunately compresses dynamicrange that would otherwise beavailable. The 4000 senses whengain riding has been used andimmediately expands the dynamicsreciprocally downward to preciselythe intended level.The AutoCorrelatorThe advanced AutocorrelationNoise Reduction System in the4000 makes record /tape hiss andFM broadcast noise virtually vanish... without effecting musical contentof the source material. Over -all noisereduction is 10 dB from 20 Hz to20 kHz. Your music comes from abackground that is silent.Plus ...... the 4000 is an advanced stereopreamp with SC)* and Phase Lineardifferential logic ... its ActiveEqualizer gives you a truly flat energydistribution over the full audiospectrum ... completely passive,independent,Step -Tone Controlsallow precise tailoring of the musicto your listening environment.It is, in a word, incredible. Ask yourdealer for an audition.LPHASE LINEAR 4000 SPECIFICATIONSTotal Distortion: Less than .25 %.Typically .02 %.Total Noise: High level: 83 dB below2 volts. Phono: 72 dB below a 10millivolt reference.Tone Controls: Bass: Monotonicallyincreasing and decreasing, dual hingepoints, ± 8 dB @ 20 Hz. Hinge pointsswitch selectable beginning at 40 Hzor 150 Hz..Treble: Monotonicallyincreasing and decreasing, dual hingepoints, ± 8 dB @ 20 kHz. Hinge pointsswitch selectable beginning at 2 kHzand 8 kHz.Active Equalizer: 6 dB /octave boostbelow 50 Hz.Peak Unlimiter: (Nominal peak unlimitrate attack threshold, front panelvariable) .5 dB /micro second for + 6 dBpeak unlimited operation.Downward Expander: Downwardexpansion commences at -35 dB.Ultimate limit is -41 dB. Unlimiterwindow is 35 dB wide, upper and lowerthresholds are simultaneously variable.Auto Correlator (Noise ReductionSystems): High frequency noise reductioncommences at 2 kHz and is 3 dB,reaching 10 dB from 4 kHz to 20 kHz.Weighted overall noise reduction is-10 dB from 20 Hz to 20 kHz.Size: 19" x 7" x 10 "- Weight: 18 lbs.Warranty: Three years, parts and labor.i%ae £&)níw4 4000THE POWERFUL DIFFERENCEPHASE LINEAR CORPORATION, P.O. BOX 1335, LYNNWOOD, WASHINGTON 98036CIRCLE NO. 28 ON READER SERVICE CARD

D'Fig. 1. Mike pickup patterns: (left)olninidirectional; (right) cardioid.sponse (or, to continue the three -dimensional analogies, a crudelyformed dumbbell with no place tograb onto), and thesupercardioid andhypercardioid varieties, which narrowthe cardioid's tomato down into apepper (sometimes even a chili pepper)shape, usually with some leafygrowth at the stem indicating less thantotal success in eliminating rearwardsounds. Some of these are beloved byprofessionals, either for their pickuppatterns or for other special qualities.But they are rarely part of theamateur's equipage.Back to frequency response. Thesound -output pattern of a loudspeakercan also be shown with polarplots. But as any casual audiophileknows, the polar pattern will not be thesame at all frequencies. Lows tend tobecome omnidirectional, while highsmay begin to "beam" in a tight super-I ,o°ft300°/ 60°90rr,/270°h.',,.id%wry/1240° 120°210° 150°IBO°SCALE IS 5 DECIBELS PER DIVISIONA. 5kHxB. I kHzC = 50014.Do 100HzFig. 2. Cardioid pickup patternsat four different frequencies.cardioid fashion. So it is with microphones,although their directionalaberrations are not always the same.Figure 2 shows the polar plots for acardioid mike at several different frequencies,while Fig. 3 gives its variousfrequency responses for soundsoriginating at zero degrees (right infront, or "on axis "), and at several anglesoff axis. If the polar plot of Fig. 2showed the pickup patterns for all fre-24quencies, you could draw Fig. 3 directlyfrom it.What does all this mean? Well, asyou may know, the frequency responseyou hear from a speaker in aroom is a combination of its numerousfrequency responses at various angles,since reflections from roomboundaries ultimately bring to yourears the speaker's output at 60 degrees,90 degrees, 180 degrees, etc.And the frequency response of a microphone(i.e., what it "hears ") is alsoa composite of its various responsesat all angles, since it's picking up thesame sort of room reflections.It follows (or so it seems to me) thatthe real frequency response of a microphoneis not the simple on -axiscurve, but some kind of summation ofthe curves in Fig. 3 and many othersbesides, all adjusted for the reflectivityof the particular recording environment.But since you can't predict thenature of the recording environment,you're ultimately best off, I'd imagine,with a mike whose response changeslittle with incident angle. The microphoneof Figs. 2 and 3 is not toobad in this respect. Others will be betterstill, and some will be worse. Andfor some microphones you may be interestedin, the relevant data of thiskind will prove difficult to get, I'mafraid, even from the manufacturer.But we all do our best.oMicrophone Types. There areonly three microphone types that interestthe serious recordist: movingcoil, ribbon, and condenser. The movingcoil closely resembles a speaker(and especially a dome -type tweeter)in construction. In operation its cone(or dome) is shuttled to and fro by impingingsound, and the magnet assemblyinduces an output voltage inthe coil that moves with it. The ribbontype employs a low -mass diaphragmof corrugated metal foil that is also theinductor as it moves within a magneticfield. Condenser microphones consistof a light diaphragm in close proximityto a conductive plate. The diaphragmis polarized- either by an external dcvoltage source or with a built -in (electret)electrostatic charge -and as itmoves relative to the stationary platein response to air -pressure changes,the varying capacitance modulatesthe output voltage.The time was when the high -frequency responses of these threetypes were a function of their diaphragms'inherent moving masses,and ranged from dismal to marginal(moving coil), better (ribbon), and best(condenser). Improved materials andconstruction have made remarkablestrides in narrowing the gap, so thaton a dollar- for -dollar basis you canget perfectly acceptable -if notidentical -results from any. Of course,ribbon mikes are complex in constructionand not really available below$100 apiece. But at around $150 youmight well pick a ribbon over movingcoil or a condenser.Then there is the question of ruggednessand resistance to acousticoverload. To my knowledge I've neverhad a mike physically overload, butthen I don't work close up as a rule. Ifyou plan to, then you should know thatmoving -coil types are considered bestat shrugging off the very high sound -pressure levels that come from brass,drums, electronic instruments, etc.ézot''5dBTL20i.iiiIlw1\0°IIII`.ñ19° WWIIIlrirllwliIe0°Iill1-1111!I I v1\50 IOO 500 IKFREQUENCY (Hz)Fig. 3. Cardioid frequency responseon axis and at two angles off -axis.5K IOK 20KSome condenser jobs come fairlyclose, but few condensers can alwaysbe trusted in these applications. Ribbonsused to have a terrible reputationfor going mechanicallyto pieces at theslightest provocation, and sometimessuffering permanent injury. Many ofthe breed are still quite delicate, butBeyer claims that its ribbons can toleratesound -pressure levels in excessof 130 dB -well into the moving -coilclass; and the Group 128 condensermikes are said to be equally rugged.As for directional properties, moving-coil and condenser mikes can bemade to exhibit practically any pickuppattern. The same is theoretically truefor ribbons, but I don't know of anyomnidirectional ribbon mikes.Incidentally, lest I have frightenedanyone away with my brief referenceto prices above, let me say that finemoving -coil and electret- condensermikes can be had for $50 and less.Impedance, Sensitivity, Etc.These topics frequently form the bulkof microphone how -to -buy articles. Iplan to give them very short shrift.POPULAR ELECTRONICSIt is imperative, when using longishmicrophone cables, to set yourself upwith low- impedance mikes, whichavoids certain noise and high -frequencyloss problems. Recognizingthis, every modern tape- recordermanufacturer can think of has de-Isigned his microphone inputs for low -impedance mikes ( "suitable for microphoneimpedances from 150 to 600ohms" is a typical "specification ").Almost any microphone with true audiophileappeal is going to be availablewithin that range. Some can beswitched to higher impedance.Sensitivity (which is voltage out, forsuch -and -such a sound- pressurelevel, into such -and-such an impedance)is trickier. I like a high- outputmike because, again, I prefer to keepmy microphones somewhat awayfrom the instruments, and sound -pressure levels are lower out there.Therefore I'm often happiest with acondenser, which has and needs itsown amplifier (often built into the microphonecase these days, and poweredby an integral penlight dry cell).Thus, a condenser can have just aboutany output it pleases, and it may notcare alot about load impedanceeither. (But there is an additional noisespecification -the noise contributedby the microphone's amplifier -toconsider.) Mikes with excessively lowoutput would get me into signal -tonoisetrouble with my recorder'spreamps, however. And excessivelyhigh outputs might get the close mikerinto trouble, since the microphone inputsof most audiophile recordershave electronics before the record -level controls, and these can overload.But a passive attenuator consisting ofa simple resistor network -availablefrom Shure, Electro- Voice, andothers, installed in a case for easymicrophone line insertion -will takecare of that.Few desirable microphones inrealistic (for us) price ranges vary somuch in output from the norm that away couldn't be found to make a decentrecording of, say, voice andacoustic guitar. But when you try todiscover the optimum mike for yourmachine, you find you need noise andoverload data for your microphone inputs,comparable sensitivity specs fordifferent brands of microphone (andthey're not really comparable at present),and some very difficult -to -get (orbelieve) data about live -music levels.(Argh!) Instead, I recommend youconsult your tape machine's manufac-JANUARY 1975turer. In many cases he'll have had achance to use the mike that interestsyou, and has some insights.Contacting the manufacturer couldbe particularly helpful if you plan amajor purchase. But don't just writeand say, "Which microphone should Ibuy ?" Familiarize yourself with what'savailable, narrow your choices downto a few, and let him suggest a finalhopeless. Who cares? I'm in businessto please myself, not the mass millions.I get the kind of sound I wishcould get on more commercial recordings,and that is the reason willinglylug tape machine, mikes, headphones,mike stands, cables, andmiles of tape through dark Manhattannights in quest of musical events.For like- minded souls wishing todecision in the light of your expressed learn about microphones, I can rec-(in your letter, concisely) recording in- ommend Lou Burroughs' Microtentions.phones: Design and Application,As I've said, I prefer to mike a little from which I've freely borrowed fordistantly. This is because I get a gooddose of hall reverberation mixed intothis column and its illustrations. Itcosts an outrageous $20 (plus tax andthe final result, and since being well postage, I'm sure) from Sagamoreback in the hall is the perspective from Publishing Co., 980 Old Country,which I'm used to hearing perfor- Road, Plainview, N.Y. 11803, but it is amances, it sounds truer to me. (By the truly fine and comprehensive text,way, when I say "mike distantly," it with revelatory advice on maintemeansthat the microphones are usu- nance.ally at stage edge or a little beyond,and from seven to twelve feet up.) Correction. An error appeared inget all kinds of arguments about my November 1974 column onImy technique, and I pay them no attentionwhatever. True, my tapes wouldbe too dim and muddy for AM radioplay (although I absolutely insist theysound fine through good speakers);and for most commercial purposes,they would probably be consideredspeaker failure. In the discussion ofwoofer -cone offset, the text referredto dc amplifier voltages that "may appearat the output capacitors." Thesentence should have read, "may appearat the outputs of direct -coupledamplifiers using no capacitors."Model AT15S cartridge shownin Model AT1008 tone arm.THET TIPIS SHIBATA...andaudio -technics!The only phono stylus tip designedfor lower record wear whileimproving high frequency tracing.It's the stylus we include on ourAT12S, AT14S, AT15S & AT2OSLAudio -Technica Dual Magnet*audio technica.cartridges. To give youbetter sound from anymatrix record or presentstereo disc, as well ascorrect, long- lasting performancefrom discrete4- channel (CD-4) records.Audio -Technica Dual Magnetcartridges arebrand new andloaded with features. Like a separate,independent magnetic systemfor each side of the stereogroove. And smooth response to45,000 Hz and beyond. Plus verylow moving mass for superior tracingability.Get a tip from leading audioshowrooms throughout thecountry who are now stockingand recommending the Audio -Technica Dual Magnet cartridges.For every modern record you own.*U.S. Patent Nos. 3,720,796; 3,761,647AUDIO -TECHNICA U.S., INC., Dept. 15P, 33 Shiawassee Ave., Fairlawn, Ohio 44313In Canada: Superior Electronlcs, Inc.CIRCLE NO. 6 ON READER SERVICE CARD25

HIGHLIGHTSrPhilips & MCA Market Video DiscN. V. Philips, based in the Netherlands, and MCA,Inc., Los Angeles, have reached an agreement for marketinga Philips /MCA video -disc player and compatiblediscs for consumer use. An official of MCA states thatthis development will result in the interchangeability oftheir video discs. The companies will establish a licensingorganizatiori to negotiate with others for related patents.It is expected that a liberal licensing policy willenable many companies to participate in the videoplayer technologies of both concerns. The Philips /MCAvideo-disc player will be manufactured and marketed byPhilips, while MCA, whose resources include the UniversalPictures film library, will produce and marketvideo disc programs.Blank Tape Sales SkyrocketingNearly 200 million blank cassette tapes and 30 millionblank 8 -track cartridges will be purchased thisyear, according to the Longines Symphonette Company,a major producer of such tapes. The companyalso states that cassettes, though now considered a hi -fimedium, are being used for speech recording as well asmusic. Students are recording their lectures, andbusinessmen are taping their conferences on cassettes.These new demands, according to a Longines sales projection,will push the total cassette purchases in 1976 totop 340 million. This represents an increase in sales atthe rate of 50 million more new cassettes per year.RCA Introduces Hybrid OP AmpsRCA's Solid State division has introduced a family ofhybrid op amps that combine the advantages ofMOS /FET's, bipolar transistors, and COS /MOS on amonolithic chip. Gate -protected PMOS transistors areused in the input circuits of the CA3130 family, to providevery high input impedance, low input current, andhigh -speed performance. The common -mode input -voltage range goes to 0.5 volts below the negative -supply terminal. A bipolar driver provides voltage gain.A COS /MOS drain -loaded inverting amplifier comprisesthe output stage operating in the Class A mode. Theoutput can be swung within millivolts of either supplyrail when used with highly resistive loads, and the gainof this stage depends on the load impedance. Open loopgain of the op amp is 110 dB and bandwidth is 15 MHz.The CA3130 series can be used as comparators(COS /MOS interface), wideband amplifiers, voltageregulators and followers, and in timing applications.Data Transmission on Real -Time TVA new system of encoding information on broadcastTV signals has been introduced by the Atlantic ResearchCorp., Alexandria, Va. The Data -Dottm systemmodifies the video signals to cause a small dot to appearin a corner of the receiver's screen, which carries one ormore channels of information. A peanut -sized opticalsensor is placed over the dot, and decodes the informationwhich can be printed, displayed, or recorded by avariety of terminal devices. The manufacturer says thatmodules can be used without any modification of theTV receiver. This system has many possible uses. It canprovide data to accompany any televised event -performancerecords of a player involved in a sports competition,historical information on dramatic characters,even stock market and news reports!"Under New Proprietorship"GTE Sylvania and Philco -Ford jointly announced anagreement under which the former would acquire thePhilco name and distribution rights for home entertainmentproducts manufactured by Philco- Ford'sHome Products Division, and sold in the U.S. andCanada. The agreement does not involve Philco- Ford'sline of home refrigerators and freezers, its Telesoundoperations, or its automotive products. In another development,North American Philips Corp. acquiredabout 85 percent, or 15 million shares, of the outstandingstock in the Magnavox Company.Trends in the Microwave IndustryThe microwave products industry represents 8 percentof the total electronics industry, and generates$2.2 billion annually in economic activity. This figure isexpected to grow to $2.8 billion by 1983, according to areport assembled by the Business CommunicationsCompany, Stamford, Conn. A large (7.5 percent) annualgrowth is predicted for the microwave oven field.Private -Use TV StationA new television station, available for private use, hasopened in New York City. It is part of a new serviceauthorized by the FCC, called Multipoint DistributionService. The new medium, named "Private Television,"is to be utilized by business, government, and entertainmentusers to deliver their programs at lower costthan is possible via other available means.... Ownedand operated by the Microband Corp. of America, thestation has its control center located in the Empire StateBuilding and will provide its full -color private TVtransmission facilities to various locations throughoutthe tri-state area. ... The station comes under FCCcommon -carrier regulations, which restrict its activityto program distribution only. Customers select thetransmission time, as well as the individual receivingpoints, and control the program content. Multiple DistributionService (MDS) uses microwave frequencies(215Q MHz) and a system of address -encoding to assureprogram privacy.... Microband is affiliated withMDS stations in other cities through a national systemthat plans to use domestic communication sattelites tointerconnect them in a national private TV network.Stations are presently in Washington, D.C., Chicago,Houston, Baltimore, and Philadelphia. Coverage forMiami is expected soon.Our 25 Ib., $2000.00four channel scope ishandheld, digital,weights 10 ozs.and costs $189.50*The mitScope MS -416 is a valuable tool in analyzing circuits.With the increasing use of digital circuitry in home entertainmentequipment (stereo receivers, television sets, etc.). the MS-416will be indispensable for every electronic service department.Digital circuitry is becoming more and more commonplace, andthe mitScope is designed to handle this requirement. The MS -416can be extremely useful in digital circuit design in electronicresearch and development situations. With its memorycapability the mitScope can outperform oscilloscopes manytimes its price.A few of the areas where the mitScope is an excellent tool for diagnosing problemsare: electronic calculators; digital clocks and timers; digital automotive electronics:and many more.DISPLAY: LED Matrix: 4x16 LED Matrix. 4 channels:with 16 divisions per channel useful for determiningextensive time relationships.TIME BASE: Range: from .5 u sec. to .2 sec.Triggering: from channel one input signal; positiveor negative edge selection using SYNC switch; alsoan automatic sweep for checking DC steady -statesignals.Range Selection: using three controls -a potentiometerfor initial sweep rate and two switches forX1000 and X20 selection.* OR, IF YOU REALLY WANT TOSAVE, BUILD YOUR OWNMS -416 FOR JUST $127.50Warranty. One year on parts andlabor on assembled units. 90 dayson parts for kits.Prices, specifications and deliverysubject to change without notice."Creative Electronics"eq..e..a+MS"416SIZE: 5 3/4 "x 3 1/4" x 1 1/4"MODES: Normal: for most troubleshooting andtesting applications. Storage: on all 4 channelsstores the information in a 16x4 bit high speed RAMand displays the signal continuously.PULSE CATCHING: Single -shot storagecapability: can catch and store a one -time occuringpulse in the memory and display it for as long asdesired.POWER: Battery: operation using rechargableNiCads. AC: operation using an AC- (Adapter/Charger) for use with normal 110 v.a.c.PRICE: MS-416 (fully assembled) $189.50MS -416 (kit with easy -to- follow manual) $127.50IU Enclosed H a Check foror BankAmericard #or Master Charge #Credit Card Expiration DateOKitInclude $3.00 for Postage and Handling AssembledMS-416Please sand information on Entire MITS Line.NAMEADDRESSCITYSTATE L ZIPMITS/ 6316 Linn, N.E., Albuquerque, New Mmico 67708 505/2657553PE-1-75ti26POPULAR ELECTRONICSJANUARY 1975CIRCLE NO. 24 ON READER SERVICE CARD27

amSylvania goes one better.We train you on two TV'sinstead of one(You keep both)12" Black & WhiteWith Sylvania's MasterTV Career Program,you get not just one but twoTVsets. Color and Black & White. Bothsolid- state. Both designed to give youthe solid, practical experience youneed. Both yours to build, learn withand keep.With all Sylvania Career Programsyou get our exclusive Autotextmethod of instruction, a modern,step -by -step approach to learning,which gets you through the basics ofelectronics quickly and easily.An optional Cassette System, atechnique that adds an extra dimensionto learning. It's almost like having aninstructor right in your own home. Asyou play the tapes, he'll guide youthrough your lessons, explaining asyou read, going over schematics andreinforcing everything you learn!Plus a choice of Programs thatcan lead to any number of careergoals.In TV, communications, automation,digital and solid -state electronics. Andin fields you haven't even dreamed of.Plus specialized advanced trainingand carefully -engineered ProjectKits for that "hands -on" training youneed to make it in the world ofelectronics.Throughout your training,Sylvania makes that extra effort to goone better.Send the card or mail in coupontoday for our FREE Catalog. Andgo with Sylvania.r SYLVANIA Technical Schoolsl Home Study Division 694 -501 -0Sylvania Technical Systems, Inc.909 Third AvenueNew York, N.Y. 10022Please send me FREE illustrated careercatalog. I understand that I under noobligation.NameAddressCityStateAgeVeterans: Check hereZipL- --Co'o, cabinet optionalSYLVANIAJlIJANUARY 1975POPULAR ELECTRONICSCIRCLE NO. 16 ON READER SERVICE CARD31

AlJ5 PEIUO TO flNNUL]NIE:THE CT-LONTEFilliNfiL YTE1* DISPLAYS UP TO 16 LINES (of 32 Characters) AT ONE TIME.* 1,024 Character - Two Page Memory Capacity - STANDARD.* Plug -In Circuits to adapt the terminal to any requirement at lowest possible cost.* Requires +5 Volts DC @ 2.5 Amps, -5 and -12 Volts @ 20 Ma.* Use with any TV setPopular ElectronicsJANUARY, 1975EXCLUSIVE!ALTAIR 8800The most powerful minicomputerproject ever presented -can be builtfor under $400At last we can tell you about the most versatile, video -display terminal kit available anywhere; the SouthwestTechnical CT -1024. Our terminal is designed around a basicmother board and a 6,144 bit memory that will displaytwo pages of data on any standard television set, or monitor.The two pages consist of 16 lines with 32 characters oneach line. Input may be any source of parallel ASCII code;keyboard, computer, etc. If the system is to be used for adisplay, teaching aid, deaf communicator, or other similarpurpose; this is all you will need.Other applications of a terminal system such as remote timeshare, RTTY, etc require an interface having a serial output.For these applications you add our# CT -S plug -in UARTcard to the mother board. This allows you to transmit andreceive ACSCII coded data in serial form at a rate of 110baud. (300 and 600 baud options are available). Thestandard RS -232 type interface connects directly to yourtransmitter FSK modulator, modem system, or what haveyou.If you are going to use the CT -1024 directly with a computerI/O port that requires a parallel ACSCII input, thenyou will want our parallel interface card, #CT -P which32* Up to date, low power consumption STATIC type MOS Memory.* No complicated refresh or power -down circuits needed.allows either the keyboard, or the computer to access theterminals memory and display data on the screen.For those applications where it is useful, we also have an"off line edit ", or "screen read" plug -in circuit #CT -E.This allows you to compose a program, or message on theterminals display screen and transmit it out a line at a timewhen you are finished and satisfied that everything is correct.If you would like the convenience of complete cursor control,we have our # CT -CM plug -in board. This gives youMove Right, Move Left, Move Up, Move Down, Home Up,Erase to end of line and Erase to end of frame functions.These are operated by keyswitches, or any other typeswitches you may wish to use, giving you complete manualcontrol of the cursor.If the terminal is to be part of a computer system, youmight prefer our automatic cursor control circuit #CT -CA.This plug -in not only allows you to control the cursor andto perform the functions listed above, but makes possiblecomputer control of these same functions through themachines software.# CT -1024 Terminal System Kit with 1024 Memory Card -less cabinet or power supply $175.00 PPd$ 17.50 PPd# CT -E Screen Read Plug -in Card Kit# CT -M Manual Cursor Control Plug -in Card Kit# CT -P Power Supply for CT- 1024 -115 -230 Volt Primaries# KBD -2 Keyboard Kit - 53 KeysFREE -1975 Catalog -Circle our number on the "Bingo" card$ 11.50 PPd$ 15.50 PPd$ 39.95 PPdSOUTHWEST TECHNICAL PRODUCTS CORPORATION219 W. RHAPSODYSAN ANTONIO. TEXAS 78216CIRCLE NO. 34 ON READER SERVICE CARDPOPULAR ELECTRONICSALTAIR 8800THE era of the computer in everyhome -a favorite topic amongscience -fiction writers -has arrived!It's made possible by the POPULARELECTRONICS /MITS Altair 8800, a full -blown computer that can hold its ownagainst sophisticated minicomputersnow on the market. And it doesn't costseveral thousand dollars. In fact, itsin a color TV- receiver's price class-under $400 for a complete kit.The Altair 8800 is not a "demonstrator"or souped -up calculator. It isthe most powerful computer ever presentedas a construction project in anyelectronics magazine. In many ways, itrepresents a revolutionary developmentin electronic design and thinking.The Altair 8800 is a parallel 8 -bitvord /16 -bit address computer with aninstruction cycle time of 2 ps. Its cen-ANUARY 19759I0 M(1N IIt MI 001 0(,A 91pCN 010 INf AT p a 04 N 90 O, Po- ' '.i -:3,A101i611 31911 615 MA A13 Al, 41. 0,0 A9 A0 A *1Ps 11 13 1] 1 15 0 / 7 e í 1wA5 11 At Al-AO3 1 I 011330MOP 1,tC (1AY9J FOxtral processing unit is a new LSI chipthat is many times more powerful thanprevious IC processors. It can accommodate256 inputs and 256 outputs,all directly addressable, and has78 basic machine instructions (ascompared with 40 in the usualminicomputer). This means that youcan write an extensive and detailedprogram. The basic computer has256 words of memory, but it can beeconomically expanded for 65,000words. Thus, with full expansion, up to65,000 subroutines can all be going atthe same time.The basic computer is a completesystem. The program can be enteredvia switches located on the frontpanel, providing a LED readout in binaryformat. The very -low -cost terminalpresented in POPULAR ELEC-TRONICS last month can also be used.BY H. EDWARD ROBERTS AND WILLIAM YATESPROCESSOR DESCRIPTIONProcessor: 8 bit parallelMax. memory: 65,000 words (all directlyaddressable)Instruction cycle time: 2 ps (min.)Inputs and outputs: 256 (all directly addressable)Number of basic machine instructions:78 (181 with variants)Add /substract time: 2 psNumber of subroutine levels: 65,000Interrupt structure: 8 hardwire vectoredlevels plus software levelsNumber of auxiliary registers: 8 plusstack pointer, program counter andaccumulatorMemory type: semiconductor (dynamicor static RAM, ROM, PROM)Memory access time: 850 ns static RAM;420 or 150 ns dynamic Ram33

34ADDRESSCPUMEMORYDATA BUSS `'INPUTOUTPUTFig. 1. Basic blockdiagram of computerparts and operation.In an upcoming issue, we will describehow to build a low -cost CRTtypeterminal that can be used with thecomputer and can also be mated withany time -sharing computer by telephone.matter) is shown in Fig. 1. It consists ofthe following subsystems:CPU. The heart of the computer isthe CPU, or central processor unit.See fig. 2. The CPU performs all thecalculations, generates system timing,and makes all decisions. Of particularimportance are the decisionsthe CPU makes concerning what deviceshould have access to the databuss. It makes these decisions bysending status information at the beginningof each computer cycle, tellingthe memory and the input /outputwhat to expect for the rest of the cycle.The CPU contains the programtimer, sometimes called the P counter.This device keeps track of the currentlocation in the memory that the processoris using. Also located in the CPUis the arithmetic unit.The CPU used in the 8800 computer,the Intel 8080 LSI chip, is relatively expensivein quantities of one. It wasselected, however, because it servesPARTS LISTC1, C5 to C13- 0.1 -µF disc capacitorC2- 0.01 -µF disc capacitorC3, C4- 100 -pF disc capacitorC14 to C20- -0.001 -µF disc capacitorICI -8080 central processing unit IC(Intel)IC2 to IC5 -74L74 ICIC6 to IC 14 -8T97 ICIC15, IC17 7402 ICIC16, IC32, IC33 -7404 ICIC18 to IC20, IC51 74123 ICIC21 -7473 ICIC ;2 to IC24, IC50 -7400 ICIC25 -7430 ICIC26 -7410 ICIC a7 to IC31, IC39 to IC41 -7405 ICIC34, IC35 -8111 ICIC36 -74L30 ICIC42 to IC49 -74L00 ICIC52 -7406 ICIC53 to IC58 -8111 IC (optional)L Li to LED36 -Panel -type, red light -AbouttheComputer.A computer is to create a minicomputer whose per - emitting diodebasically a piece of variable hardware. formance competes with current Note: Following are resistors 1 -watt,By changing the bit pattern stored in commercial minicomputers. In prac- 10% tolerance)R I, R3, R9 to R31, R56 -1000 ohmthe memory, the hardware (electronic tice, a lower- performance processorR2, R4, R7, R8-330 ohmcircuitry) can be altered from one type would have been adequate for the ma-R5, R33 to R37 -2200 ohmof device to another. When the bit pat- jority of the tasks the user might wishR6 -7500 ohmtern, and thus the hardware, is to initially define .But the problem with R32 -100 ohmchanged, we have what is referred to the lesser -power approach is that rela- R38, R48 to R55- 10,000 ohmas "software." Any type of variable in- tively little money would be saved, and R39- 200,000 ohmstruction (programming)-such as it would be doomed to near -future ob- R40 to R47 -470 ohmBasic, Fortran, Cobol, Algol -is gen- solescence for practical purposes. R57 to R92 -220 ohmerally classified as software.Our intent here was to produce a SI to S16, S25 -Spst miniature toggleswitchTo cause it to vary the hardware, you processor with more than enoughS17 to S24 -Spdt spring -loaded, momenmustcommunicate with the compu- power to handle any job.ter. In the case of the 8800, this is done Still another consideration was tary- action miniature toggle switchXTAL -2-MHz crystalby setting the bit pattern on the front- programming. The larger the instruc- Misc. -Metal case; power supply (seepanel switches in accordance with a tion set, the easier the computer is to text); line cord; multiconductor ribbonset of instructions (provided with the program. The 8080 chip has 78 in- cable; mounting hardware; solder; etc.Intel 8080 LSI chip). For example, the structions, which is almost twice that Note: The following items are available8800 computer will automatically add of the next power level CPU available from MITS, Inc., 6328 Linn N.E.,when a specific bit pattern (10000010) (Intel's 8008), which is really designed Albuquerque, NM 87108 (Tel.: 505-265- 7553): partial kit No. 8800PK (inisreceived. By setting address and for use as a buffer.data switches, a complete program of The CPU contains eight general -cludes pc boards and all electronic components(but not case, switches, orup to 78 steps in the basic computer purpose registers, P counter, arithmecanbe inserted into the processor. If tic unit, accumulator, power supply), $298; complete kit No.stack pointer,8800K (contains all parts, includingextensive programming is to be per- instruction decoder, and miscellane- ready -to-use case, switches, and powerformed, an assembler or higher Ian- ous timing and control circuits. The supply), $397; Completely assembledguage is used. With an assembler, the arithmetic unit is of special interest and tested Model 8800A computer (inpersondoing the program simply because it contains the circuitry re- cludes 90 -day warranty), $498. Prices dotypes the word "add" on the device. quired to perform arithmetic in both not include postage or delivery charge.(In Basic and Fortran, a + is used in- decimalformats.Both kits include detailed assembly andThe stack binary egister that operating manual. A FREE set of etchstead.)Fundamental programming con- keeps track of the subroutine ad- ing and drilling guides, component -placement diagrams and miscellaneouscepts are simple enough to master in a dresses. The 8800 computer is capainformationis available from the kit suprelativelyshort time. However, to be- ble of performing an almost unlimitedplier (send self -addressed 81/2" x 11" encomean efficient programmer re- number of subroutines, a feature not velope with 40c postage). Check supquiresa lot of experience and a large available with other microprocessors plier or manufacturer for latest ICIamount of creativity.and absent in many minicomputers. price, available separately.The block diagram of the basic 8800 The instruction decoder is the corecomputer (or any computer, for that of the variable- hardware concept. ItPOPULAR ELECTRONICSWKWX;CJzaip a -á«o.-031FHWz 4Koo.zWFó3-NmWUcW2-JREGISTERO-Wm-UzÑ_ZgaQFtozWZ00UOKa.SELECT fiFig. 2. These are logic functions on the 8080processor chip (ICI). This n- channel CPU permits78 basic instructions and has 8 -bit parallel processing.FrcQWRm r mQa K WDR FU)a a - f f=UJaJWW2ooZao

A95A15D95D7ICI808014)2SYNCDBINWAITWRHLDAINTEREADYHOLDINTRESET-- +5V-5V+12VTO RESETCLOCKIC6-ICIC8,IC9IC16C.>+5Vf;LiDUAL -DF/FIO2IC15IC12 -ICI 4C5-CISR.,S,vJJJ/v-+5VA15ADDR DSBLD0¢Do7DO DSBLS STACKSHLTASCUTSMIP SY NCROBINp WAITPWRPHLDAPINT ERDYHOLDINTRESETFig. 3. The logic associatedwith the CPU (ICI) is shownat left. All of the buffersand latches are on a singlepc board. Connecting wiringis through a 100 -line buss.decodes the instructions and sets upthe various registers, gates, etc., in theCPU for proper functioning. All systemtiming comes from the CPU. (The logicassociated with the CPU is shown inFig. 3, while the system clock is shownin Fig. 4.)Memory. A computer memorystores the various binary 0's and 1'sthat make up its language. These 0'sand 1's are known as bits. Somememories are organized to store 4, 16,24, or 32 bits to a word, whileothers -specifically those in the 8800computer -are organized to storeeight bits to a word. Each time the CPUrequests data from the memory, acomplete word is transmitted. Theterm byte is interchangeable with thePrinted circuit boards aredesigned so that the variousmating pads are aligned.Multi -conductor ribbon cableinterconnects the boards.term word in an 8 -bit processor. (Thebasic 8800 memory is shown in Fig 5.)The time required from when theaddress first appears until the data isstable is called "access time." In mostmodern semiconductor -memoryminicomputers, it ranges from 15 ns to30 µs. With proper adjustments, anymemory speed can be used in the 8800computer, although standard memorytime is 850 ns for a static random -access memory (RAM) and 420 ns for adynamic RAM. Higher -speed memorieswill not appreciably affectthe performance of the computer,while slower -speed memories will resultin an overall reduction in systemspeed.In addition to semiconductorRAM's, the processor will also serviceROM's (read -only- memories) andPROM's (programmable read -onlymemories). Access time should bereinforced for the particular memoryused.Any conventional memory can beused in the computer if the input loadingon the buss does not exceed 50TTL loads and if the buss is driven bystandard TTL loads. Normal expansionloads to the buss would be one+5V IC41P SYNC4)1PROTUNPROTIC47CIIR2R7+12V -C4R60Fig. 4. Computer operation is controlled bysignals from this 2 -MHz clock circuit.standard low -power load per expansioncard.Front Panel. The front -panel logicpermits the following functions:1. STOP: Stops the processor immediatelyafter it completes the cur-RDYIC48, 1049, IC38, IC41+5V1111-4WJvV--R9-R16RC3rent instruction. An automatic stopoccurs when power is turned on (interruptsare disabled).2. RuN: Starts the processor at thecurrent address.3. EXAMINE: Causes the data storedat the location (set by the switches) tov c-IC39, I043,IC40 IC44PROTECT STATUSM WRITEDO 95510A15MEMRIC37D'----D'IC45, IC46_-_E> ^ IIC40,IC41D07V 016R17-R24DIODI10I2DI 30I4DI5DI7+SVFig. 5. The basic memory contains up to eight 256 x 4 RAM's.36POPULAR ELECTRONICSIANUARY 197537

e displayed in binary by LED's.4. EXAMINE NEXT: Steps the Pcounter once and displays the wordstored at the next location.5. DEPOSIT: Causes the informationpreset by the switches to be stored inthe memory.6. DEPOSIT NEXT: Stops the Pcounter and loads the memory.7. SINGLE STEP: Steps the programone instruction.8. RESET: Clears the CPU and setsup a starting address of O.9. CLEAR EXT: Clears all input/ outputdevices; occurs automaticallywhen power is turned on.10. PROTECT /UNPROTECT: Allowsselective protection /unprotection ofblocks of memory. When a block ofmemory is protected, it is impossibleto write over that block, but its contentscan be read out.There are 36 LED status indicatorson the front panel, 16 of which areused for the address buss, 8 for thesystem status latches, and 8 for thedata buss. The four remaining LED'sare used for indicating memory -protect, interrupt, system -wait, andhold status.Power Supply. Four powersources are required to operate thecomputer: +5 volts at 2 amperes, 5volts at 500 mA, 12 volts at 500 mA,and +8 volts at 6 amperes. The firstthree are regulated, while the last isunregulated. Thethree regulated linespower the processor. The unregulatedline powers the peripheral cards thatcan be used to expand the system,each of which has its own 5 -volt regulatoron board. This reduces electricalnoise and obviates the possibilityof total system failure due to the failureof only one regulator.Expansion. The basic computer isdesigned for almost unlimitedperipheral and memory expansion,using a buss system where allinput /output connections merge intoa common line. Hence, an externalcard can be plugged into any slot andit will function properly. The only qualificationis that each card have an addressdecoder to allow the specificcard to take what data it needs fromthe common buss and put data on thebuss as required. The processor buffersare designed to drive 300 externalcards, which should be adequate formost applications. Bear in mind thatonly 17 cards will yield 65,000 words ofmemory.[Editor's Note: At this writing, anumber of different peripheral devices38are in various stages of design or undergoingtests]Assembly Details. The basic computeremploys four printed circuitboard assemblies, each of which containsone functional element of thebasic system. Because the boards arelarge and very complex, we are notpublishing etching and drilling guidesor component -placement diagrams.Instead, you can obtain a set of guides,diagrams, an instruction set, busspoints, and miscellaneous informationby sending a stamped self -addressed 81/2" x11" manila envelopewith 40c postage to MITS, Inc. (Seenote below Parts List for address.) Requestthe PE8800 package.The front panel display board accommodatesthe 36 LED indicatorsand their associated drivers. Addressline inputs AO through A16, data linesDO through D7, and the various statuslines originate on the CPU board. Theboards have been designed so that theSOME APPLICATIONS FOR THEALTAIR 8800 COMPUTERListed below is only a small sampling ofthe thousands of possible applicationsfor the computer. The Altair 8800 is sopowerful, in fact, that many of these applicationscan be performed simultaneously.It can be used as a:Programmable scientific calculatorMultichannel data acquisition systemAutomatic control for ham stationSophisticated intrusion alarm systemwith multiple combinationlocksAutomatic IC testerMachine controllerDigital clock with all time -zone conversionHigh -speed I/O device for largecomputerDigital signal generatorAutomated automobile test analyzerOn -board mobile controllerAutopilot for planes, boats, etc.Navigation computerTime -share computer system"Smart" computer terminalBrain for a robotPattern -recognition devicePrinted matter -to- Braille converterfor the blindAutomatic drafting machineAutomatic controller for heat, airconditioning, dehumidifyingController for sound systemsDigital filterSignal analyzervarious mating pads on both arealigned. Multi- conductor flexible ribboncable interconnects the boards.The front panel control board containsthe circuitry for the interfacingbetween the control switches locatedon the front panel and the CPU. In additionto the interconnections to theactual processor, this board acceptsmemory address switches AO throughA15 (also on the front panel). The firsteight of these switches (DO to D7) areused to put data into the CPU. TheEXAMINE /EXAMINE NEXT, DEPOSIT/DEPOSIT NEXT, SINGLE STEP, and RUN/STOP switches are also wired directlyto the front panel control board.The third board contains the Intel8080 central processing unit LSI chip,two -phase clock and buffers, and thevarious lines going to the buss. (Thebuffers are tri- state, high- inputimpedance,high- output -level devices.)This board also has four dual -Dflip -flops wired as latches for the eightbits of status information. All inputand output wiring to and from the CPUboard is via a 100 -line buss.The basic memory board contains256 eight -bit words of random accessmemory (RAM). It is directly expandableto 1000 words. This board alsocontains the input /output data -gating,address -decoding, memory -wait, andmemory -protect circuits. The memory-wait circuit allows the memorytime to stabilize the output data tothe processor, while the memory -protect circuit prevents accidentaloverwriting of the memory. All connectionsbetween the CPU and thememory board are via the 100 -linebuss.The four boards, along with thepower supply, mount in an 18 -in. deepby 17 -in. wide by 7 -in. high (45.7 x 43.2x 17.7 -cm) metal cabinet. The variousoperating switches and LED indi-cators go on the front panel. When allthis is done, the computer cabinet'sinterior will appear to be almostempty. However, the internal cablingsystem is arranged with connectors toaccommodate 17 more boards withinthe case, all connected to the mainbuss lines. The added boards can beused for memory, input /output devices,control devices, etc. All youhave to do is plug the boards into theconnectors and the computer doesthe rest.Part 2 of this article, next month, willdescribe the operation of the computerand present some sampleprograms.POPULAR ELECTRONICSTHE ELECTRONIC flash systembrought "stop action" photo opportunitiesto camera enthusiasts. Italso eliminated the need for changingspent flashbulbs thanks to the storageproperties of the electrolyticcapacitor and the use of long -lifegaseous lamps. The next major advancein e!ectronic flash technologycan be pinpointed to 1965 when HoneywellPhotographic introduced anautomatic electronic flash, freeingphotobuffs from having to set f -stopsfor each shot that was at a differentdistance.Now electronics has createdanother plateau in automatic flashtechnology by adding thyristorcontrol -an SCR that both triggersthe flash and stops capacitor dischargewhen the subject receives sufficientlight. The result? More flashesper battery charge, faster recyclingtime for the next shot, and short rechargetime.A Flash of Light. For background,here are the various steps that go intoproducing the electronic flash oflight. First, voltage from a battery, theusual power source in an electronicflash, is converted to ac by means ofan oscillator circuit. (This oscillator,by the way, is what causes the characteristic"whine" you hear in the electronicflash unit.) Once the ac is generated,it is stepped up to a highervoltage by a transformer. Then the acis converted back to dc by a rectifier,after which it is stored in the flashunit's main electrolytic capacitor.(Capacitors in modern flash units arecapable of storing potentials of about350 volts.) The flash capacitor is connectedto a gas -filled tube. Xenon isthe usual gas used, although someother types are available.111GBY MICHELE FRANKodit Ñc0r.á herspft°How asimple SCR triggerprovides faster recycling,more flashes per chargeand quick rechargefor the latest breed ofautomatic electronicflashers39

VOLTAGESUPPLYVOLTAGESUPPLYVOLTAGESUPPLYMAIN FLASHCAPACITORMAIN FLASHCAPACITORSWITCH;MAIN FLASHCAPACITORAt this stage, everything is set fortriggering the flash. What is nowneeded is a high -voltage pulse toionize the gas in the flashtube tomake it conductive so that energy canflow through the tube, where it will beconverted to light. This high -voltagepulse is created as the camera's shuttercontacts close, causing a smalltrigger capacitor to release its chargeinto a spark coil connected to the wallof the flashtube. After the charge onthe flash capacitor has been exhausted,the gas becomes de- ionizedand no longer conductive. The rechargingcycle can then begin. Oncethe cycle is complete, as indicated bythe ready lamp on the flash unit, theflash can again be fired.Automatic Flash. Film exposure isbased on two factors: time and intensity.With the pre -1965 photoflashers,the time factor (flash duration) wasfixed at about 1/1000 of a second formost units. Hence, intensity had to becontrolled by changing the camera'slens opening (f- stop).The Honeywell 660 automatic flashemployed the first "quench circuit"and operated on the variable of time.Now, instead of just one flash ,durationof perhaps 1/1000 second, theflash unit would give a burst of lightwith a duration of anywhere between,40(A)CONTROLCIRCUIT(e)CIRCUIT(CROL(C)FLASH LAMP100908070605040302 010Three greatly simplified blockdiagrams show the major componentsof the various types ofelectronic flashers. At (A),a manual unit is the leastcomplex. Diagram (B) shows howa photocell is added with controlcircuit and quench tube todump surplus energy. At (C),a thyristor unit adds an SCRto trap voltage from the mainflash capacitor.ENERGYWASTEDENERGYSAVEDENERGY ENERGY ENERGYUSED USED USEDA 8Energy used by three electronic flash units shootingthe same scene. At (A), the manual unit usesall the voltage stored in flash capacitor toilluminate the scene. Proper exposure is obtainedby setting the f -stop on the camera. In unit (B),a quench -tube type, exposure was controlled by theflash unit. Only 45 percent of the energy was usedto expose the film. Flash unit (C) used the sameamount of time and energy as (B) to illuminate thesubject properly but unused energy remained in theflash capacitor, resulting in less battery drainas well as a faster recycling time between shots..POPULAR ELECTRONICSTRACES FROM AN ENERGY -SAVING FLASH UNIT1111111111IiimitinIl IMINEMOImAlmonownimOscilloscope traces show resultsof synthesizing various workingdistances by regulating a set ofbaffles in front of a Braun 2000flash unit, then measuring theresulting flash waveform with aphotomultiplier and scope set to0.2 ms per division. Effectiveflash duration varies frommaximum of 1 11000 s (equivalentto using unit on manual or atits maximum working distance) tominimum of 1 /32,000 s (using unitat closest working distance).Peak in the waveform on middlefour traces is from firing ofthe flash tube. This is acharacteristic of some, but notall, of latest energy- savingflash units using thyristors.JANUARY 1975MERINIMEMINIIIIIIIMIiI NMI 1111111111111111MMN IMMUNEEMI. t1 ,. .1/32,000 sec. 10 microsec.1.4-MMIIINI\'ENWe used a high -speed oscilloscopeto check flash duration of theBraun 2000, set to give briefestflash of 1 /32,000 s. Measurementfrom pulse width at half height.1/1000 and 1/30,000 second. The exposurecontrol was taken from thecamera, and the photographer put inthe flash unit. The photographer hadonly to set an f -stop on his camera,following the recommendations ofthe manufacturer based on the lightintensity from the flash unit and theASA of the film. The flash unit wouldthen control the duration of the light.Here's how it works. Light emanatingfrom the flash tube is reflectedfrom the subject back to the flashunit, where it is detected by a photocell.The photocell is connected to asmall timing capacitor whose valuehas been carefully selected based onknown criteria (f-stop to be used witha given ASA of film, light intensity,and distance) that add up to an exposureanalog. The amount of lightfalling on the photocell can be biasedeither by using small apertures orneutral- density filters placed beforeit. By so doing, the photocell can befooled into believing that it takes two,three, or four times as long to illuminatethe scene. Responding to theamount of light falling on it, thephotocell regulates the charging ofthe timing capacitor. Once the timingcapacitor has reached its full chargein a quench -tube circuit, it closesanother switch that allows the currentflowing from the flash capacitor to beshunted to another tube, with a lowerseries resistance. Here, the energy isexpended in the form of light andheat.This second tube is never seen bythe photographer, and its light neverplays a part in the photographic process.It is just a convenient way ofdumping the unneeded energy flowingfrom the flash capacitor. With thisapproach, flash durations of up to1/70,000 second have been obtainedwith small electronic flash units, permittingus to record such things asbullets piercing wood, balloonsbreaking, etc.All of this was enough to send mostphotographers into fits of ecstasy, butit still left one problem. Even thoughthe quench -tube idea broughtenormous flexibility to electronicflash units, they were still energy wasters.There was no feasible way todam up the energy flowing from theflash capacitor to the flash tube. Theresult was that a photographer couldobtain only a limited number offlashes per battery or charge. In thecase of the rechargeable nickel-41

cadmium battery, this was usually supply the small amount of energyabout 40 to 60 flashes.necessary to recharge the capacitor.Battery power can be conservedEnter Thyristor Control. In the fall -meaning more flashes per charge.of 1972, Braun introduced the first One series -type thyristor flash unitseries -circuit, thyristor- controlled known to us recycles in about 2.5flash units. The much -sought-after seconds after illuminating a scene 10breakthrough came in the form of a ft (3.05 m) away. In doing so, it usessmall silicon controlled rectifier only 22 percent of the energy in the(SCR) called a " thyristor." Operating flash capacitor. However, if this sameas an electronic switch, this little unit is fired at a subject 20 ft (6.1 m)solid -state wonder can handle the away, it will have used up 90 percentload flowing from the flash capacitor of the stored energy and will require 6and stop it at the precise moment that seconds to recharge. At distances ofthe exposure control circuit says the 2.5 ft (0.76 m), the recycling timesubject has received enough light. In- would be only about 0.25 to 0.33 sec -stead of having a parallel circuit that ond. In the manual mode (with thesimply reroutes the energy from the photocell covered), or at distances atflash capacitor, we now have a series the very end of the electronic flash'scircuit that allows the leftover energy ability to properly illuminate theto remain in the flash capacitor. scene, the thyristor does not receiveThe thyristor has many advantages, the reversing pulse from the timingamong them: It can switch on and circuit. Instead, it opens after the volremainon until the current flowing tage in the flash capacitor has drop -through a dc circuit drops to zero (or ped to near zero (usually about 1.5near zero). It can be made to open if it volts).receives a very brief low- energy pulse Battery conservation goes hand infrom the opposite direction. The hand with the storage of energy in thepulse to shut down, of course, comes flash capacitor. Before the thyristorfrom the timing circuit with its small made its appearance in flash units, itcapacitor connected to the photocell. was necessary each time to supplyUsed in an electronic flash unit, the enough power to bring a fully dethyristorperforms two jobs. First, it pleted capacitor up to full charge.stops the current flowing from the Now, the thyristor has reduced themain flash capacitor, thus regulating requirement so that only fractions ofthe duration of the flash in the same the earlier power are required to remannerthe parallel quench circuit charge a partially dischargeddid. And it allows the unused energy capacitor. In some cases, if the flashto remain in the flash capacitor, unit is used exclusively at the closestrather than being wasted. This, in working distances 1where the duraturn,provides another advantage. tion of the flash is briefest), it is notRecycling times can be shortened uncommon to obtain 700 to 1000because the battery can very quickly flashes per nickel- cadmium battery42charge. (On manual, these same batterieswould deliver only about 60flashes per charge. Since no oneshoots exclusively at distances of 2.5ft (0.76 m), the more usual number offlashes per charge is about 100 to200.Thyristor- controlled electronicflashes are not likely to glut the marketin the near future. This type offlash makes sense only with the morehigh -powered flash units. The low -powered flash units generally requirethe entire flash charge on thecapacitor to illuminate scenes greaterthan 10 ft (3.05 m) away; so, therewould be no energy savings by buildinginto them a thyristor circuit. Onlyflash units where a small amount ofenergy would be used in a shot wouldmake the thyristor circuit practicaland necessary.Another thing barring the universaluse of the thyristor in electronicphotoflash units is that this type ofSCR is expensive and can be tricky tomake. Quality control must be verytight, which reduces the number ofdevices available. This means thatthyristor suppliers are having a roughtime trying to keep up with the demand.Manufacturers tell us that theyare having troubles trying to getenough thyristors just to meet thedemand for flash units now in production.When you do see a thyristorcontrolledflash unit, you can bet youwill have to pay more for it than youare accustomed to do for "conventional"flash units. The type of sophisticationbuilt into these flash unitsdoes not come cheap. Perhaps whensemiconductor manufacturers cancrank out this type of SCR the wayother manufacturers crank out resis-tors, a price reduction can beanticipated -but not before then.Who Makes Them. If you want tolook for one of the new thyristorcontrolledflash units, ask for any ofthe following in your local photostore: Argus Model 1272 or Model1275; Auto Spiralite Thy 1000; Bell &Howell Model 880; Braun Vario Computer2000 F022 or F027; HoneywellAuto Strobonar 470; Metz Mecablitz402 or 217; Rollei Model 36 RE orModel 140 RES; or the Vivtar AutoThyristor Model 292 or Model 352.Canon, Minolta, and Nikon also marketthis type of electronic photo flashunit outside the U.S.POPULAR ELECTRONICSAstate -of -the -artreporton charge- coupleddevicesand scannedphotodiodearrays.BY HARRY GARLANAND ROGER MELEiAN EXPERIMENTAL TV camerahas been developed that is nolarger than a pack of cigarettes.Equipment is being installed atsupermarket checkout counters thatcan automatically read price tags.There is even a machine that enablesblind people to read ordinary printedmaterial. All of these developmentsare made possible by the use of solid -state image sensors -a special type ofintegrated circuit.An image sensor can contain hundreds,even thousands, of individualphotosensitive elements on a singlechip of silicon. It is normally mountedin a standard IC package that is coveredwith a transparent top. When ascene strikes the image sensor, usuallythrough a lens as shown in Fig. 1,the individual elements of the sensorcan be scanned electronically andtheir outputs displayed.Area vs. Image Array. The photosensitiveelements of an image sensorcan be in either a linear or an areaarray. In a linear array the elements arein a single line; in an area array, theyare in a two -dimensional matrix.JANUARY 1975CRT DISPLAYSolid -StateImageSensorsTV CameraliebeSuccessor?SCANCIRCUITRYIC IMAGE SENSORFig. 1. An image- sensor system.A linear array can be used to producea two -dimensional picture, butonly one line at a time as the image512 26'G E4moves across the sensor. The numberof elements in an array determines theresolution of the picture. The effect ofresolution on picture quality is shownin Fig. 2. Here, the same picture isscanned by five different linear arrays.The array with the lowest resolution(32 elements) produced the picture atthe right, while the picture on the leftwas produced by an array with 512Fig. 2. Photos of displays show how resolution affects picturequality. Number of elements in array increases from right to left.43

elements. The improvement in qualityfrom right to left is obvious.The advantage of an area array overa linear array is that the image doesn'thave to be scanned from top to bottomto produce a two -dimensional pictureAn example of an imaging systemusing a lens to image a picture onto a2500 -element area array is shown inFig. 3. The sensor is electronicallyscanned and its video output is displayedon a CRT. The array used is aReticon Model RA50X50 (Fig. 4).The reading aid shown in Fig. 5 wasdeveloped at Stanford University andhas a 144 -element (6 X 24) image sen-Fig. 3. Solid -stateimaging systemusing a 50 by 50sensor array. Theimage can be seenon CRT in front.Fig. 4. Close -upof the ReticonRA 50 x50 sensor.The background isphoto of the arraymagnified many times.Fig. 5. Reading aid for blind is used by scanning letters with sensorin right hand and feeling them with left hand on tactile display.44sor. A small camera containing theimage sensor is used to scan a printedpage. The outputs of the sensor controla 144- element tactile display that ablind person can feel by fingertip. Thisreading aid, known as the Optacon(Optical to Tactile Converter) is beingproduced by Telesensory Systems Inc.SILICON(A) (9)Fig. 6 With normal light on pieceof silicon (A), resistance is high.More light lowers resistance (B).Types of Image Sensors. Integratedcircuit image sensors can bebuilt in a number of different ways.The two most common types are thecharge -coupled device (CCD) and theMOS scanned photodiode array. Bothtypes make use of the inherent lightsensitivity of silicon.The light sensitivity of silicon can beobserved by performing the simpleexperiment shown in Fig. 6. When astrong light is shining on the silicondevice, the resistance of thesilicon is seen to decrease. What isbeing observed is the process ofphotogeneration. When light interactswith silicon, current carriers (bothholes and electrons) are generated,reducing the resistance. In fact, eachphoton that interacts produces onehole and one electron (sometimescalled a hole -electron pair).Silicon is not uniformly sensitive toall wavelengths of light. In fact, siliconimage sensors are generally muchmore sensitive to red light and the0.200 0.400 0.600 0.800 1.000WAVELENGTH (MICRONS)Fig. 7 Spectral response ofsilicon to various colors of light.1.200POPULAR ELECTRONICS14) iCLOCKINPUTCHARGEFig. 9. Photodiodearray is scanned byswitching sequentiallyfrom one to another7VIDEO OUTPUTnear infrared than they are to shorter-wavelength blue light. The sensitivityof an image sensor to differentcolors is summarized in the spectralresponse curve shown in Fig. 7.CCD Arrays. Charge -coupled deviceimage sensors enjoy one major advantageover MOS scanned photodiodearrays: they can be built more denselyand with larger' numbers of elements.The basic photosensitive element in aCCD is an MOS capacitor. An entirearray of these capacitors makes up theCCD image sensor. The key feature ofthe CCD is that charges can be transferredsideways, from one MOScapacitor to another.The operation of the CCD imagesensor is shown diagrammatically inFig. 8. Fach of the capacitors can beJANUARY 1975+5VIDEOOUTPUTFig. 8. Charges in CCDarray are transferredfrom left to right toproduce a video output.4-5Fig. 10. Self -scannedphotodiode array isscanned by transistorson the IC chip.VIDEOOUTPUT/fconsidered as a small "bucket" thatholds a charge. When light shines onthe sensor, a charge is produced in thebucket through photogeneration. Themore light that shines on a particularbucket, the more charge produced.The video information is read out byquickly transferring the charge fromone bucket to the other and measuringthe charge at the output. All of thecharges are emptied from the bucketsin this process and the cycle can thenbe repeated.The image sensor with the largestarray that is commercially availabletoday is a 100 X 100 (10,000 -element)CCD array produced by FairchildSemiconductor. This image sensorproduces excellent pictures, but fallsshort of providing full television resolution.Before that can be achievedwith an IC, a 512 X 320 (163,840 -element) image sensor must be developed.This would be a very largesensor indeed, and its developmentpresents a real challenge to the electronicsindustry. RCA has recentlyannounced an experimental CCD thatcomes close to providing this resolution,but it is not being producedcommercially at this time.Scanned Photodiode Arrays. Inthe MOS photodiode image sensor,the photosensitive element is a silicondiode. When reverse -biased and in thedark, a very small leakage currentflows through a photodiode. This iscalled "dark current." When lightshines on the diode, current carriersare generated and more current flows;and the current increases as the lightintensity is increased.The operation of a scanned photo -diode array is shown in Fig. 9. The fourdiodes are sequentially scanned by arotating switch. Notice that a smallcapacitor is shown across each diode.The capacitors are not separate corn -ponents; they represent the inherentcapacitances of the diodes. When adiode is selected by the switch, its inherentcapacitor charges up throughthe resistor to the level of the 5 -voltsupply. As the switch moves on toanother diode, the first capacitor dischargesthrough its photodiode. If nolight is hitting the diode, the small darkcurrent will only partially dischargethe capacitor. With more light on thediode, the capacitor is more fully dischargedby the higher current. Now,when that diode is again selected bythe switch, an output signal is producedas the capacitor recharges to 5volts. This video output signal iscaused by the voltage drop across theresistor. The more the capacitor isdischarged, the greater will be thevideo signal. Image sensors that operatein this manner are operating in thecharge- storage mode.Scanned photodiode sensors useMOS transistors as switches to scanthe diode array. The photodiodes areactually the source -to- substratediodes of the MOS transistors. Asshown in Fig. 10, the MOS transistorsare sequentially "closed" by pulsesfrom a shift register which is indexedby a clock input. Image sensors thatinclude shift register circuitry right onthe IC are said to be self- scanned. TheReticon image sensor mentioned earlieris an example of a self- scannedMOS photodiode array.45

IF YOU ARE READY FOR SERIOUS CAREENLearn Co ege -LevelADVANCEMENT NOWElectronics at H onceWith CREI's unique ElectronicDesign Laboratory ProgramThere is only one way to a career inadvanced electronics- through advancedtraining. You can get such training througha resident engineering college or you can takea CREI specialized college level electronicsprogram at home.Wide Choice of Programs, CREI offers youprogram arrangements with fourteen areas ofspecialization in advanced electronics. Youcan select exactly the area of specializationfor the career you want.CREI also offers program arrangementsboth for those with extensive experience inelectronics and for those with only limitedexperience. All programs are college -level,except for a brief introductory level course,which is optional.Unique Laboratory Program. CREI now offersa unique Electronic Design Laboratory Programto train you in the actual design of electroniccircuits. You also get extensive experience intests and measurements, breadboarding, prototypebuilding and in other areas importantto your career. The Lab Program makes iteasier for you to understand the principles ofadvanced electronics. Only CREI offers thiscomplete college type laboratory program.The Lab Program includes professionalequipment which becomes yours to keep.You will especially appreciate the ElectronicCircuit Designer, which is available onlythrough this program and which you will findextremely valuable throughout your professionalcareer.College Credit. You can actually earn collegecredit through CREI programs, which you canuse at recognized colleges for an engineeringdegree. CREI maintains specific credit transferarrangements with selected colleges in the U. S.Industry Recognized Training. For nearly50 years CREI programs have been recognizedthroughout the field of electronics. CREIstudents and graduates hold responsiblepositions in every area of electronics and areemployed by more than 1,700 leading organizationsin industry and government.Qualifications to Enroll. To qualify for enrollment,you should be employed in electronicsor have previous experience or practical trainingin the use of electronic equipment. Youmust also be a high school graduate or trueequivalent.All CREI Programs are availableunder the G.I. BillSend for FREE Book. If you are qualified,send for CREI's full color catalog describingthese college -level programs and your careeropportunities in advanced electronics. Mailcard or write for your copy of this book.CAPITOLRADIOENGINEERINGINSTITUTEMcGraw -Hill Continuing Education Center3939 Wisconsin Avenue NorthwestWashington, D. C. 20016Accredited Member, National Home Study Council49

50ANIGNITION TIMING LIGHTFORIMPROVING GAS ECONOMYNOWADAYS, everyone knows howimportant it is to get the best gaseconomy possible from an automobile.One of the more importantfactors that affect economy is enginetiming. In addition, proper timing isrequired on all automobile engines sothat exhaust emissions do not exceedallowable limits.Timing changes for a variety ofreasons. As the parts of an enginewear, the timing tends to become retarded.If ignition points are replaced,timing is also disturbed. Furthermore,it is virtually impossible to set the pointgap exactly the same as it was whenthe timing was last set.Using a dwell meter is a far moreaccurate method of setting point gapthan using a feeler gauge, but eventhis will not guarantee proper ignitiontiming. The fact is, the best way tocheck ignition timing is with a timinglight.The timing light described here canbe built for only a few dollars. Yet, it isdesigned to perform as well as acommercial unit costing $25 or more.Its light output is bright enough to useBY ANTHONY CARISTIunder conditions of bright daylight,and it is battery -powered (from thecar's battery)to make it independentof the ac line.About the Circuit. The heart of thetiming light's circuit (Fig.1) is dc-to-dcconverter transformer TI. It alternatelyswitches current between transistorsQ1 and Q2, while stepping up the batterypotential to about 125 volts. A ferritepot core was chosen for this circuitto keep down project size andcost.The primary winding of Tl (woundaround the pot core) is done by the"bifilar" method that gives tight couplingand accurately locates thecenter tap. The tight coupling is essentialto keeping the voltage spikesacross the transistors to an absoluteminimum. (In this type of circuit, thespikes can easily exceed ten times thesupply voltage if a poorly designedtransformer is used causing transistorfailure.) By using a bifilar winding forthe primary, the voltage spikes acrossQ1 and Q2 are well below the 60 -voltrating of the transistors.CONSTRUCTIONThe stepped -up voltage from thesecondary of T1 is again stepped up bythe voltage -doubler circuit consistingof D1 and D2. It is then passed intoflashtube FT1.Construction. Perhaps the mostdemanding part of the constructionprocess is the winding of T1. Even so,the job is not difficult, only time -consuming. The transformer shouldbe wound in the following manner:Start by winding the feedback loop(its leads are labelled through 3 in1Fig. 1) on the bobbin supplied with theferrite core. Use No. 30 enameled wire.This winding consists of 10 turns ofwire, interrupted at the 5th turn for acenter -tap connection. Connect andsolder 5 -in. (12.7 -cm) lengths ofstranded hookup wire to the ends andcenter -tap of the winding. Label theleads at the first turn, 2 at the center -1tap, and 3 at the final turn. Then wrapthe winding with a layer of thin Mylaror plastic tape.Next comes the bifilar -wound primarywinding This consists of 27.double turns of No. 30 enameled wire.POPULAR ELECTRONICSà';ARBATTERY2N5296RI6811 2= aCI.005pF5Ìó022N529602-22pFPARTS LISTCI- 0.005 -4, 500-volt disc capacitorC2- 22 -µf, 25 -volt tantalum electrolyticcapacitorC3,C4- 20-µf,150 -volt electrolyticcapacitorD1,D2- 500 -volt, 1- ampere silicon rectifier(1N2070, HEP R0053 or equivalentFTI- 250 -volt, 50 -watt- second flash -tube(Radio Shack No. 272 -1145 or similar)Q1,Q2 -60 -volt, 1- ampere npn silicontransistor (2N5296 or equivalent)RI-68 -ohm, 1 -watt resistorR2- 560 -ohm, 1 -watt resistorR3- 470 -ohm, 2 -watt resistorR4- 220,000 -ohm, 1 -watt resistorT1 Transformer wound on TDK TypeIiDI1N2069H5A P2213 Z52H ferrite core and TDKType BP 2213 -612 bobbin (See text)*Misc. - Flashlight body (see text); color -coded test lead cables; alligator orcrocodile clips with insulated boots (2);rubber grommet; printed circuit board;Dow Corning Silastic® cement;machine hardware; stranded hookupwire; No. 30 and No. 36 enameled wire;spring -type spark plug cable connector(available from most automotive supplyoutlets); stranded hookup wire; solder;etc.The TDK ferrite -core/bobbin assembly isavailable for $3 from: Anthony Caristi,69 White Pond Rd., Waldwick, NJ07473.Fig. 1. The dc -to -dc converter (TI) steps up the battery voltage.Label one end of a 4 -ft (1.22 -m) strandof the enameled wire with a 4. Labelone end of a similar strand 5. Startingwith these two ends together, wind 27turns of both wires on the bobbin.Using an ohmmeter, determine theunmarked end of the wire that startedwith 4 and connect it to the endTI TI BATT6 +)T31JANUARY 1975- R3 +BATT( ---DI- K-D2--)marked 5. This is the center tap. Theother unmarked end is terminal 6.Cover the winding with tape to hold itin place and insulate it from the secondary.The secondary winding consists of240 turns of No. 36 enameled wire.This is the most tedious part of as--R4-FTI(-)C3C44FTI(+)Fig. 2. Foilpattern is above,componentplacement, left.sembly. Be sure to accurately countthe number of turns as you go. Howmany turns you wind will determinethe dc potential applied to the flash -tube. When you are finished winding,attach 5 -in. lengths of strandedhookup wire to the winding ends andlabel them 7 and 8. Then wrap theturns with tape.Now you can begin assembling thecircuit proper. A printed circuit boardis recommended for componentmounting (see Fig. 2 for actual -sizeetching and drilling guide and componentsplacement diagram).Transformer Ti is mounted on theboard with the aid of a 6 -32 x 1 -in.machine screw, fiber washer, (at thetop of the transformer), and a 6 -32 nut.Do not overtighten the hardwareor you will crack the core, renderingit useless. (Note: Capacitor C4mounts on the board atop C3 as shownin Fig. 3)When the circuit board assembly iscompletely wired, temporarily connectto the appropriate points on it redand black hookup wires for the positiveand negative battery leads. Connectthe leads, properly polarized, to a12 -volt battery or other dc source. Ifthe board and transformer are properlyassembled, you should hear ahigh -pitched tone when power is applied.This is the vibration of the transformercore as the circuit oscillates. AVOM connected across R4 shouldprovide a 250 -volt reading if the inputpotential to the circuit is set to 14.5volts. If the circuit does not oscillate,the phasing of the feedback windingof T1, may be incorrect, in which case,you can transpose leads 1 and 3 andtry again. Remove the temporaryleads.The type of flashlight body bestsuited for your timing light is shown inthe lead photo. You will have to drilltwo mounting holes for the circuitboard assembly. A third hole that permitscolor -coded battery and plugleads to exit the flashlight body shouldbe lined with a rubber grommet. Passthe leads through this hole and connectand solder them to the appropriatepoints on the board. Terminatethe positive and negative battery leadswith insulation -booted alligator orcrocodile clips and the plug lead witha spring -type plug -to -cable adapter.Turn over the circuit board andcarefully solder a 4 -40 machine nut tothe copper pads surrounding themounting holes. Make certain that thenuts are centered over the holes andthat no solder flows into the threads.51

52The flashtube mounts in theflashlight's reflector. You can enlargethe standard lamp hole in the reflectorwith a rat -tail file, working carefully toavoid damaging the reflector orscratching its reflective coating. Theflashtube's fit should be reasonablyclose without binding. Place the reflectorassembly face down on a flatsurface and insert the flashtube in theenlarged hole, positioning it with itspoint against the glass lens and verticalto the plane of the lens. Run a beadof epoxy or Dow Corning Silastic"'cement between flashtube and reflectorand allow the cement to set overnight.Be sure to maintain the flashtubevertical to the lens as the cementsets (Fig. 4).Once the cement has set, you cancomplete final assembly. Locate thenegative (woven) electrode lead of theflashtube and connect it to the holemarked FT1( -) in the component -placement guide in Fig. 2. Then connectthe positive electrode lead (it exitsthe end of the flashtube oppositenegative electrode lead) to theFT1( +) point on the board. The onlyconnection left to be made is thespark -plug test lead. Locate this leadand connect and solder it to the high -voltage terminal on the flashtube.(Note: The high- voltage terminal is themetal band affixed to the outside ofthe flashtube.) Pack the connectionwith Silastic cement to insulate it andset the assembly aside to harden.When the cement has set, slide thecircuit board assembly into the flashlightcase and anchor it in place withFig. 3. Wired pc board assembly shows TI mounted withhardware fiber washer. C4 is on top of C3.two 4 -40 x 1/2-in. machine screws. nearest the front of the engine. TheScrew on the reflector assembly but number -one cylinder on a V8 engine isunder no circumstances permit the re- also nearest the front, but it could beflector itself to rotate. If you allow the either on the left or the right.) With thereflector to rotate, the flashtube will be engine shut off, remove the ignitiondamaged or a short circuit will de- leadnnnect the timing nrlight's plug lead toReplace the ignition wire.How to Use. Before making any tim- the plug. ping adjustment on your car, set the Before starting the engine, it is addwelltime of the ignition points ac- visable to clean the flywheel and paintcording to the recommendation of the a thin white line over the timing markmanufacturer of your car. This can be so that it is readily visible. Then refer toaccomplished by using a dwell meter the decal, located in the front of theon most General Motors cars and ad- engine compartment of late modeljusting the points with an Allen cars, to determine the calibration ofwrench while the engine is running. the timing scale and proper ignitionOn other car makes, the dwell angle timing specifications.must be set by adjusting the point gap Remove the rubber hose connectedopening. Bear in mind that the dwell to the vacuum diaphragmplug sof the dngangle must always be properly set tributor and p gbefore the timing is adjusted as with a pencil. This disables the auchangesin the dwell angle will change tomatic vacuum advance built into thedistributor. Timing of an engine is alignitiontiming.Locate the number one cylinder of ways adjusted with the vacuum adyourcar's engine. (On 4- and vance disabled. If you neglect to do6-cylinder engines, it will be the oneand the engine will not operate prop-Fig. 4. Flashtube mounts in enlarged hole in light reflector.erly.Connect the remaining two timinglight cables to the car's battery, observingthe proper polarity. Start theengine. The light should now be flashingat a rate of 4 to 5 times per second.Aim the timing light at the flywheel tolocate the timing mark. The markshould appear to be stationary. If timingis not correct, loosen the bolt thatclamps the distributor assembly to theengine and rotate the distributor in thedirection that yields the proper indication.Tighten the bolt and recheck thetiming to make sure it has notchanged.Stop the engine. Remove the timinglight and replace the hose to thedistributor's vacuum -advance diaphragm.The timing of the engine isnow correctly set. It need not bechecked again until the points are replaced.POPULAR ELECTRONICSIAn Under$UTHE inexpensive four -functioncalculator is an eminentlypractical tool for everydayhome and primary -school use; however,high -school students, engineeringand science majors in college, andpracticing engineers and scientistsrequire more sophisticated equipment.Fortunately, there is a newbreed of calculators that is rapidlygaining popularity in professional andadvanced -student circles. Going bysuch names as "scientific" and"slide- rule" calculators, they expandby several magnitudes the number offunctions and the information -handling capacities of "ordinary" calculatorsfor limited uses.JANUARY 1975Ten digits of mantissa with 2 -digit exponent and a full range ofscientific operations, including double -nested parentheses.Scientific calculators may be capableof obtaining nth roots and nthpowers; trigonometric functions(sine, cosine, tangent, etc.); naturaland common logarithms; degrees -toradiansconversions; and many otherfunctions. As a general rule, these calculatorsalso feature at least one levelof store /retrieve memory, a 10 -digitmantissa with two -digit exponent, andseparate displays to indicate negativequantities (in both mantissa and exponent)and overflow and disallowedfunctions.Most scientific calculators with thecapabilities described above sell for$150 or more at this writing. But thePOPULAR ELECTRONICS full -function,200 -decade scientific calculator costsonly $89.95 in kit form. It is 33/e" wide, 6"long, and 11/2" thick.What It Does. What can you, as anelectronics experimenter, do withsuch a calculator? The answer is, justabout anything you want to do in problemsolving. For example, supposeyou wanted to know the equivalent resistanceof a network of three resistors(560 ohms, 390 ohms, and 670 ohms)in parallel. By hand, this problemmight take you 10 minutes or more.With the calculator, less than 30 secondsis needed to get the answer(171.1638788.).Approaching a more difficult prob-53

54>+mómUHMmrn sr-UHOoNoóNmNaiIaO N Aónn Nv nNar mNnaNcr.HNVHo moio O NM Q N N0 0 0 O O 0 Om CO 0-N NFig. 1. IC1 and 1C2 are special MOSIC's that accept the keyboard commands,perform the required operations,and deliver a signal for the 14 -digitLED display. The other IC's formthe interface between the MOS and LED's.The two -way transistor power supply generatesthe negative voltage needed by IC1 and 1C2.UZNM NInóm-p NNTVn wwvN_á°zoHr --r01515-015u3puus-NI:LLUr ar-+ÑNácá_POPULAR ELECTRONICSPARTS LISTBI,B2 -3.5 -volt rechargeable batteriesCI- 50-VF, 6 -volt electrolytic capacitorC2,C3- 4.7 -VF, 10 -volt electrolyticcapacitorD1 to D3- 1N4148 diodeD4- 1N4001 rectifier diodeD5- 1N4739 zener diodeDIS1 -14 -digit light- emitting diode scientificdisplayICl,IC2 -MOS scientific calculator integratedcircuits (see note)IC3 to IC5- SN75492 hex inverter integratedcircuit (Texas Instruments)IC6,IC7- SN75491 7- segment driver integratedcircuit (Texas Instruments)Jl- Subminiature phone jackQI to Q3- 2N5232 transistorRI-Optional charging resistor (value contingenton charging current desired)R2- 2.2- megohm, 1/4 -watt resistorR3- 22,000 -ohm miniature printed circuitpotentiometerR4- 3900 -ohm, 1/4-watt resistor'R5- 1500 -ohm, V44 -watt resistorR6-4.7-ohm, -watt resistorR7 to R14- 220 -ohm,'/4-watt resistorTl- Special converter transformerMisc. -Calculator case; keyboard assembly;recharger; mounting nuts (2); thininsulating washer; Molex Soldercon eprinted circuit connectors; fine solder;etc.Note: The following are available fromNetwork Research Corp., 27 Eagle St.,Spring Valley, NY 10977: complete kit ofparts including manual, batteries, and acadapter /recharger for $89.95 (New Yorkresidents add sales tax); #N1003keyboard assembly for $12.00; #N1002display assembly for $19.50; #N1001etched and drilled pc board for $5.50;#N1000 MOS scientific calculator IC'sfor $60 the set; #N1005 transformer for$3; #N1004 interface IC's (5) for $9.50the set.lem, suppose you wanted to know theequivalent impedance of a 560 -ohmresistor and a 25.5 -mH choke at 2500Hz. The solution, 687.5569736, takesabout a minute with the calculator,considerably more time with paperand pencil.To give you a better idea of howpractical the calculator is, you canthrow away your logarithm and trigonometrytables. You won't need themagain because they are only a fewkeystrokes away in your calculator-all figured out to an accuracy of ninedecimal places. And that goes for n aswell. (A more detailed list of thecapabilities of this calculator is givenin the box.)JANUARY 1975The POPULAR ELECTRONICS calculatorhas built into it two levels ofnested parentheses, each of which definesa variable before executing afunction command. This permits theproblem to be "written" into the calculatorexactly as it is written down onpaper. When a new parentheticalstatement is opened, the previous resultsand functions are stored in thecalculator until that level of parenthesesis closed later in the problem.So, a complex problem likex = sin1 31 +v' (a +b)2 (c +d)2where a = 4, b = 5, c = 2, and d = 3 canbe solved quickly with the aid of theparentheses. The keystroke sequencewould be: 1, +, (, (, 4, +, 5, ), x2, , (,2,+, 3, ), x2, ), \, =, 1 /x, sin, xY, 3, =.When the last keystroke is executed,the display will read the answer,8.70831579 09, which means that themantissa is the number shown raisedto the negative ninth power of 10(10-9), which means further that thecalculator employed another built -infeature -automatic scientific notation.(The calculator goes automaticallyto scientific notation wheneverthe solution is an excessively large oran excessively small number.)Note that in the above sample problemno memory or external scratch -pad was required to find the solution.About the Circuit. The schematicdiagram of the complete scientificcalculator is shown in Fig. 1. SpecialMOS integrated circuits IC1 and /C2are the heart of the circuit. They acceptkeyboard entries, perform allmathematical operations demanded,and deliver a multiplexed output to thedriver circuitry for the 14 -digit LEDdisplay. (The display consists of 10mantissa digits, two exponent digits,one negative -sign digit for the exponent,and a final digit that combinesthe disallowed- function, minus -sign,and radian -function notation to theleft of the mantissa.)Buffers /C3 through /C5 drive the 14digit -enable lines, while /C6 and /C7are the segment drivers for the display.Note that all similar segments aredriven simultaneously, with the digitselector choosing the correct digit ofthe moment.Because the MOS chips requireboth positive and negative 7 volts dcreferenced to common to operate andonly a 7 -volt battery is used in the cal -cul ^tor, a two- transistor (Q1 /Q2) dcto-dcvoltage converter is required. Inconjunction with Ti, R4, and C2, theQ1 /Q2 circuit forms a push -pull poweroscillator. The output of Ti is rectifiedby Dl and D2. It is then filtered by C3 todeliver the 7 volts required. TransistorQ3 is the power -saver switchingregulator, while potentiometer R3permits adjustment of the battery'slow- voltage cutoff point.Rectifier diode D4 converts the acfrom the plug -in charger to pulsatingdc for charging the two batteries.Zener diode D5 keeps the voltage fromexceeding the approximately 8 voltsrequired for recharging. An optionalresistor (R1) is used to limit the chargingcurrent to a safe level.Construction. There is no practicalway of assembling the calculatorwithout the aid of a printed circuitboard. Unfortunately, since the boardmust have conductors on both sidesFEATURES OF THE POPULAR ELECTRONICSFULL -FUNCTION SCIENTIFIC CALCULATORBasic arithmetic: add, subtract, multiply,divideAny positive or negative number between1.99 x 10-99 and 1.99 x 1099 canbe entered and displayedEntry can be in either floating point orscientific notation, with automaticconversion to scientific notation invery large and very small numericalresultsAlgebraic problem entry with two levelsof parentheses10 -digit mantissa with 2 -digit exponentnumeric display, plus battery -low,minus -sign, radians, disallowed -function, battery saver display.Positive /negative sign selection for mantissaand exponentTranscendental functions: sin, cos, tan,sin-', cos -', tan-', common log, naturallog, ex, xYConvenience functions: \, 1 /x, xzSeparate memory register for storage ofconstants or intermediate resultsChain calculations with any sequence offunctions desiredIndependent system and entry clearTrigonometric functions can be performedin either degrees or radiansSeparate

and the components must bemoun' ,d as close to the board's surfaceas possible, there is no practicalway of making this board at home.While you might be able to make therequired double -sided board at homewith all points properly registered,there is no known method that can beused at home to plate- through theholes. Hence, you will have to purchasethe pc board from the supplierlisted in the Parts List.Shown in Fig. 2 is the component -placement guide for the main boardassembly. The view is from the componentside of the board. (The twosides of the board are readily identifiablebecause the bottom side onwhich no components are mountedbears the legend BOTTOM.)Start assembly by installing andsoldering into place the fixed resistors.Then proceed to installing thethree electrolytic capacitors, thediodes, and the transistors, takingcare to observe proper polarity andbasing. Mount the transistors closeto the board's surface. Use a fine -pointed soldering tip, thin -strand solder,and a minimum of heat. Frequentlyclean the soldering tip with adamp rag to remove excessive buildupof solder. This will minimize the possibilityof solder bridges between theclosely spaced foil conductors. Do nottouch or remove the MOS IC's (ICIand IC2) from their carriers until instructedto do so.If you inspect Tl, you will note thatthere are three pins in one of its corners.These pins serve as the installation"key." Install and solder intoplace the transformer. PotentiometerR3 mounts in the upper -right corner ofthe board. Then install IC3 through1C7 in their respective locations, carefullyobserving the notch code. As youproceed, carefully inspect the boardfor the presence of solder bridges. Ifyou locate a solder bridge, reflow thesolder and remove the excess.Install the two flat (negative) batterycontacts as shown. Solder them atboth ends and on both sides to thecopper conductors. (Note: There aresmall holes in the board and the batterycontacts are dimpled. Whenproperly installed, the contacts arepositioned with their dimples engagingthe holes.) Install and solder intoplace the spring -type battery contacts,making sure that the pin- connectorside is vertical to the plane of theboard. Mount and solder into placejack J1.56IC51JIBA TIT -IC6 IC7 1C3 IC4NOMMORMICI`11,f,A,l.i.1 .I. I..l.fLiI 1BAT T+\n\C2105AugICIC2nKEYBOARD CONNECTOR STRIPStraighten a strip of 24 MolexSoldercon connectors but do notremove the connector strip. Force theend pins of the strip through a 2V2 -in.by' /s -in. (16- x 3.2 -mm) piece of maskingtape from the non -adhesive side.Mount the connector strip in the holesjust below the five IC's at the top of theboard, pressing down to seat the tapefirmly against the board's surface. Flipover the board and solder the protrudingpins to the copper foil. Be verycareful to avoid solder bridges. Flipover the board again and, using long -nose pliers, bend the connector stripback and forth until it parts from theconnectors. Be careful to align theconnectors properly.In the same fashion as describedabove, mount a strip of 20 Solderconconnectors along the lower edge of.SATT-DISPLAYCONNECTORSTRIPFig. 2. Componentplacement on thecomponent sideof the pc board.BATT +DIRI(OPTIC3-^0 .,! x.:..y.ro4-ithe board. This time, use a 2 -in.(51 -mm) length of masking tape. (Theupper strip of connectors is for thedisplay interconnect, while the loweris for the keyboard interconnect.)Straighten four Soldercon strips,each consisting of 14 connectors. Installthese in the holes forlCi and IC2.Then, before breaking away the connectorstrips, make sure the connectorsare straight and that the IC pairsare parallel to each other. Now, beforeyou even consider opening the carrierin which IC1 and IC2 are packed, carefullyread and become familiar withthe procedures for handling MOS devicesby reading the instructions givenin the box on page 57.With yourself properly groundedand all conditions for good MOSdevicehandling met, open the carrier.POPULAR ELECTRONICSWith the IC's still in the carrier, determinewhich is which and the locationsof pins 1. Pin 1 is near the small bumpon each IC. To be absolutely certain ofpin 1 on each IC you can use a smallmagnifying glass to check the IC leadsnear where they enter the packages.Only pin 1 in each case has a tiny holedrilled through it.With the forefinger of the hand youhave grounded pressed against themetal plate on top of /C1 remove the ICfrom its carrier. Check to make sure itsleads are in straight lines. Then carefullyinstall the IC in its appropriateconnectors on the board. First engagethe pins along one side of the IC in theconnectors. Once this is accomplished,work the leads along theother side into their connectors. Applyfirm, even pressure to the IC to seat itin its connectors. Do not force the ICinto the connectors or subject it to torsionalforces or you might misalign oreven break off pins. If insertion is difficult,replace the IC in its carrier.Then, insert and remove an old IC inthe connectors several times to"form" them. Any DIP IC will do; justmake sure to cover all connectors.Now, install the IC from the carrier.Repeat the above procedure for /C2.The display comes as a completelywired assembly, with its 24 connectorpins already mounted in place. Justmake sure that the pins are in astraight line. Carefully fit the display -board pins into their respective connectorson the main board. Press thedisplay board into place so that it restson the five upper IC's with a slight tilt.The keyboard also comes as a completeassembly, including connectorpins. Straighten any out -of-line pinsand engage them in the connectorsalong the lower edge of the mainboard. Gently seat the keyboard assemblyin place until the narrower portionsof the upper two plastic posts onthe keyboard assembly engage thesmaller of the holes above thenegative -terminal battery contacts onthe main board.Slide the entire assembly into thetop half of the calculator case until thetwo small plastic tabs on the bottomend of the keyboard engage themolded slots in the case top. At thistime, two threaded plastic postsshould appear through the holes immediatelyabove the negative batterycontacts on the main board, and J1should slightly protrude through itsslot in the case.Holding the board assembly in placeJANUARY 1975in the case, secure the two together Checkout and Adjustment. Plugwith small nuts over the threaded the recharger into Ji and let the bat -posts. (Note: Because of possible in- teries charge for a few hours. Thenterference between nut and close -by disconnect the charger. Remove thefoil conductor near the left post, pre- tape from the power switch and set itcede the nut here with a thin insulating to ON. The right -hand mantissa digitwasher.)and its decimal point should comePlaceon,the power switch in the OFF displaying O. Leave the power appliedposition, and tape it in place until the and, after about a 30- second delay, thebatteries have been installed. The bat- 0 and decimal point will blank out,teries are marked with + and - signs. being replaced by a minus sign in theThe + sides are protected by sleevings exponent display. This indicates thatthat extend beyond the bodies of the the battery -saver feature is working.batteries. The sleevings are notched in Press the clear (C) key to restore O.such a manner that the batteries will fit to the display. Feed in the numbers 1into their respective locations in only through 0; operate the +/- and EEone way. Slip the batteries into place. (enter exponent) keys; feed in 88; andThis completes construction.press the +/- key. The display shouldnow read -1234567890-88. Press thedegrees -to- radians key; a smallSAFE HANDLING OF MOS IC'S diagonal bar segment should come onto the extreme left of the display. Op-Prior to any construction and before re- erate this .key again, and the barmoving MOS IC's from their protective should extinguish. Press the C key.carriers, it's imperative that certain pre- Press the n key. The display shouldcautions be understood and followed: now read 3.141592654. DepressAlf insulated C.-gate MOS devices can be Now, with O. displayedpermanentlyin eachdamagedcase,by excessively presshighlogelectronic(commonfields. logarithm),Random'1nelectrostaticcharges (naturalmust logarithm),be kept away fromand 1/x (recip-MOS devices. Anyone whorocal).handlesIntheeach case, before depresdevicesshould wear anti -static clothing sing C, the disallowed function indi-(preferably cotton) and, if possible, cot- cator, an inverted L, should show atton gloves. Do not wear synthetic fab- the far left of the display.rics, particularly nylon; they readily build To adjust battery -low indicatorup static charges.potentiometer R3, it is necessary toAll working surfaces where MOS de- first fully charge the batteries.vicesPlug theare handled should be conductive batteryandcharger intoJ1at ground potential.and theBeforeac outhandling,let. Withyou shouldthe poweralso be grounded.switch set to OFF,Andavoid dropping chargeMOS devicesthebecausebatteries forofabout 8 hours.possible contact with charged Thensurfacesuse the calculator for about 4or objects.hours. Then, with the power ON, adjustAll apparatus that is to come into con- R3 with a thin- bladed screwdrivertact with MOS devices must be through the hole in the bottom of thegrounded, including your soldering main board, until the battery -low indiiron'stip. Never insert or remove a MOS cator (an L at the left of the display)device in a powered circuit. When insert- comes on.ing or removing a MOS device, touch the Installgroundedthe back of thesurface calculatoronly after you havegrounded caseyourself.by insertingIf possible, the twogroundbottomthe conductor pattern "hooks"around intothetheir respectiveareaslots atwhere the device is to be installed the bottomwithend of the calculator. Theconductive tape or aluminum foil during top end simply snaps into place. A narinstallationand removal. When a good row slot at the top of the case is pro-MOS device is removed from a circuit, vided to permit the case to beimmediately install it in a protective car- reopened as desired with a coin orrier.screwdriver blade. Simply twist.You can ground the tip of your solder- The calculatoringcan beironoperated fromby wrapping around its thick fullyportioncharged batteries fora copper about 4strapto 5and fastening thestrap tohours. When the chargea length of meshed runscable. Thedown,free end of the cablesimplythen pluggoesintothe recharger. Rechargagoodground. To ground yourself, use ing takes 8 toa simi-10 hours. The batterylar procedure. Wrap a length of meshed charger can also be used as a convecablesnugly around your working -hand nient battery eliminator. However,wrist and connect the free end of the under no circumstances should thecable to a good ground.recharger be used if there are no batteriesin the calculator.57

S4TI-V TO OP AMPS +V01HEP 703RI711REVERSEOJI117 VACFI.SA26.8VCTC2R34.7KI 100y04HEP801DSCI +1000yFR44.7KC3100yFQ22N4400DS D6 D7NNN1N4003ICI741R210KIIII3(6V)J2TOTRACKS3 I S2STOP t- OEC? IimSIINC.Controller circuit is variation of apower supply regulator. Potentialon C3 determines track voltage level.PARTS LISTIC Speed ControllerforHO Model RailroadsPrecision low -cost device providesfull control flexibility and simplespeed indication optionWITH A PAIR of integrated -circuit operational amplifiersand a handful of parts, you can build aprecision speed controller for HOgaugemodel railroads at minimalcost. The solid -state controller featuresforward /reverse, stop, increase-speed, and decrease -speedswitches for full control flexibility. Inaddition, optional lighted pushbuttonswitches can be used to provide a vis-58ual indication of how fast the train ismoving on its tracks. The faster thetrain moves, the brighter the light fromthe lamps.About the Circuit. Operational amplifierIC1, in conjunction with transistorsQ1 and Q2 (see schematic diagram),forms a voltage regulator circuit.The output voltage from this circuitis determined by the voltage at theBY ROBERT D. PASCOEwiper at potentiometer R2 and the dcvoltage across capacitor C3. Op amp1C2 is connected in a voltage -followerconfiguration. The dc voltage acrossC3, the reference for the regulator, is aproduct of the time a constant currentis "pumped" into the capacitor. Thetwo current "pumps" in this systemare made up of the Q3 and Q4 circuits,with Q3 the negative and Q4 the positivepump.POPULAR ELECTRONICSC1- 1000-1.LF, 50 -volt electrolytic capacitorC2, C3- 100 -µF, 50 -volt electrolytic capacitorD1- D8- 1N4003 (or similar) silicon diodeF1 -0.5- ampere fuseIl -I3 -6 -volt pilot lamp (optionally in SI -S3)ICI, IC2 -741 operational- amplifier integratedcircuit (or use dual version)J1, J2- Banana jack (one black, one red)Q1- HEP -703 power transistor (Motorola)Depressing increase speed switchSi causes the output voltage at thetracks to increase. Conversely, depressingS2 causes the output voltageto decrease. And pressing stop switchS3 causes the output voltage to immediatelydrop to zero.A visual indication of the speed atwhich the train is moving is obtainedby observing how bright the light isfrom lamps /1- 13.One of these lamps is(optionally) inside each pushbuttonswitch. The greater the track voltage,the faster the train is moving on thetracks, and the brighter the lamps.The three -diode current limitercomposed of D5 -D7 holds the currentbeing fed to the tracks to approximately1 ampere. Hence, the circuit isprotected in the event the train tracksshould accidentally be shorted toeach other.Construction. Owing to the simplicityof the circuit, the entire controller,except for T1 and the switches, can bemounted on a piece of perforatedboard with the aid of push -in solderJANUARY 1975Q2- 2N4400 transistor (or use MotorolaHEP -736)Q3, Q4-HEP -801 FET (Motorola)R1 -0.7 -ohm resistor (four 3.3 -ohm, 'h -wattresistors in parallel)R2- 10,000 -ohm potentiometerR3, R4-4700-ohm, 1/2-watt resistorS1 -S3- Normally -open pushbutton switch(Use Switchcraft No. LUS -05 -01 if built -in6-volt lamp is desired)terminals and sockets for /C1 and /C2.Series -pass transistor Q1 must bemounted in an aluminum heat sinkwith about 9 sq in. (58 sq cm) of radiatingarea.You can mount the circuit board assemblyand transformer in any suitableenclosure. The control switchesand potentiometer are best mountedon the top of the enclosure, while outputjacks J1 and J2 are more convenientlylocated on the rear of the enclosure,as is the exit hole (strain relievedor rubber -grommet -lined) forthe line cord.In Use. The upper voltage limit to thetracks is determined by the setting ofpotentiometer R2. To adjust R2, depressincrease -speed switch S1 for 10seconds. The glow of the three lampswill increase in brilliance during thisinterval. Set R2 for the desired upper -limit track voltage.The speed atwhich the track voltageincreases and decreases is determinedby the two current pumps (Q3and Q4). With the componentsS4 -Spst slide or toggle switch55 -Dpdt, center -off switchT1- 26.8 -volt, 1- ampere transformerMisc. -Heat sink forQl; suitable enclosure;fuse holder; socket(s) for IC/ and IC2;perforated board and solder clips; linecord; strain relief or rubber grommet (forline cord exit hole); dry- transfer letteringkit; machine hardware; hookup wire; solder;etc.specified in the Parts List, the voltagechange rate is about 2 volts /second.Increasing the values of R3 and R4decreases the rate of change, andvice -versa.OSo why should the experimenter haveto start from scratch when we cangive it to them in kit form!59

The keyercombines pitchBY DON LANCASTERCA°4,uuu1u`Fig. 1. In a good keyer, pitchand envelope waveforms (aboveA) are combined to produce anote which is their mathematicalproduct (below A). Output ofpoor keyer (B) has excessivetransients; (C) has envelopein output; (D) has unequalpositive and negative swings.of the tone or waveshape without behavinglike a low -pass filter.To be useful in a circuit, the keyershould have a medium -to -high toneinput impedance and a low output impedanceso that it can drive outputand timbre circuitry without difficultyand does not load down the tonesource too heavily. The impedance atthe envelope input would ideally beinfinite so that large -value resistorsand economical small capacitorscould be used for attack- sustain -decayshaping. This is particularly importanton polyphonic instrumentswhere a hundred or more keyer circuitsmight be needed.Keyer design is no simple task, sinceit shares all the woes of any faithfulelectronic analog or digital multiplicationproblem. Let us look at somepopular approaches to keyer design.In this first part of our two -part articleon keyers, we will discuss diode,differential -amplifier, four -quadrantmultiplier, and gain block keyers. Nextmonth, JFET, MOSFET, Transconductance-amplifier and CMOS keyers.Diode Keyer. The diode keyer isby now, fairly obsolete. An ordinarysilicon diode has its small -signal(50 mV or less) ac impedance set bythe direct current through the diode. Ifthere is no current, the diode is anopen circuit. For small direct currents,the impedance presented to ac signalsis given by the ratio 26/I, where I is thecurrent in milliamperes. So, a diodecarrying a 0.5 -mA current "looks" like52 ohms to a low -level ac signal routedthrough it.In Fig. 2A, one capacitor is used tocouple a tone into the diode and usethe envelope information to set the directcurrent through the diode. Thedisadvantage of this circuit is that itwill thump as the envelope appears inthe output. A second diode and equalpositive and negative signal swings(Fig. 2B) from the envelope circuitryovercome this disadvantage. The twodiodes are in series across the envelopecircuit but in parallel with thetone input. Two more diodes (Fig.2C) eliminate the extra couplingcapacitor.Input impedance is low, output impedanceis high, and a wide voltageswing into a medium resistive load isneeded for the envelope input. But ifthe diodes are identical and if the controlvoltages are also identical, and ifthe ac signal level is low enough, thediode keyer can operate without introducingintolerable distortion, and itand envelopeinformation inan amplifier to shapea realistic mode.KEYING circuits go by manynames. In organs, they are calledsimply keyers; in traditional electronicsynthesizers, they are often calledvoltage -controlled amplifiers (vca's),envelope shapers, or modulators.Functionally, they are electronic multipliers.All of them do the same job --they combine pitch information withthe envelope information to produce arealistic note or note sequence.Done properly, this sets the attack,sustain, fallback, decay, and snubbingof any note on an individual basis. Envelopecontrol can also introducesuch special effects as percussion, the"bite" on the leading edge of a hornsound, echos, tremelo, and noisemodulation.60A very few older organs did not employkeyers. They simply applied andremoved the supply voltage to andfrom oscillators or used the keysthemselves as off /on note controllers.Envelope shaping ability is very limitedby this means. At the other extreme,some true computer composingcircuits and programs completelyspecify the amplitude and frequencyinstantaneously. With these exceptions,virtually every other electronicmusic system generates tones and envelopeinformation separately. Thesetwo signals are then routed into a circuitthat provides a combi nation of thedesired loudness and frequency.The keyer or vca might work on anynote in a monophonic instrument, orone individual keyer can be suppliedwith each note in a polyphonic system.We can use much more sophisticatedkeying circuitry if we need only a few,rather than one for each note. Keyingor envelope shaping can take placeeither before or after the tinbre ortone -quality circuitry, working eitherwith the raw frequencies as generatedor the final highly structured harmonictone. Organs usually employfixed formant filters; and a polyphonicinstrument is usually keyed firstand voiced later. In synthesizers, thenote will more often be colored by apatchwork of voltage -controlledoscillators (vco's) and filters (vcf's),and then envelope shaping takesplace.POPULAR ELECTRONICSWhat a Keyer Does. Any keying circuitmust simply control the gain ofthe tones fed through it. In Fig. 1 areshown some good and some badthings keyers do. The keyer must behaveas a linear, electrically bilateralvariable resistor. Ideally, it must introduceno coloration or significant distortionof its own (Fig. 1A).A keyer must be transient -free. Thismeans that no ringing or overshootcan be permitted as in Fig. 1 B. It alsomeans that no feedthrough of the envelopeinformation to the output canbe permitted (Fig. 1C). The result offeedthrough is a loud thump and otherresponse- recovery problems later onin the circuit. Any keyer circuit inwhich the dc output level changes as afunction of the envelope command isbound to be a bad design and willthump badly.A keyer must treat positive andnegative signal swings equally, amplifyingor attenuating them withequal gain (Fig. 1D). And the keyer systemmust have a wide enough frequencyresponse to follow faithfullythe envelope and pass all frequenciesJANUARY 1975of \_.ENVELOPE /NP//Toyo VOLTSraVE /NPUTSn M/LL/ VOL TS,tiWW10Fig. 2. Simplediode keyer (A)thumps as envelopeappears in output.Two diodes (B) µuu o-OPOS /r /VEENYEL OPE /NTONE /NPNTeliminate most of f SO M/Ll/ POETSoutput thumping.Four -diode version NE6-4 r/VE6ÓVELOPE(C) saves onecapacitor and haslower distortion. -/orONE/N.FiuFa)(C)/OKNOTE o4TPuT' o- 5oM /LU VOLTS/o o J./00 .12ÉNVEL OPEEN VEL OPENOTE OL/TP[/ J-o -SO ,G/ /LL /VOLTSNOTEOur61

will not cost much to make. (A diodekeyer will always add some distortion.)Various transistor schemes havebeen used in keying setups. They arebasically diode keyers that use thebase -emitter junctions of transistorsas the multiplier elements. They easethe loading and impedance problems,but they can introduce thumping ifthey are not properly designed. Today,we have much better methods.Differential Amplifier. In Fig. 3A isshown a differential amplifier. It is themost commonly used amplifying circuitat this time and is found in almostall linear integrated circuits. A differentialamplifier normally amplifies thedifference between two input signals.In Fig. 3A, one input is tied to groundto provide single- ended -input operation.This circuit can be used as akeyer by routing the tone signal intoinput X and the envelope into input Y.If a fixed voltage is applied to inputY, some emitter current will appear inQl and Q3. Input A goes to Ql andcomes out of the transistor's emitter.The emitter signal drives Q3, which isoperated as a grounded -base stage,and an amplified version of the inputsignal appears at Q3's collector.The gain of the circuit in Fig. 3A isobtained from the formula IR/104where R is the Q3 collector load resis-tance in kilohms and I is the emittercurrent in Q3, the 104 comes aboutbecause Q3 receives only half thevwMn ,t/ÑPUT/oomo ENVELOPE/NPid/o V t/OV-f5- 02-R(A)NOTEOUTP4/T.3 r o4-rS03available current and because Q1'soutput impedance is equal to the inputimpedance of Q3, which yields a secand2:1 attenuation.It is important to note that the gain isdirectly proportional to the emittercurrent. Change the voltage on inputY, and the gain changes, and theproduct of the envelope and toneinput signals is obtained. This type ofcircuit is called a vca. It bilaterally andat high speed gives the product of thetwo input signals.One obvious problem with this circuitis that the dc drop across Q3'scollector load resistor follows the envelope,resulting in two outputterms -the desired shaped tone andan undesirable thumping from envelopefeedthrough. In Fig. 3B, a secondload resistor, in the collector circuitof Q1, has been added. This circuithas two outputs, one of which isin -phase and the other out -of -phasewith the input. Both outputs bounceup and down together.A good differential amplifier ignoresthe common -mode up- and -downbouncing of the input signals. It is onlythedifference between the two signalsthat matters. So, by simply adding stillanother differential amplifier stage tothe one shown in Fig. 3B, the outputstays at a fixed dc level regardless ofthe envelope and is a thump -free replicaof the desired signal.Differential amplifiers are widelyused in synthesizer vca's. While manytsvTO4/0/NPVT3VA>/ÉNVtt oPE/NP/JTS/ c49.4 Hlr,4EASO. PfYASEfy/rksimilar devices exist, the RCA CA3000series linear IC's offer many differential-amplifier possibilities. An ordi-nary 741 or 5558 operational amplifiercan be used to eliminate thecommon -mode thumping on the laststage. The differential -amplifier vcaoffers good input and output impedances,controllable gain, and largesignal swing. The envelope signalmust be referenced to a negative supply,and the input impedance mightbe a bit lower than we would like it tobe. Dynamic range is good and distortionis low, but the system becomesa bit complex if a separate circuitis used for each polyphonic note. Thedifferential -amplifier vca is a verygood choice for monophonic synthesizercircuits.t/OVaak ; a.a,eS/64441.. NEREp/Four -Quadrant Multiplier. A fou r-quadrant multiplier is a true electronicmultiplier that provides the product ofthe envelope and pitch inputs directly.No offsets are needed on the envelopeinput, and the output is normally referencedto ground.A typical four -quadrant multipliercircuit is shown schematically in Fig.4. The multiple paths through all thedifferentially- arranged transistorsprovide for automatic cancelling ofcommon -mode feedthrough andthumping. As a sometimes handygimmick in some advanced synthesizersthe phase of the tone signal is reversedby inverting the envelope.u OvIN PHA 5Ely/r// /NPx/s-ç3*2fa)/o..Psi 964 0Fig. 3. In basic differential amplifier (A), envelope causes thump in the output. An additional amplifiercan be added (B) to eliminate thump. Second stage can be an ordinary 741 operational amplifier.pSNOTEourPu/rSECOND O/FR AMP.AIN/A/F/ES D/FFERCNCiBErjveENQ/4tp.jour-Pans BF/T /6-NQ2E5GOMNCn/ MDOa.TN//MP/N!rFig. 4 (A) are typical connections for 4-quadrantmultiplier. Key internal circuitry is shown at (B).Typical four -quadrant multiplierIC's include Motorola's MC1595 andAnalog Devices' AD532. Alternatively,you can use the much lower pricedSignetics 5596 as the key componentJANUARY 1975in a multiplier of your own design.The only real disadvantage with thefour -quadrant multiplier is its cost.None of these IC's is inexpensive.Some exceed $20 each and obviouslyare too costly if you are consideringusing one for each note in a polyphonicsystem. Aside from this, thefour -quadrant multiplier is just aboutthe best you could hope for.Gain Block. Several linear IC's offerremote -controlled gain capability thatcan be used as a keyer circuit.Motorola's MFC6040 is a typical exampleof such a circuit (Fig. 5). It costsabout $1. Its circuit is one more varianton the differential -amplifier theme+16 VIMATONEINPUTloom V1.0µFEMVEIOPEl_f-/NPU1-3.5 1,01-TS= OA/7 5.f VO .s aFcFig. 5. Gain blockenvelope shaper.4MFC60406.00O4FÌlilNOTE.OUTPUT3OorVwith common -mode bucking. Typicalvoltage gain, wide open, is 3:1 or 10dB; attenuation can go as low as 70 dBbelow full output.The output swing of the MFC6040can be up to 6 volts peak -to -peak. Onepotential disadvantage of the circuitis that the attenuation is somewhatnonlinear.pSCANNING MONITOR RECEIVERSHF /FM VHF /FM UHF /FMNow -the "Sentinels ", a series of finemonitor receivers joins the big, worldwide-accepted line of SBE communicationsequipment. Single or dual bandmodels of these versatile, application -oriented SBE scanners provide coverageof the most widely used VHF /UHF bands.For example, the six different receiversavailable give FM reception and positivescanning operation for business, industrial(including RCC and other mobile telephone),law enforcement, fire, highwayemergency, traffic advisory, marine -includingintership / Ship -to -shore / CoastGuard /Weather - many other services.SIX MODELS:Sentinel I: HI- 144 -171 MHz, Lo, 30 -51 MHz.Sentinel II: 144 -171 MHz.Sentinel Ill: 30 -51 MHz.Sentinel V: 450- 470MHz.Sentinel VI: Hi- 450- 470MHz,Lo- 144 -171 MHz.Sentinel VII: Marine, 156- 164MHz.VOLUMEsQteLCH8 channels- continuous "scanning ".Receiver locks on first channelon which signal appears.Priority channel feature: Receivershifts instantly to designated channelwhenever carrier appears on itregardless of existing channel status.Channel lock -out buttons: Unwantedchannels can be locked out.Manual advance button allows channelsto be scanned manually.Base or mobile (AC or DC). Use incar or home /office. Operates bothon 12VDC for mobile and 115VAC forhome station.CIRCLE NO. 32 ON READER SERVICE CARDail ifflal®!-Sentinel IBig audio volume -3 to 4 watts.Fractional microvolt sensitivitySquelch Built -in speaker Jackfor external speaker Crystals usedare readily available types not included).Complete w/ plug -in telescoping antenna,mobile mounting bracket and cord,plug sets for 12VAC and 115VAC.Write for Brochure1---1=14 LINEAR SYSTEMS, INC.220 Airport Blvd., Watsonville, CA 95076.63

The better thethe betterCOMPU- TRAINERTUBE & TRANSISTORTESTERSOLID STATEOSCILLOSCOPErnÇequipmentbe equipped.IN- CIRCUIT TRANSISTOR TESTERHIGH FIDELITYSPEAKERSSOLID STATE STEREOAM FM RECEIVERAMPLIFIERCOLOR BAR /DOTGENERATORDIGITALMULTIMETERLO-SILHO --SUPERHET RADIO' ' tVECTOR MONITORSCOPESOLID STATEB &W TVELECTRO - LABAs an NTS student you'll acquire the know -how thatcomes with first -hand training on NTS professionalequipment. Equipment you'll build and keep. Ourcourses include equipment like the 5" solid -stateoscilloscope, transistor and tube -tester,vector monitorscope, 74 sq. in. B &W TV, and solid state stereoAM -FM receiver. The unique NTS Digital GR -2000color TV with first ever features like silent varactordiode tuning; digital channel selection, (with optionaldigital clock,) and big 315 sq. in. ultra rectangularscreen. This is just a sampling of the kind ofSimulated TV receptionNTS DIGITAL GR -2000 SOLID STATECOLOR TV WITH 315 SQ. IN. PICTUREAND VARACTOR DIGITAL TUNINGTROUBLESHOOTERVOMbetter equipment that gets you better equipped forthe electronics industry.This electronic gear is not only designed for training;it's field type - like you'll meet on the job, orwhen you're making service calls. And with NTSeasy -to -read, profusely illustrated lessons you learnthe theory behind these tools of the trade.Choose from 12 NTS courses covering a wide rangeof fields in electronics, each complete with equipment,lessons, and manuals to make your trainingmore practical and interesting.NT:'OSCILLOSCOPESIGNALTRACERFET - VOMr;npare our training; compare our tuition. We emoyno middlemen because we need no salesmen.TUI a believe you have the right to make your own de -.PRt1sions based on the facts, and you'll find these allMApelled out in our catalog mailing. Lessons, kits, andFAS'Veriments are described in full color. Most liberalPRE &nd policy and cancellation privileges - it's all incatalo g. And our low tuition is another big advantage.oncoú Ils, no commissions to pay. This means lowerNo OB,n for you. You receive solid training value. NTSNo sAtnore into your training, so you get more out ofSOLID STATE 2 -METERFM TRANSCEIVER ANDPOWER SUPPLYSOLID STATEPOCKET RADIOSIGNALGENERATORit. Make your own decision. Mail the card, or write ifcard is missing. There's no obligation, ever, and nosalesman will call.Approved for Veteran Training. Get facts on new2 -year extension.NATIONAL TEC

THE tuner is the "radio" portionof your music system. Althoughmost tuners cover both the AM and FMbroadcast bands (and proposed governmentlegislation will make thismandatory), the following commentsapply specifically to FM tuners.The tuner's function is to separateone desired signal from the many interceptedby the antenna, amplify itmillions of times, convert its frequencymodulation to an exact facsimileof the original program, and (if itis a stereo program) subject the detectedsignal to a complex processwhich separates it into left and rightstereo channels.Like amplifiers, most tuners tend tosound pretty much alike on ordinaryprogram material. Many people placegreat store in numerical specificationsfor such characteristics as sensitivityand selectivity. Actually, neither ofthese is easy to reduce to a single convenientnumber that defines that aspectof the tuner's performance.Numbers are used, of course; but theyare frequently misunderstood or misinterpreted.Sensitivity. This refers to the abilityof a tuner to receive a weak signal withacceptably low noise and distortion.The IHF Usable Sensitivity rating ismost often quoted, although it doesnot correspond to a really listenablesignal. Most good tuners have an IHFsensitivity of less than 3 pM, and someare as low a8 1.5 µV. Although in practiceit would not be possible to detectany real difference between two tunerswhose sensitivities differed by afactor of two (all else being equal),there is a tendency to make much ofdifferences of a few tenths of a microvolt,a quite insignificant amount.More meaningful is the 50 -dB QuietingSensitivity rating included in aproposed IHF tuner standard, but notyet in wide use. Our test reports inPOPULAR ELECTRONICS do include it,however. This is usually in the range of3 to 7 µV and represents the weakestmono signal that can be receivedwithout excessive background hiss.For stereo reception, all these sensitivityfigures should be multiplied by afactor of ten, which may explain whystereo sensitivity ratings are notwidely publicized!Of course, these sensitivity numbershave no absolute meaning to the consumerwho cannot know the actual receivedsignal strengths in his area. Inrural locations, one can indeed findsignals of a few microvolts, and sometimesthe highest possible tuner sensitivityis needed in such locations. Inmost urban and suburban locations,the tuner receives from its antennahundreds or even thousands of microvoltsfrom dozens of stations.Selectivity. Clearly, high sensitivityis not likely to be an important tunerrating for the city dweller. What aboutselectivity? FM stations in any givenarea are assigned to channels at400 -kHz intervals (alternate channelspacing). If you are located close to apowerful FM station and wish to receivea far -off station only 400 kHz removed,you will need high alternate -channel selectivity. Most FM tunershave selectivity ratings between 45and 60 dB, which is generally adequatefor interference -free reception.If you have a "problem," there aresome tuners whose alternate -channelselectivity is 90 dB or more. They areexpensive, but well worth it if you needtheir special qualities.In strong -signal areas, some tunersare subject to spurious responses-signals appearing on the dial in unexpectedplaces and sometimes interferingwith a desired signal. The relevantratings -image rejection, spuriousrejection, i -f rejection -are alsoexpressed in decibels, with the highernumbers being better.Capture Ratio. A major cause of distortedFM sound is multipath recep-tion, caused by a signal reflectingfrom various structures and reachingthe antenna from different directionsand at slightly different times. Thetuner specifications related to lowmultipath distortion are capture ratio(the lower the better, with most goodtuners under 3 dB and the best reaching1 dB or less), and AM rejection(ratings in excess of 50 dB are good,and a few are as high as 70 dB). Youshould be aware that no tuner can becompletely immune to multipath distortionand that the best cure for thisand most other FM reception problemsis a good directional antennawhich can be rotated to obtain bestresults.The tuner distortion rating shouldbe well under 1 %, and most good tunersare rated between 0.2% and 0.5%in mono, and about twice as much instereo. Stereo channel separation varieswith modulating frequency, but isoften specified at 400 Hz or 1000 Hz,where it is greatest. Comprehensiveratings include a definition of separationover a range of frequencies, suchas 100 to 10,000 Hz. If the separationexceeds 20 dB over most of the audiorange, you can be assured of a satisfactorystereo effect. Many tuners inall price ranges have 30 to 40 dB ofseparation over most of the audioband.Operating Ease. Many importanttuner differences relate to their ease ofoperation, rather than their electricalperformance. The tuning dial shouldbe legible and well calibrated. (Sometuners, even high -priced units, are difficultto set accurately to a known frequencybecause of inadequate dialcalibration.) The tuning "feel" shouldbe smooth and positive. Tuning indicators,whether meters or lights,should give an accurate indication ofcorrect tuning. Interstation-noise mutingcircuits should be free from burstsof noise as one tunes through a station(although many are not). All of thesecharacteristics are easy to judge foryourself and require no technicalknowledge.There are several tuners with digitalfrequency readouts instead of theusual slide -rule dial. This eliminatesany problems of dial calibration butadds appreciably to the cost of thetuner. Compensating for their higherprices is the fact that most digitaltuners also have above -average performancein most other respects relatingto high fidelity. Q.BUILD THEIdentifies leads on unknowntransistors, indicates PNP or NPNpolarity, and shows up bad devicesMOST experimenters have adrawer full of unidentified transistorswhich are of little use unlessthe leads and type (pnp or npn) canbe determined. Actually, that's theonly really important informationneeded to apply a transistor in acircuit -assuming it is "good" tobegin with. Of course, it's nice toTRANSISTOR IDENTOMETERBY JOHN T. BAILEYknow what the transistor's beta is, butthis is not essential in many applications.The Identometer was designed toprovide a quick check of a transistor'sleads and type. It operates on thebasis that bipolar transistors willoperate, but poorly, if the emitter andcollector leads are interchangedwithout also reversing the powersupply. Since a transistor has threeleads, it is possible to connect themin six different ways. With a transistorplugged into the test circuit, theIdentometer has a switch to make thesix different connections. When theright one is selected, an indicatorlight comes on. The light also tellswhether the unit is npn or pnp.Circuit Operation. A schematic ofthe circuit is shown in Fig. 1. Notethat T1 has two secondaries, oneserving as the power supply for theQ/-LED/ and Q2 -LED2 circuits andthe other for the unknown transistor.Transistor Q1 saturates when theupper secondary voltage is in thepositive half cycle and its base ispositive. Transistor Q2 saturateswhen its collector has a negativevoltage and its base is negative. Thetwo transformer secondaries must bein phase as shown by the small dotsat terminals 1 and 3.The circuit is equivalent to anexclusive OR logic device, which hasan output only when the two inputsare at different levels. The high or lowsignal requirements are provided bythe transistor being tested and theinstantaneous polarity of the ac lineat the moment. The combination isone polarity for npn transistors andthe opposite polarity for pnp types.68POPULAR ELECTRONICS69

4WWRED IGREEN.solT23DIIN4001RI`IKLEDI01HEP736- . POES,?>911%D31N9140214001143 S2 2.D41N914N02HEP7I5PNPLED2t r7 ri n FT t 17YELLOW 1 1 1 11 I l jI I !This distinction provides the typeidentification.With the correct phasing of the 3 -4secondary of Ti, the exclusive ORsignals are accepted by the LEDdriver that can react to a compatiblesignal during its half cycle of the ac.Diodes D3 and D4 prevent slightdifferences in the voltage levels fromturning on the drivers.Construction. To duplicate the pro-7084)IR2IK:. .totype and use the pc boards shownin Fig. 2, certain mechanical modificationsmust be made to two of thecomponents. Transformer Ti musthave ils four terminals cut to a sizethat can fit into the pc board. Asshown in Fig. 3, two more tabs mustbe added to terminate a new winding.The molded plastic form of thistransformer allows adding the twonew terminals (3 and 4 on theschematic). The six terminals willFig. 2. Foil pattern formain pc board is at left,with component layoutat right. Foil patternabove is for rotary switch.PARTS LISTSD1, D2- 1N4001 diodeD3, D4 -1N914 diodeLEDI, LED2- Light- emitting diode (CalectroK4 -559 or similar)QI- HEP736 transistorQ2- HEP715 transistorR1 -R3 -1000 -ohm, 1/2-watt resistorR4- 18,000 -ohm, 1/2-watt resistorSl -Spst switchS2 -3 -pole, 6- position rotary switch (Mallory3236J or similarSOI- Molded transistor socketT1 -12 -volt, 300 -mA filament transformer(Radio Shack 273 -1385, modified per text)Misc.- Plastic case (Radio Shack 270 -231),Insulated miniature alligator clips (red,green, and yellow; Radio Shack 270 -378),knob with pointer, line cord, mountinghardware, press -on type, etc.RED --rFig. 1. Transistor being testedis plugged into SO1 or connectedto color -coded alligator clips.then be spaced three on each side, on3 /8 -in. centers.Wind 46 turns of #34 enamelledwire around the original core. Thereis enough room to do this, although itwill take a little patience. Be sure thatthe new winding is wound in the samedirection as the 12 -volt windingalready on the transformer to ensurecorrect phasing. (Don't scrape theenamel off the wire.) If you shouldwind the new secondary the wrongS2,Y-40*IYELS2,x -4*2AC LINEyGRNS2,2-*3 __---4)LED 2,A-4/ISOCKETBOTTOMVIEWS2,1 ! -0-- R4---*R2 D4 T.02r AC LINE.0-S2, 30--52,2.-LED1,A0-R3-1111 0-LED1,K7RIOI1POPULAR ELECTRONICSway, it is easier to route the ends tothe correct terminals than to startover or modify the pc board.The terminals of S2 must bemodified as shown in Fig. 3 so thatthe switch will fit the pc board asshown in Fig. 2.Now you are ready to assemble thecircuit on the main board as shown inFig. 2. The front panel is marked asshown in the photograph with the sixswitch positions identified. InstallSol and mount the LED's in smallrubber grommets, properly identified.PRIMA\ YTIADDED SECONDARY46T #34 ENAMELBEFORECLIP OFFAFTERSWITCH LUGDETAILFig. 3. Add a winding andterminals to the transformerand alter switch lugs as shown.Then mount the switch on the frontpanel. Connect the larger board to itwith spacers. Note that the largeboard has a small spacer supportingit from the hole drilled near the centerof the rotary switch board.Drill three small holes for thecolored test leads and put grommetsin the holes. The leads are terminatedwith color -coded insulated alligatorclips. From the top of the panel, thelowest test lead (green) is on a linefrom the emitter terminal on SO1; thecenter lead (yellow) is the base; andthe upper lead (red) is the collector.Operation. Connect the threecolor -coded test leads to the unknowntransistor in any order, turn onthe power, and rotate S1 until one ofthe LED's illuminates. Make sure thatthis only occurs at one position. Theposition of the switch will thenidentify the leads and the LED willindicate the type.If the transistor being tested is notgood (either open, shorted or leaky),neither indicator may come on or oneor both may light at more than oneswitch setting.The Identometer will not checkFET's, nor will it work "in circuit."When checking power transistors,particularly germanium types, theremay be some unpredictable resultsdue to the high leakage currentassociated with these transistors. OJANUARY 1975SimpleSquelchingCircuit forStereo FMTunersMANY inexpensive stereo FMtuners have no automatic"squelch" to eliminate between -stationhiss. However, they invariablyhave a stereo indicator lamp that canbe used to trigger a very simplesquelching circuit like that shown inthe schematic.The add -on squelch circuit shownemploys an inexpensive photo Darlingtonamplifier (HEP1001), operatingwith its base connection "floating".The Darlington amplifier switchesfrom a very high resistance in darknessto a very low resistance whenilluminated by relatively low lightlevels. When the photo transistor isswitched to low resistance, essentiallythe supply voltage from the batteryis applied across the gate- sourceterminals of both HEP 802 FET's. Thispinches off the FET's and causes themto present a very high source-drain resistanceacross the outputs of thetuner, effectively doing nothing.When there is no light present, thephoto transistor presents a high resistanceto the gates of the FET's. Thesource -drain resistance of the FET'stherefore drops to about 200 ohms,effectively short- circuiting the outputsof the tuner.LoTUNEROUTPUTSLIGHT FROMSTEREO INDICATORLAMPN.0RHEPP100 I* SEETEXTBY LAWRENCE N. DWORSKYIf the tuner being used has an exceptionallylow output impedance-less than 600 ohms or so -the between-station muting may be insufficientwith this setup. In this case, a100 -ohm resistor placed in each outputline of the tuner (see phantomedportion of schematic) should remedythe problem. Since most amplifiershave a relatively high input impedarice,these resistors should have noeffect on system performance.No power switch is needed with theadd -on squelch circuit because batterydrain is very low. Even whenoperating at full capacity, the drain isless than 10 IA. So, the battery will lastjust about its shelf life with power continuouslyon, which eliminates thebother of having to remember to turnon an extra power switch.When installing the squelch circuit,use only shielded audio cable to makethe hookups between tuner, squelch -er, and amplifier. Also, mount the Darlingtonamplifier as close as possibleto the stereo indicator lamp in thetuner. This transistor is very sensitive;so, care must be taken to insure that it"sees" light from only the stereo indicatorlamp and not from any otherlight sources.MEPHEP802DLCAMPNPUTSR71

MAC'S SERVICE SHOPif IT'S TIME we furthered your edu-IIby discussing lightning-damage insurance jobs thatcome into the shop," Mac announcedto Barney his assistant, during theirafternon Coke -break."A man can't even enjoy a Cokearound here without having it lacedwith knowledge," the red -headedyouth grumbled, "but go ahead -ifyou must.""That's what I like: an enthusiasticlistener," Mac said, lighting his pipe."There are three entities involved inthis kind of a job, and each must beconsidered: the owner of the damagedelectronic equipment, his insurancecompany, and the service shopcalled upon to assess the nature andextent of the damage and possibly torepair it. Let's run quickly through thechronology of such a job; then we'll goback and discuss interesting features."First, an insured who thinks lightninghas damaged his radio, TV,hi -fi, amateur station, CB transceiver,etc., should promptly report this to hisinsurance agent, who will instruct himto get an estimate of the damage froman established service shop. (Thatdoesn't mean the insured's brother -in -law who tinkers around with electronicsin his spare time!) At the shop,a technician carefully examines theequipment to see if the set failure wascaused by lightning, the extent of thedamage, and the probable cost of repairingthe set. This information is relayedto the insurance agent, directlyor through the owner, and the agentcalls an adjuster to look at the set. Itmay be a few days before the adjustercalls at the shop; but when he does, hewill want the technician to show himhard evidence that lightning did thedamage; so all such evidence shouldbe carefully preserved for his inspection."The adjuster reports to the insurancecompany, which, based on hisrecommendation, either (1) denies allresponsibility due to a lack of evi-72By John T. Frye, W9EGVdence that the failure was caused bylightning, (2) authorizes a repair of theset, or (3) because the cost of repair isprohibitive, makes some cash or replacementarrangement with the insured.The company pays for the estimatein the last two cases; the customerpays in the first. At any rate, thebill is made out in triplicate: one forthe customer, one for the insurancecompany, and one for our files. Thecustomer pays us, and we give himtwo receipted copies of the bill. Heturns one over to the insurance company,and they send him a check.""Why might a person think lightninghad damaged his equipment ?""Such circumstantial evidence canvary all the way from a coincidence inwhich the set would not operate immediatelyafter a heavy thunderstormto much stronger evidence in which aball of fire comes out of the TV set atthe same time there is a snap of lightningfrom a nearby stroke, followed bysmoke curling out the rear of thecabinet.""That last reminds me of Thoreau'sremark: 'Some circumstantial evidenceis pretty strong, like finding atrout in the milk.' How does lightningusually reach the equipment ?""In the case of a receiver attached toan outside antenna, the stroke or inducedvoltage surge can come in onthe feedline, but more often it entersvia the power line. A bolt doesn't haveto strike the line for this to occur. All ithas to do is strike in the vicinity. Afterall, the current of lightning strikes hasbeen estimated to be as high as200,000 amperes, with 15,000 to20,000 amperes being an averagevalue; and the voltages producing thestrike are estimated to be as high as100,000,000 volts. Lasting only microseconds,such a strike produces atremendous field that induces a voltagesurge on the primary of a powerline that can leap across to a transformersecondary and enter the housethrough the ac wiring. This surge caneasily bridge open switch contacts ofa radio or TV receiver. Most peopledon't understand this."What kind of damage does lightningdo ?""Mark Twain remarked that onething you could lie about and get awaywith was to tell something you heard aparrot say. Lightning stories are likethat. No one can prove you're lying.I've seen lightning strike a horizontalantenna and reduce it to a line of littlecopper beads in the grass below.When a conductor carries a heavy current,forces are developed by the accompanyingmagnetic field that tendto crush the conductor. This is calledthe 'pinch' effect. Another time I saw arubber -covered copper wire that hadbeen hit by lightning and reduced toa rubber tube with no wire inside atall. Stranger still, the rubber insulationseemed to be intact and hardlyscorched. More common effects includethe fragmentation of line bypasscapacitors, melted power switch contacts,fused conductors on pc boards,vacuum tube envelopes shattered,ADJUSTTO GROUNDNO.4 ORLARGERSAME SPACING AS FEEDERSFig. 1. A spark gap arrestor toprotect ham antenna is easily made.ruptured filter capacitors, shortedwindings in power transformers, antennainput coils of radios and TV setsbadly charred, flash burns on thechassis in the vicinity of line cord tie -points or the power switch, and tubeswith burned out filaments. These aresome of the things the adjuster willexpect to see.""I imagine the action the insurancecompany takes depends a lot on thepolicy the owner has.""Right. The usual home owner'spolicy comes in a variety of types, includingvarious deductible amountswith matching premiums. Naturally,the higher the deductible the lower thepremium. TV, amateur, and CB antennas,rotators, and towers are not ordinarilycovered by policies that are writtento cover the house, garage, andhousehold goods. Even then, withPOPULAR ELECTRONICSsuch a policy, TV sets, radios, andhi -fi's are only covered for their actualcash value. The guy who has neverread his policy carefully may be verychagrined to discover the total loss ofhis beloved but ten -year -old hi -fi doesnot entitle him to a brand -new stereosystem at the expense of the insurancecompany. He may do well to recoverthe cost of a new stereo cartridge.SPARK GAPHIGH-WATTAGENONLINEARRESISTORI IT VACSTEP -DOWN¡f POWER TRANSFORMERFig. 2. In power -line arrestor,current is reduced by resistor."But there's another way to go. If hehas ham, CB, or hi -fi equipment worth$500 or more, he can insure it for fullreplacement value with a separate policyusually labeled a 'personal linefloater' or an 'inland marine floater.'Then, if his equipment is destroyed,the company will pay enough to buy anew system comparable to the one hehad before. Such policies cost from80e to better than $2 per $100 of declaredvalue per year, depending onthe individual company and the iteminsured. Jewelry, cameras, tools, serviceinstruments, and similar equipmentin the home can be insured withthese policies.""Seems to me the technician ispretty important in this operation."That he is. Actually I do many insurancejobs here without ever seeing anadjuster. Local agents know me, andthey also know the average adjusteris unqualified to assess damage tosophisticated electronic equipment.They're content to use my report asthe basis for settling the claim. I'msure this arrangement prevails inmany other communities, and it puts alot of responsibility on the technician,especially when the equipment belongsto a long- standing customerwho feels 'taking' an insurance companyisn't really stealing. When one ofthese starts hinting he wants me todeclare his equipment a total losswhen it isn't, or to say the damage wascaused by lighning when there's noevidence to support this, I suggest thathe take his set to another shop be-JANUARY 1975cause I intend to call things exactlyas I see them. Invariably, he thenbacks off.""What do you think is the best insurancepolicy ?""That's easy: prevention. You rarelyrecover your entire loss through insurance;so the best thing to do is tryto protect your equipment from lightningdamage. You could, of course,follow the practice observed in the oldFrench provinces and keep somewood from a lightning- struck treeunder your bed, secure in the beliefyou're fully protected because 'lightningnever strikes twice in the sameplace'; but I'd suggest you employmore scientific methods. Start by makingsure your house wiring is properlygrounded and protected against overloadswith fuses or circuit breakers.Install U.L.- approved arrestors on allTV lead -ins, antenna rotator controlwires, and coax feed lines. Groundmetal towers or metal masts mountedon poles or other wooden supports.Make a good common ground. If youdon't know how -most peopledon't -order "Lightning ProtectionCode 1968," NFPA No. 78, from theNational Fire Protection Association,470 Atlantic Avenue, Boston, MA02210, for a postpaid price of $1.37.""How do lightning arrestors work ?""There are many types, but all areintended to do one job: carry a heavysurge of lightning- induced current ina conductor safely to ground, whileleaving that conductor virtually disconnectedfrom ground at all othertimes. Let me sketch a couple ofcommon types. Shown in Fig. 1 is ahomemade spark gap arrestor for useon the open -wire feeders of a ham antenna.Gaps are spaced just wideenough not to arc with full power fromthe transmitter, but voltage from anearby discharge will start the arc thatcarries the heavy current safely toground. When the surge subsides, thearc stops."Things are different when the conductornormally carries heavy currentand high voltage, as does a power lineprimary. Once the arc is started bylightning, the follow- current from thegenerator would keep it going untilthe arc electrodes were melted. Thearrangement in Fig. 2 prevents this.The nonlinear thyrite resistor hasa resistance which decreases exponentiallywith increasing current.When carrying the heavy dischargecurrent, it is a virtual shortcircuit; butwith the lower follow- current, the re-sistance increases until the voltagedrop across it is sufficient to stop thearc. Various resistance and gap typesof lightning arrestors are manufacturedfor use with telephone lines, coaxialcable, twin -lead, etc."But remember I said most damagefrom lightning occurs when a surgecomes in on the house wiring. That'swhy I think it is an excellent ideato install a secondary service lightningarrestor, such as G.E. Model9L15CCB007, called a Home LightningProtector, right at the service entrance.Otherwise, pull the plugs on allelectronic equipment when you'regoing to be gone for several days orwhen you're home and a thunderstormis building.""Do you think a high antenna towerinvites lightning damage to thehome ?",11N® °]ÌÌtoÌÌi¡-------___,`\Fig. 3. A metal antenna tower,properly grounded, provides a coneof for the house."Quite to the contrary, if the tower ismetal and properly grounded or hasthe metal mast properly grounded, itactually provides a cone of protectionas shown in Fig. 3. Note that theapex of the cone is at the top of thegrounded antenna, and the radius ofthe base is equal to the height of thetower. A direct strike of lightning toany object inside this cone is very unlikely.""All right, let's recapitulate: quizyour insurance agent and read yourpolicy carefully to see exactly whatkind of protection you have for yourelectronic equipment. To protect thatequipment, use lightning arrestors onall leads entering the house, includingthe power leads. Make good groundsand bond them together. Pull plugsduring storms or when you're going tobe away from home, and don't try tocon the service technician into helpingyou defraud the insurance company.If he goes along with that, he'llcheat you, too!"p73

It takes moreBell & Howell Schools introduces threefascinating learn -at -home programs featuringsome of the finest equipment available as your"teachers ". Choose the program you prefer -then mail card for free details today!Experience is the best teacher, without a doubt.And when it comes to learning electronics, we feel it'shands -on experience with state -of- the -art equipmentthat counts the most. That's why with Bell & HowellSchools'learn -at -home programs you work with some ofthe most up -to -date equipment. Equipment that's beingused today -and will be used tomorrow. So the skills andknowledge you acquire will be useful for years to come.Of course, with all our learn -at -home programsyou'll have plenty of lab manuals and basic principles towork with. And you'll also get exciting "teachers" to helpmake electronics come alive ...Lab Starter Kit gives you hands -on experiencewith the very first lesson.We get you started with the basics in an excitingway! At the very beginning you get a fully -assembledvolt -ohm meter as well as design panels, modularconnectors, experimental parts and battery. So you don'tjust read about electronics principles, you actually seethem at work!You build your own Electro -Lab "' electronicstraining system.Whatever program you choose, you getyour own home laboratory includingoscilloscope, digital multimeteranddesign console to give you actualexperience in wiring, soldering,assembling, testing, trouble- shootingand circuit analyzing.I. Learn new skills in the field of HomeEntertainment Electronics includingbuilding the new generation color TV .What better or more exciting wayto learn digital electronics! Once you havethe basics under your belt and get into colortheory and service, you'll build a 25" diagonalcolor TV and probe into the digital technologybehind digital channel numbers that flash on thescreen ... a digital clock that flashes the time tothe second and an automatic channel selector.learn aboutAs you put the set together, you'll discoverhow advanced integrated circuitry works, how totrouble -shoot it and much more. Upon completionof the program you'll have gained the specializedoccupational skills to service color TV's plus theprinciples that you can apply to repair a variety ofhome electronic equipment. And you'll have thefoundation to understand and work with new productapplications as they're developed, too!Il. Use professional communications equipment asyou delve into Communication Electronics .Here's how to pick up skills in the vital fieldof two -way radio, widely used in public safety, marine,industrial and transportation areas. Bell & HowellSchools Communication Electronics Program canhelp prepare you for the FCC licensing exam, rightthrough to 1st class radiotelephone operator. Andteach you skills in two -way radio, radar or commercialbroadcasting.For a refundable deposit, you get to use thespecial two -way radio equipment labfeaturing an FM transceiver,`'frequency meter, and \modulation meter. Allregular, first -rate commercialgrade test equipment.OP+'Electro- Lab" is a registered trademark of the Bell &Howell Company.Simulated TV Picture /Test Patternthan books toelectronics.Digital Trainer helps you learn the latest inintegrated circuits so you'll have a solid background inIndustrial Digital Electronics.modern digital electronics and its applications to industry.Digital technology is setting new standardsof accuracy and beginning a revolution inindustry.For example, more precisecontrol inrefining, manufacturing plants, foodprocessing and transportation.And now you can learnabout this technology withBell & Howell Schools' uniqueDigital Trainer. You'll analyze andexperiment with various types ofiyyp\/7 - uii////////'`,You study at home in your spare time ...with help as close as the telephone.Because these arehome study programs, youcan learn electronics without missing aday of work or a single paycheck.You study at your convenience -without being a classroomcaptive. If you ever have anyquestions, you can callour toll -free number for help.You can also meet and talk shopwith fellow students and instructors at "help sessions" held in50 cities at various times throughout the year.Bell & Howell Schools tries to give you morepersonal attention than any other learn -athomeprogram.Decide which exciting programyou're interested in ...you can checkmore than one. Then mail postage -paid card today for freeinformation -no obligation!Taken for vocational purposes, these coursesare approved by the state approval agency forVeterans' Benefits. Please check box on cardfor free information. Naturally, we cannot offerassurance of income opportunities.1. Power Output Meter 2. Design Console 3. ModulationMeter 4. Digital Multimeter 5. TriggeredSweep Oscilloscope 6. Lab Starter KitMultimeter 7. Frequency Meter 8. FMTransceiver 9. 25" Diagonal ColorTV 10. Alignment Generator1 1. Lesson Tape Player12. Digital TrainerÏrsè7248 2as been removed, please write to:An Electronics Home Study SchoolDeVRV IOSTITUTE OF TECHOOLOGVORE of THEBELL E; HOWELL SCHOOLS4141 Belmont. Chicago, Illinois 6064174POPULAR ELECTRONICSJANUARY 197577

irmiiiffiRrfilitProductTest ReportsTECHNICS BY PANASONIC MODEL T -200 SPEAKER SYSTEM(A Hirsch -Houck Labs Report)Compact, inexpensive system with room- filling sound.THE Technics Model T -200 is theleast expensive of a new seriesof loudspeaker systems fromPanasonic. It is a compact system thatmeasures 21 3/4 in. by 12 in. by 101/2 in.deep (55.2 x 30.5 x 26.7 cm) andweighs slightly less than 30 Ib (13.6kg). The oiled walnut cabinet contrastswith an attractive sculptured,acoustically transparent grille that isavailable in either blue or brown.The two -way system contains a10 -in. (25.4 -cm) acoustic -suspensionwoofer that crosses over at 1800 Hz toa 13/4 -in. (4.45 -cm) cone -type tweeter.The rated dispersion angle of thetweeter is 120° in both the horizontaland vertical planes. A switch is providedon the rear of the cabinet topermit the tweeter level to be set fornormal or 3 dB attenuation. (Flattestoverall response is obtained with maximumtweeter output.) The system hasa rated nominal impedance of 8 ohms.The retail price of the TechnicsModel T -200 speaker system is $99.95.Laboratory Measurements. Theresponse of the speaker system wasmeasured in a "normal" listeningroom by a method that yields a good78approximation of its total energy outputover the frequency range. Averagingand warble -tone measurementswere used to minimize the effects ofstanding waves. At frequencies lowerthan about 300 Hz, close microphonespacing was used, and the two testcurves obtained were joined togetherto provide a composite frequency -response curve.The response of the woofer wasnotably smooth, with a resonant peakof about 3.5 dB at 75 Hz and no sign ofirregularity up to several hundredhertz. The tweeter also had a ratherflat response curve (although it isnormal to find some irregularity athigh frequencies with the measurementmethods we used). Its output felloff smoothly at frequencies beyond10,000 Hz, with no sign of a peakthroughout its entire range. The overallresponse was a very good ±4 dBfrom 45 Hz to 14,000 Hz.The bass distortion at a constant1 -watt drive level was between 3% and5% from 100 Hz to 60 Hz. When we520RIB=varied the drive level to maintain aconstant 90 -dB sound -pressure level(SPL) at a di t a n ce of 1 meter m ee rfr from o thewoofer, the distortion was somewhathigher than we have measured onsome other speakers of the same size,but it was not audible on programmaterial.The tone -burst response was fairlygood. There were no signs of severeringing or generation of spurious frequenciesthroughout the operatingrange of the system. Efficiency wasmoderately low, as would be expectedof an acoustic -suspension design. Aninput of 1 watt in the midrange produceda 90 -dB SPL at a 1 -meter distance.This corresponds to about80 -dB SPL in the normal listening areaof a typical room, which is about asloud as most people would care to listento music in their homes.The electrical impedance of the systemwas 5 ohms at 20 HZ and between100 and 200 Hz. It peaked at 18 ohms atthe 62 -Hz bass resonance point. Atfrequencies higher than 1000 Hz, theimpedance was typically 15 to 18ohms.User Comment. The general shapeof the measured response curve forthe T -200 was confirmed by our simulatedlive- versus -recorded listeningtest in which the T -200 was used toimitate the sound of a specially recordedprogram played through a referencespeaker, our "live" orchestra.The T -200's midrange and highs werevirtually perfect, but there was aslightly full quality in the lower midrangeand upper bass range. This appearedto correspond with the facts:i iiik:im t:f?m1ai_E----_-_.c:::-R= ymMine gl_.., :llióáiiö=tJ :HIM: i ú: í7iM. u9E:...-:=R G=.:.1q(n?GiIG;i)Glái'IEGIF.GGORCtffEGlEá áili=. 111G1GaN EERM!!ENiGlE®®GIi:::: i_álIfigieltiaINIPERNIEWR®!®MMITORI'7°7.- ImEgliNmEl!"i' U G il úlçl4M GGIlGi®IGGGr ihryi1.78'®i8 á9i IM: ti Üli l°N F i- '= .2 e 0E=1mEf iúúiu má MINIM-TONE BURST -¡r1;4!ss:=4i1 JdGMGGINAE'GGGRE®GIgiP"=lGy_sMñm"i®niIi mil®fféEMBILTúi $1m1ßümmM®®áepMúI ïPall3-3'1Awiti oámGimiqu99effliGüi ;liibliGiéglii=.giiäe4E n5asaiiaÇ==aidRraifgá-lrIti916_é_t=3iiilgiiiiiriiilBilti:m,rtiRlP .,.. -a2i.raesiii iiè:üii'ii::i"!.':.:in!'ÉdkRáëxá:1É ié ix2!:aÿáráJi _-e_MCOMPOS 7ENFREO RESPONSE 1 Eibiiil®®ii1P_y{11®®1yy9I9®I9leAásiiilllli!:1::Y11i9ñddlla1191S1ii2iisáFiGa ::ta" t. '`.. u:.91..:'' »nl__ _ i=13ië;:y;?:á5ii s==aäiim1 m._._ asx7»_xmttxiñ.l ==16i iii' a i- s^::u°i^INllmiii "iSa:lai c9gGxE!..:e -a°I`i? __:_ai;a...:üGG..NIiGGiip --iili.liilmit:Bi:m::m:__e:esí.i_ : tv:t.xa a20 50 100 200 500 IkFREQUENCY -Hz2k Sk 10k 20k300 Hz 1800 Hz 7000 HzPOPULAR ELECTRONICS503020ó 10Is543W"i1ái ii iia i Rl1ii11=Eilill=iíIB@'aiiiiiüJB!i L.=i iäiï r ::_: x:"=___»,:r _.:. _ sMinii .m-ás:m pBállllaii!ái -=-aivaJl9. BM in :;;% +iiía2=:áiiá3li fi, Li :.-:ii m!)më FGiialill-._ppG1:;iifäigQ ill I,)Irsaiieaiar: _HIN i': E-:9eaa:.s aEI T iU I®® :::ssi:o:r.= ::- atgllii 9 yB5éaGilli(Iliii151N1:,° _ 9i átl161ilaatöH..,,i r- PiI91NlI uyE u= e=e=:::: '- viaía:ya:..ss»diliL9Eil#i:uNGiiIUIUIUÌ_:'s_-__--ss s=a11 ll a==a:bím+i99!iiiiC_11:.Y...s:Ei'1'1t_ Ltmtl9@i-::-_._iaL 1iiilLaí Á1 'iLO lIIilless ::ë:; p9Ril°I.» HiUi .áal! »._ s:sslx osa m:i8iilálimBi "- -- = iliii i áx-!aÉ ili_ sRE zxa:-asi:Brïi NI.UM::.: M3°_?énii(iiia»'iill IÏíiililiiRIM:i :: i EmaRineiam6ss_-::.I B iM 3=$: Eli :Hui Ilk 8191Ny.a!3s.ssan:RO1áss eM::ci9ElR-- IIMI)MNEGlmili°z i E Pili Ii.'i'1liFff.mz;;EC :'3ìit:::....? aaNHi:ßii 8i TECUU1cs T-2DD lem::3s:sti ir8fissus 6.1 á's=_Y._.ii'HI gokóáám°`r:iiiiiiisiaiiiabiláilliliiiiiN=iMIiEIN6sá6é sii'siaalirssi:ilR:.IMPEDANCEMIiifiralilllilitiaaiUiamlmiriEi=1Osill iaNml' =::Emba.5:.=_2:11ffniai=-- :rma I 91 0 m=111iss x.:n3 swnllBEe 1BE'N Vii LeE_ N.s__._l===: ::_ , .w1:that the average woofer level was afew decibels higher than was the averagetweeter level.When a 3- to 4 -dB attenuation (a00FREQUENCY (Hz).. -o 10000"shelf" response cut) was applied atfrequencies below 1000 Hz with anoctave -band equalizer, the speakersystem did a near -perfect job of imita-PIONEER MODEL RT -1011L STEREO TAPE RECORDER(A Hirsch -Houck Labs Report)Logic -controlled recorder handles 101/2-inch reels.THE U.S. Pioneer ElectronicsModel RT -1011 L stereo tape recorderfeatures three motors, threeheads, solenoid- operated transport,and 71/2 and 33/4 ips (19.05 and 9.53cm /s) operating speeds. This quarter -track recorder is designed to accommodatetape reels measuring up to101/2 in. (26.7 cm) in diameter. Thetransport is "logic controlled" so thatany operating mode or speed can beselected from any other without havingto first press the STOP button. Yet,the tape is fully protected againstbreakage and spilling.General Description. The recorder'stape loading procedure is simplifiedby a guide roller arm that locks outof the way when it is moved to its limitso that the tape takes a straight -linepath across the heads, over the capstan,and over a tensioning arm as itgoes to the take -up reel. The tensioningarm also serves as an automaticJANUARY 1975shut -off switch in the event of tapebreakage and when the tape runs out.Two large illuminated meters indicateboth recording and playbacklevels. The meters monitor the lineoutputs so that the playback indicationsvary with the setting of theplayback level controls. Locatedabove the meters is a red light thatcomes on whenever one or bothchannels is set to the RECORD mode.Below each meter is a standard jackfor 600- to 50,000 -ohm dynamic microphones.Locking pushbutton switches controlac power, tape tensioning for 7 -in.(17.8 -cm) and 101/2-in. (26.7 -cm) tapereels, and tape speed. Other pushbuttonsare labeled REC, PLAY, REWIND, FASTFORWARD, and STOP. For easy identification,the REC button is red, while theSTOP button is larger than the others.Although the pushbuttons energizesolenoids, they are designed tomechanically lock into position topermit the recorder to be set up inadvance for recording. When linepower is later applied by an externalclock timer, the deck goes directly intoits recording mode.Five lever switches supplement thepushbuttons. Two place the channelsindividually into the recording modewhen the REC button is pressed. This isa safety feature that prevents accidentaltape erasure. lt also serves as ameans of recording on one channelwhile playing back through the otherfor echo and sound -on -sound (the latterrequiring external patching).Two more levers provide excep-ting the original sound in an A -B corn -parison. The highs were obviouslypeak -free and very dispersed.Listening to this speaker system,one is apt to find it difficult to believethat the sound is coming from an inexpensivecompact system. It gives aroom -filling sound suggestive of amuch larger system and provides exceptionallygood musical balance andoverall smoothness. The T -200 illustratesmost effectively how the propercombination of conventional driversand crossover components by aknówledgeable designer can producea total sound character that is greaterthan the sum of its parts.CIRCLE NO. 65 ON READER SERVICE CARDtional flexibility in adapting the recorderto any type of tape. Theyseparately control recording biasand equalization. Each has positionsfor STD (standard) and LH (lownoise /high- output) tape formulations.A table in the comprehensive instructionmanual provided with the recordersuggests switch setting combinationsfor many popular tapes. Alternatively,optimum conditions can be determinedby recording and listening.The last lever switch connects theline outputs to either the source(input) signal or to the playbackamplifier's outputs.Concentric control knobs are providedfor independently adjusting therecording levels in the two channels.One pair of controls is for the microphoneinputs, while the other is forthe line inputs. A third pair of concentriccontrols permits the playbacklevel to be adjusted in each channel.A stereo headphone jack is locatedon the recorder's front panel. The lineinputs and outputs and a DIN socketthat repeats the two are located on therear of the recorder.The recorder can be operated verticallyor horizontally. It measures 17 in.high by 16 7/8 in. wide by 8 15/16 in.deep (43.2 x 42.9 x 22.9 cm) andweighs 49 Ib (22.3 kg). It comes withwalnut side panels, a 101 /2 -in. metalreel, and two reel -hub adapters forprofessional -size reels with largecenter holes.The retail price of the Pioneer ModelRT -1011 L stereo tape recorder is$599.95.Laboratory Measurements. UsingAmpex test tapes, we found theplayback equalization of the tape re-79

5dBa 8'rä:.ud i :dial dap11111 wzrar. iiiñá:aaau: earQzg3ai r:-¡AA ä1Iî!9 ñiyy-i: LW . m,a! n: 9919 ÑI9l lli-zl 9 99p re a.éRECOMPRITAIMMONSE :.ii,çSgcunlala iiç I I :...nl a 9. ipis.!g8i9 aie r._,. g!á rcx!-: ima, A96fliÑpeeOinaii ri :06 ra!S!_ a.: m:°6.di91 eN9$ell 19lII99aiam5am kn.aums:ae r. ...LEMIMMIREMORN mg 1E18 prdeotmuaa-er.:nam:mnamoñigleu.9mta:=áeso:o_om an::..corder to be very accurate at bothspeeds. It was within ±0.5 dB from 50Hz to 15,000 Hz at 71/2 ips and within±0.8 dB from 50 Hz to 7500 Hz at 3 3/4ips. (These are the frequency limits ofthe test tapes.)We used 3M No. 207 tape for thebalance of our tests. We measured therecord /playback response with all fourcombinations of switch settings. Althoughthe differences were slight, weconcluded that the LH bias and STDequalization settings yielded the flattestoverall frequency response.Using a -20-dB recording level at 33/4ips, the overall response was within±2.5 dB from 20 Hz to 13,500 Hz. At a0 -dB recording level, tape saturation(expected at this speed) caused asharp drop -off in response beyond7000 Hz. At 71/2 ips, the response at the-20 dB level was a very flat 2.5 dB from20 Hz to 24,500 Hz. It was within -±1 dBfrom 25 Hz to 21,000 Hz. Saturationwas less of a problem at higher recordinglevels at 71/2 ips. Hence, the 0 -dBresponse did not begin to fall off appreciablyuntil we reached 12,000 Hz.The line inputs required 43 mV for a0 -dB recording level. This produced amaximum playback output of 0.5 volt.The microphone sensitivity was 0.18mV for 0 dB, while the amplifiers over-FREQUENCY (Hz)60 00 00000loaded at 70 mV. This should be quiteadequate for most recording situations.A standard Dolby level tape playedback with a full -scale +3 -dB meter indication.The meters were somewhatslower in responding than are true VUmeters. They indicated 65% of theirsteady -state values on 0.3- secondtone bursts as compared to 99% for atrue VU meter.At a 0 -dB recording level, theplayback distortion was 1.0% at 71/2 ipsand 1.2% at 33/4 ips. To reach the standard3% reference distortion level, itwas necessary to record at +12 dB (faroff the meter scales) at either tapespeed. Referred to this level, the unweightednoise was -62 dB at 7V2 ips.With IEC A weighting for better correlationwith subjective effects, thenoise was -70.5 dB. It is interesting tonote that the S/N ratio at 33/4 ips wasonly 0.5 dB lower than at 71/2 ips. Atmaximum gain through the microphoneinputs, the noise level increasedby a negligible 3 dB.The tape speeds were 0.4% fast at71/2 ips and 0.4% at 33/4 ips. In fast forwardand rewind, an 1800 -ft (550 -m)tape passed in 84 seconds. The unweightedrms flutter was 0.12% at 71/2ips and 0.16% at 33/4 ips. To our sur-HEWLETT -PACKARD MODEL 5381A FREQUENCY COUNTERSeven -digit, laboratory-grade instrument operates to 80 MHz7=1.013'-:''_: tWITH the increasing number offrequency sensitive circuits inmodern electronic systems -filters instereo receivers and speaker crossovers;SSB, RTTY, and SSTV filters inham gear; digital systems in frequencysynthesizers and calculators -a goodfrequency counter is an importantitem to have on the electronics workbench.A frequency counter is essentialfor checking the accuracy of dialson r -f and a -f signal generators.Though they are usually "within theball park," dial accuracy and resetabil-prise, the flutter was reduced whenthe guide roller arm was locked in itsloading position. (It normally plays animportant part in reducing flutter.) Theflutter measurements were then 0.08%and 0.12% respectively. Wow was theresidual of the test tapes, measuring0.01% to 0.02 ° /e.The tape transport operatedsmoothly and appeared to be foolproof.When going from either fastspeed to PLAY, the tape came to a stopin about a second and paused for 2 or3 seconds before going into play. Themanual explains how the PAUSE controlcan be used to eliminate even thissmall delay if desired.The headphone outputs had verygood volume levels, even with 200 -ohm high- impedance phones.User Comment. Despite an ability toaccommodate 101/2 -in. reels, this isvery much a home tape recorder -anoutstandingly fine one. In ease of loadingand handling, it is about as simpleand straightforward as any machinewe have used. Its frequency response,distortion, and noise levels are amongthe best we have measured and woulddo justice in most respects to any professionalrecorder.Due to the calibration of the deck'smeters, it is eminently practical tomaintain average music recordinglevels near the 0 -dB mark. The meterpointers can be permitted to swing tofull -scale and beyond on peaks withoutserious risk of over -recording.Needless to say, the deck did a flawlessjob of recording from phonographand tuner sources as well as ofplaying back commercially recordedtapes. At a surprisingly reasonableprice, the Pioneer Model RT -1011 L offersan impressive combination ofhigh performance and operating versatility.CIRCLE NO. 66 ON READER SERVICE CARDity are more critical when complex filtersare involved since they don't workproperly unless they are tuned "on thehead."Although there are many reliablefrequency counters, it is nice to seethat one more big name (Hewlett -Packard) has entered the relativelylow -cost market with their Model5381A Frequency Counter ($249).This 7 -digit (LED) laboratory -gradeinstrument has a frequency range of10 Hz to 80 MHz (which means it canbe used in the CB and ham ranges).Sensitivity is 25 mV up to 20 MHz and50 mV to 80 MHz. Accuracy is-±1 countplus or minus the time -base accuracy.The time base uses a 1 -MHz crystalthat ages less than 0.3 ppm /month,±10 ppm from 0° to 40 °C, and ±1 ppmfor a-10% line voltage variation.Gate times can be selected manuallyand the resolution is 10 Hz at the0.1- second gate time, 1 Hz at the1- second gate time and 0.1 Hz at the10- second gate time. The input impedanceis 1 megohm shunted by 50 pF.Even at the most sensitive settings, theinput to the counter will handle up to200 volts (peaks ac plus dc) withoutharm.Physically, the 5381A is quite pleasingin appearance, with a clean, unclutteredlook. It is 3.5 ". high, 6.25"TRAM DIAMOND 40 AM CB TRANSCEIVERHas output circuit protection, SWR bridge and noise blankerTHE Tram Diamond 40 is a 23-channel crystal- synthesizedmobile transceiver designed for AMoperation on the Citizens Band.Among its special features are amicrophone -gain control, final -amplifier protection circuitry, built -inSWR bridge, switchable noise blanker(in addition to the usual AM -type noiselimiter), and a theft -deterrent mobilemounting bracket. An edgewise metermovement indicates relative signalstrength on receive and relative outputpower or SWR on transmit. Alsoincluded are the usual adjustablesquelch, Delta tune, public- addressfacility, and detachable microphone.The transmitter operates at full legalpower when the transceiver is connectedto a nominal 13.8 -volt dc powersource. The power source can beeither a positive- or a negative -groundsystem. Reverse -polarity protection isprovided in either case. Stability ofcritical circuits under varying sourcevoltages is assured by means of abuilt -in electronic voltage regulator.The transceiver measures 8 in. by63/4 in. by 21/2 in. (20.3 x 17.1 x 6.4 cm)wide, and 9.75" deep. It weighs 4.75 lband has a built -in tilt stand.User Comment. We had the opportunityof using the 5381A for severalweeks on a variety of electronicequipment. After aligning a number ofSCA traps and half a dozen or so filtersin SSB and SSTV rigs, and checking anumber of countdown circuits in digitalprojects, we really got to like thelook of the seven -digit, easy -to -readdisplay. In the MHz mode, reading thevalue down to three decimal placeswas easy, while in the Hz mode, resolutionwas 0.1 Hz.The 5381A was in regular use in theshop even through the so- called"brownout" days when the power linehad considerable variations. We didand weighs 6 pounds (2.7 kg). It retailsfor $209.95.The Receiver. According to ourtests, the double -tuned receiver hasexcellent sensitivity and selectivity.The sensitivity measured 0.3 µV for 10dB (S + N) /N at 30% modulation and1000 Hz. Adjacent -channel rejectionwas nominally 60 dB, while goodcommunication quality was maintainedwith a 6 -dB overall bandpass of450 to 2400 Hz.The bipolar r -f input amplifier isequipped with shunt diodes that serveas protection against overloads. Thefirst conversion to a 10.0- to 10.04 -MHz i -f is accomplished with the aid ofa FET mixer. A bipolar- transistormixer is used for the second conversionto a 455 -kHz i -f. Selectivity is obtainedby using a ceramic -filter bypassat the emitter of the second mixer anda ceramic filter at the input of the two -stage 455 -kHz i -f section.Application of dual agc voltages tothe r -f stage, plus a single loop to thesecond mixer, provides an exceptionallyflat output response level. Only a4 -dB output change occurred with a20 -dB input signal variation (at 1 -10.iV). A 3 -dB change occurred with a60 -dB input change (at 10- 10,000 MV),and a 6 -dB change with an input excursionof 80 dB (at 10- 100,000 11V).Approximately 50 1.1V of input signalwas needed to register S9 on themeter.Other measurements indicated an80 -dB rejection of the primary imagenot have to worry about the accuratesettings on the various frequencygenerators since the excellent accuracyof the 5381A, even with 5% to 8%power reductions, enabled us to makecritical adjustments.A number of CB rigs have beenchecked and aligned with each other,after which, communication betweenunits was improved due to the closerr -f alignment. The tone -alert accessorieswere also re- aligned so that thesystems worked as they did whenbrand new.For use at even higher frequencies,Hewlett- Packard also has a Model5382A, a 225 -MHz version, whichcosts $450.CIRCLE NO. 67 ON READER SERVICE CARDand 70 and 90 dB i -f signal rejection at10 -10.04 MHz and 455 kHz, respectively.Spurious -signal rejection measured55 dB minimum.The noise blanker is a parallel -gatesetup in which an IC is used at thefront end and for gating the output ofthe second mixer. It can be turned onand off while simultaneously shiftingin and out of the circuit a series -gatetype a -f automatic noise limiter (an!).This noise -reducing setup proved tobe extremely effective. It attenuatednoise pulses of 30 to 40 dB above a0.25 pV signal down to near inaudibilityin the presence of the signal. Its usedrops the overall gain on weak signalsby 4 to 6 dB, but the sensitivity -versus-S/N ratio is unaffected.(A noise limiter is simply an audio -frequency signal peak clipper. Usuallyset to provide 100% modulation, itclips any signal level that exceeds thatrequired for full modulation. Theblanker, on the other hand, interruptsthe r -f signal path momentarily duringhigh -level noise pulses ahead of theselectivity circuits. A limiter is a simpledevice that operates well enough, butbecause of its clipping action cancause a -f signal distortion when clippingtakes place. The blanker is moresophisticated, operating only for shortnoise -signal durations. Because it interruptsthe signal path, it is not distortionproducing.)The push -pull class -B output amplifieris driven by an IC. In our tests, itdelivered a 3.5 -watt output at 5.5 %distortionat the onset of clipping with a1000 -Hz test signal. With clipping, theoutput was 4.5 watts at 10% distortion.A thermistor- compensated squelch80POPULAR ELECTRONICSJANUARY 197581

was adjustable for thresholds of from0.25 to 300 µV.Frequency Synthesizer. Thecrystal frequency synthesizer in theDiamond 40 employs six crystals in the16.965- to 17.215 -MHz range. Four ofthe crystals are cut for the 9.545- to9.585 -MHz range for the receiver andfour are cut for the 10.0- to 10.04 -MHzrange for the transmitter. Duringtransmit, the frequency tolerance heldto within 440 Hz on any channel.The Delta -tune circuit for the receiveris detented at its center position,allowing the CB'erto "feel" whenit is set to the middle of the channel.The Transmitter. A triple -tunedbandpass -coupling network minimizesspurious responses from thesynthesizer mixer for the transmitter.The r -f power output amplifier employsa triple -tuned output- matchingsection. Collector -modulation of thedriver stage and power amplifier isaccomplished with the receiver's a -fsetup plus a speech amplifier for themike. (The latter is automaticallyswitched in for this mode.)With operation from a 13.8 -voltsource the r -f carrier output measured4.5 watts. The distortion measured 9%at 100% modulation at 1000 Hz, andthe frequency response was 270 to2700 Hz at the 6 -dB points. Adjacent -channel splatter, using a 2500 -Hzstandard EIA test tone, was -50 dB.Advancing the mike gain control foran additional 6-dB input -signal level (apractice the operating manual advisesagainst) caused clipping and in-EDMUND SCIENTIFIC KIRLIAN ELECTROPHOTOGRAPHY KITE.vperimental photography provides fascinating results.Electrophotography kit is set up ontop of carton in which it is received.with electricityPHOTOGRAPHYgoes back to the 19th century.But it wasn't until Czechoslovakianresearchers in 1939 published "electrophotographs"of leaves displayingstrong corona patterns that some interestin the field emerged. It was theRussian scientists, the Kirlians, however,who truly developed the methodin depth over the years, creating awide range of patented apparatus foruse in various fields.Kirlian photography permits one toview brilliant emanations from organicor inorganic objects, made visiblephotographically only when thesubject is placed in a field of high -frequency electrical currents. Usingcolor film, the images are spectacular,revealing all colors, shades, patterns82and degrees of brilliance. Some observersdescribe it as a pulsing energysource. Scientific interest revolvesaround interpreting the corona or"bio- energy" force, which displayschanges as a result of anger, illness, orfear in a human; lack of water in aplant; etc.The Edmund Scientific Company's"Kirlian" Electrophotography Kit (No.71,938) at $49.95 uses the principledescribed, opening up a new world ofphotography for experimenters.What It Is. Edmund's "Kirlian"photography kit consists of a variablelow- voltage transformer; a high -voltage, high- frequency inductioncoil; metal electrode; glass plate;photo changing bag; and all neces-creased the adjacent -channel splatterto -40 dB. With speech at normal modulatinglevels, the splatter was somewhatless. Setting the gain control tothe point where the modulation startsto make the transmitter -on lamp blinkslightly will usually hold the modulationwithin acceptably safe limits.The fail -safe setup in the transmitterfunctions as follows: If the antennaline is badly mismatched to the transmitter,the resulting SWR will producea large reflected voltage from the SWRbridge. This voltage is then used todisable the transmitter drive and thusprotect the output transistor fromdamage under improper load conditions.This is a protective scheme wewould like to see more of in transmitters.CIRCLE NO. 68 ON READER SERVICE CARDsary lead wire. Calling it a kit is really amisnomer, as one does not truly"build" it. For example, the variablevoltage step -down transformer andthe high- frequency induction coil arefully assembled. What one does is setup the system from assembled components.The high -quality step -down transformer,which is plugged into a 117 -Vac source, provides output voltagesthat can be varied from three to eightvolts. It includes an on -off switch. Thehigh- frequency induction coil, whichis fed the step -down transformer's lowac voltage, converts the voltage to ahigh- frequency, high -voltage output.High frequencies are developed by aset of vibrating contacts that interruptthe input at a rapid rate. Though outputvoltage from the induction coil isvery high, the secondary's output currentis quite low, being limited by coresaturation. Nonetheless, great careshould be taken when operating thedevice to avoid a shock.Setting up the "Kirlian" kit is simpleenough. Assuming a suitable darkenedroom for photographic developingpurposes, here are the assemblysteps: The cardboard shipping containeris used as a support for settingup, folding one side's flaps inside andpoking a pencil -size hole in the closedbottom to pass the high -voltage lead.Placing the high -voltage inductioncoil inside the carton, the high -voltagelead is pulled through the hole so thatit protrudes from the carton. Now thecarton is resting on its open side, theclosed top acting as a platform withthe electrode lead protruding.The twin power leads of the induc-POPULAR ELECTRONICStion coil are brought out from the bottomedge of the carton and pluggedinto the jacks of the variable low -voltage step -down transformer that ispositioned outside the carton. Strippingabout one inch of insulation fromthe high -voltage lead protruding fromthe carton top, the lead is bent 90 de-Kirlian photograph of abegonia leaf showing thecorona around the edge.grees, with the excess wire pushedback into the carton. The square,metal electrode is then placed on topof the HV electrode lead and theperimeter of the metal is taped to thecarton with masking tape. Next, theglass dielectric plate is centered atopthe electrode and taped down.If a suitable darkroom is not available,the photo changing bag should beused. Here, a hole is poked throughthe bottom to accommodate thehigh -voltage lead. The lead plus componentson top are placed inside thebag, with the bag and its contents restingon the carton.Completing setup, the followingtests should be made before photographingan object. The stepdowntransformer control should be set toits maximum, eight volts. Poweringthe device, you should hear "buzzing"of the interrupter contacts of thehigh- frequency coil. Next, the user'shand should be placed on the glassdielectric plate. The result should be aslight tingling sensation due tocapacitive coupling of the high -frequency current. In the dark, acorona discharge should be seen fromyour hand; maybe, a crackling soundheard. (Caution: Do not operateequipment if the glass dielectric plateis damaged; limit skin area exposuresto about one minute per day; use in awell ventilated area to prevent ozonebuildup; use a pair of glass -lensedsunglasses when viewing the coronaso that shortwave ultraviolet raysJANUARY 1975won't cause eye irritation; do not operatein the presence of anyone withimplanted devices such as heart pacersor around children or anyone notfamiliar with normal electrical safetyprecautions.)Either 35 -mm film or Polaroid 4 x 5sheet film type 58, may be used. Thefilm is placed directly on the glassdielectric plate, centering it over themetal electrode under the glass. Theemulsion side is placed face up. Anobject to be photographed "Kirlian"style is placed directly on the film. Forsmall objects, such as a coin, one'sfinger is placed on the object to providea ground.Comments. Setting up the EdmundKirlian Photography Kit was an easyjob. But in our haste we did not followdirections to tape down the glassdielectric. After using the system awhile, the glass moved, which allowedan associate to be jolted by a discharge.With the glass covering themetal electrode, however, only a mildtingling sensation was felt. Followingthis, we taped down the hot lead andwiped the glass on both sides to besure that moisture and dirt would notprovide an electrical path.We used black- and -white sheet film(ASA 32), taping it to the glass. However,35 -mm film, black- and -white orcolor, can be used. For the lattar, thecassette should be taped close to theedge of the glass, securing the leaderto a bulk -film reloading 35 mm cassette,which is taped to the oppositeend of the glass. Using a 3/8" wooddowel as a handle, tapering the end tofit the bulk -film cassette, five clockwiseturns of the spool (done in thedark) will withdraw sufficient unexposedfilm.A user must experiment with exposure.Recommendations by the manufacturerare a fair guide, but best exposurevaries due to humidity, filmdampness, object density, etc. Typicalexposures will be 12 to 15 secondswhen the voltage control is set ateight. We started at six volts, feelingthat there's more control over exposureif time is a bit longer.There's no doubt that "Kirlian"photography is fun. You'll be amazedat the results, especially with colorfilm. Edmund Scientific also has a$9.95 starter kit and a more expensive"professional" kit. The former uses apiezoelectric demonstrator.CIRCLE NO. 69 ON READER SERVICE CARD346ÓnSaveInstruments,BurglarotiAlarms, veobJ1Electrbonics!The more you know aboutelectronics, the more you'llappreciate EICO. We have a widerange of products for you tochoose from, each designed toprovide you with the mostpleasure and quality performancefor your money. The fact thatmore than 3 million EICO productsare in use attests to their qualityand performance."Build-ft-Yourself" and saveup to 50% with our famouselectronic kits.For latest EICO Catalog on TestInstruments, Automotive and HobbyElectronics, Eicocraft Project kits,Burglar -Fire Alarm Systems and nameof nearest EICO Distributor, check readerservice card or send 500 for fast firstclass mail service.EICO -283 Malta Street,Brooklyn, N.Y. 11207Leadership in creative electronicssince 1945.E/CO1-7CIRCLE NO. 14 ON READER SERVICE CARD83

From Cleveland Institute of Electronicslearn by doing!You get your own 161 -piece electronics laboratory...with authentic electronic components used by industry!Perform more than 200 exciting experimentswith CIE's fascinating ELECTRONICSLABORATORY PROGRAM!POPULAR ELECTRONICSYou learn how to construct circuits andconnect them with a soldering iron, whichis part of your CIE laboratory equipment.This "hands on" experience is extremelyvaluable in applying what you learn.Testing and troubleshooting are an importantpart of your learning experience.Included in your laboratory is a precision"multimeter" to diagnose electrical andelectronic troubles quickly and accurately.Modern space -age components like thisIC (integrated circuit) are professionalquality and can be used again and againin many of your projects. Lesson by lesson,piece by piece your knowledge grows!Prepare now for a high income career in Electronics...the Science of the Seventies.Electronic miracles are changing you complete our Laboratory Course, facturing, Inc., Scottsbluff, Nebraska,today's world with breathtaking which provides FCC License prep- moved from TV repairman to labspeed.aration, you'll be able to pass your technician to radio station chiefAnd with this growth in electronics FCC exam or be entitled to a full engineer to manufacturer of electechnologyhas come a brand new refund of all tuition paid. This war- tronic equipment with annual salesneed ... a demand for thousands ofelectronics technicians, trained intheory and practice to build theproducts, operate them and servicethem during the Seventies.Don't just wait for something to"happen" in your present job. Getready now for a career you'll reallyenjoy with a good income and plentyof opportunity for advancement.Experience with experimentsis your best teacher"Hands on" experience helps to reinforcebasic theory. When youlearn by doing, you discover the"how" as well as the "why." You'llfind out for yourself the right way aswell as the wrong way to use electroniccomponents. How to constructyour own circuits, to discover troublespots and learn how to fix them. Andwith CIE's special Auto -Programmed®Lessons, you learn faster and easierthan you'd believe possible.CIE's fascinating course, ElectronicsTechnology with Laboratory,teaches you Electronics by makingit work before your eyes. And you doit yourself, with your own hands.Importance of FCC Licenseand our Money -Back WarrantyMany important jobs require an FCCLicense and you must pass a Governmentlicensing exam to get one.But, a recent survey of 787 CIEgraduates reveals that better than 9out of 10 CIE grads passed the FCCLicense exam.That's why we can offer this famousMoney -Back Warranty: whenJANUARY 1975ranty is valid during the completion of more than $500,000. Ed Dulaneytime allowed for your course. says, "While studying with CIE, IYou get your FCC License - or learned the electronics theories thatyour money back!made my present business possible."Marvin Hutchens, Woodbridge,Virginia, says: "I was surprised at therelevancy of the CIE course to actualworking conditions. I'm now servicingtwo -way radio systems in theGreater Washington area. My earn-You'll have high payingjob opportunitiesElectronics is still young and growing.In nearly every one of the new excitingfields of the Seventies you findelectronics skills and knowledge arein demand. Computers and data processing.Air traffic control. Medicaltechnology. Pollution control. Broadcastingand communications. With aCIE Diploma and an FCC Licenseyou can choose the career field youwant ... work for a big corporation, asmall company or even go into businessfor yourself.Here's how two outstanding CIEstudents carved out new careers:After his CIE training, Edward J.Dulaney, President of D & A Manu-.V.)\ApprovedunderG.I. BillAll CIE careercourses are approvedfor educationalbenefitsunder the G.I. Bill.If you are a Veteranor in service now,check box for G.I.Bill information.ings have increased $3,000. I boughta new home for my family and I feelmore financially secure than everbefore."Send now for 2 FREE BOOKSMail the reply card or coupon for ourschool catalog plus a special bookon how to get your FCC License. Foryour convenience, we will try to havea representative call. If coupon ismissing, write: Cleveland Institute ofElectronics, Inc., 1776 E. 17th St.,Cleveland, Ohio 44114. Do it now!4&C' E Cleveland Institute of Electronics, Inc.1775 East 17th Street, Cleveland, Ohio 44114Accredited Member National Home Study CouncilPlease send me your two FREE books:1. Your illustrated school catalog, "Succeed in Electronics."2. Your book, "How to Get a Commercial FCC License."am especially interested in: Electronics Technology with LaboratoryElectronics TechnologyIndustrial ElectronicsElectronic CommunicationsFirst Class FCC LicenseBroadcast EngineeringElectronics EngineeringNameAddressCIRCLE NO. 9 ON READER SERVICE CARD(PLEASE PRINT)City State lipVeterans and Servicemen: Check here for G.I. Bill information. PE -72Age87

haveiEa/A1__.,77rif Solid StateLOOKING INTO THE CRYSTAL BALLI F YOU'VE been a regular reader of this column, youII know that I enjoy playing an annual guessing game withthe electronics industry, predicting what new semiconductorproducts or technological advances will be introducedeach year. For nearly two decades, my predictions haveproven accurate better than 90% of the time. Because ofthis record, some have accused me of being an inspiredprophet. Not so!Actually, my annual predictions are based on an extrapolationof known developments in the industry. A "guesstimate"of where present trends are leading and what couldbe done with present technology. The method is similar tothat used by science -fiction authors, but extended to theimmediate, rather than the distant future.Sometimes, my predictions have proven early by a yearor so- simple examples of over -optimism and expectationsthat the industry would move faster in some areasthan in others. Just as often, however, I've goofed in theopposite direction, predicting a new development which isannounced before the colum appears in print.Let's see how I fared with the predictions made inJanuary, 1974. As you may recall, I predicted:A substantial drop in the prices of digital electronicwatches from the present hundreds of dollars. Score onefor the OM! Surprising just about everyone and catchingsome manufacturers with their inventories up, NationalSemiconductor Corporation's Novus Consumer ProductsDivision (1177 Kern Avenue, Sunnyvale, CA 94086) introduceda line of six digital electronic watches in early fallwith a list price on one model of only $125.00Comparable reductions in the prices of digital electronicclocks. Score another! At the same time that Novus announcedits new low- priced electronic watches, it alsoannounced a line of three digital electronic alarm clocks.The lowest priced model in the line lists at $34.95!LED's at prices comparable to those of miniature incandescentlamps in small quantities. Another home run(bull's -eye, or whatever)! Recent advertisements in thesepages offered type MV50's at six for a dollar, MV5024equivalents at eight for a dollar, MV5222 equivalent greenLED's at five for a buck, and Mini -Red LED's similar to theMV50 at a whopping ten for a dollar.The introduction of control -function IC's as stock items.Chalk up another score! Space limitations prevent ourlisting all of the various control IC's now available throughmajor distributors, but two moderately priced types whichshould be of interest to serious experimenters are the88By Lou GarnerSGS -ATES L120 and L121 (SGS -ATES Semi -conductorCorp., 435 Newtonville Ave., Newtonville, MA 02160). Bothdevices are offered in 16 -pin DIP's, both are priced at $6.00each in unit quantities, and both are intended for controlfunctions in industrial and consumer applications. TheL120 is a Triac /SCR phase control and the L121 aTriac /SCR burst control.The development of one or more new solid -statetransducers. WOW! We really hit the jackpot on this one.Several manufacturers introduced new solid -state transducersduring 1974, with the National SemiconductorCorporation now offering so many types that it recentlypublished the industry's first catalog /handbook on pressureand temperature transducers. Entitled Transducers:Pressure and Temperature, the 160 -page volume is muchmore than a mere listing of device specifications and options.It covers general transduction theory as well as thetheory of operation of IC transducers in particular, andincludes a number of useful tables plus a lengthy glossaryof transduction- related terms. The book's applicationssection discusses automotive, medical, and audio uses,cable fault location, and even musical instruments, such asan electronic clarinet that comes on like a Sousaphone.Copies of the book are available without charge on letterheadrequest to the Marketing Services Department,National Semiconductor Corporation, 2900 SemiconductorDrive, Santa Clara, CA 95051.The introduction of low -cost (about $100) preprogrammedbusiness calculators. Another winner! Virtuallyall major calculator manufacturers have introduced inexpensivespecial purpose models. Casio, Inc. (ConsumerProducts Div., One World Trade Center, New York, N.Y.10048), for example, offers one model, the Mini Root,which can supply square roots at the touch of a button andwhich provides automatic percentages for figuring markupsand discounts, at a list price of only $54.95. The Cole -Parmer Instrument Co. (7425 North Oak Park Ave.,Chicago, IL 60648) offers a metric conversion computerwith full 5- function capability at a list price of only $84.50.And these are but a small sampling of the models introducedduring 1974!Digital electronic test instruments, such as VOM's andfrequency meters, at prices comparable to those of instrumentsusing moving -coil meter movements. Is thereany doubt?Development of a new semiconductor manufacturingtechnique or a refinement in current techniques which willPOPULAR ELECTRONICSimprove quality, increase yield rates, and lower costs. Iadmit to "hedging" slightly on this prediction, offering twoalternatives. However, fortunately for the OM, both optionswere fulfilled during 1974. Nearly every major semiconductormanufacturer was able to improve production techniquesto the point of boosting product quality while, at thesame time, lowering prices. In addition, several firms introducednew techniques. RCA, for example, introduced atechnological advance for the semiconductor industry bycombining MOS and bipolar devices -PMOS, bipolar andCOS /MOS-on a single chip. The first device offered basedon the new technology is the CA3130 operational amplifier.Supplied in an 8 -lead TO -5 package, the CA3130 featuresa gate -protected p- channel MOSFET input stage with anextremely high input impedance of 1.5 x 1012 ohms and acomplementary- symmetry (COS/MOS) output stage capableof swinging the output signal voltage to within a mere10 mV of either supply voltage terminal. In addition, thedevice offers a wide 15 -MHz bandwidth and has a sink andsource current capability of 20 mA. Short -circuit protected,the CA3130 has a broad range of applications,including ground- referenced single -supply and fastsample -hold amplifiers, long duration timers and mono -stables, high- input- impedance comparators and wide -band amplifiers, voltage -followers and regulators, peakdetectors, single -supply full -wave precision rectifiers, andphoto -diode sensor amplifiers.The announcement of an unusual new solid -statedevice. Another score! Not one, but several unusual newdevices were introduced during 1974, many of which werediscussed in these pages (including the CA3130). In makingthe original prediction, I suggested that one possibilitywas a special type of LED, speculating that it might havebilateral switch characteristics. In fact, a family of unusualnew LED's was introduced by Litronix, Inc. (19000 HomesteadRoad, Valico Park, Cupertino, CA 95014) -theRCL -200 series. These devices do not have switchingcharacteristics as we speculated, but do incorporate abuilt -in bipolar current -regulator IC, permitting their useon dc supply voltages of from 4.5 to 12.5 volts without anexternal current limiting resistor.Things to Come. Now for our predictions for 1975:A price break -through on solid -state imaging devices,possibly as a result of a new manufacturing technique. Ona long term -several year- basis, I anticipate that videocameras will one day be as compact as home moviecameras and, perhaps, priced in a comparable range.[Next month's issue will fulfill Lou Garner's prophecy-Ed.]The development of personal health monitors for patientssubject to sudden attacks or seizures. I envision adevice no larger than a hearing aid which would alert theuser in advance of a possible attack.Digital electronic watches in the range of $50 to $60. Atthe same time, I expect electronic watches in thehundred -dollar range to include a calendar feature, and,perhaps, even an integral alarm.A digital MPG (miles-per-gallon) meter for automotiveapplications. Such an instrument has been proposed but,as yet, is not in commerical production. I expect that it willbe introduced first as a custom add -on accessory for retrofitting,but will be offered later as an optional accessoryby one or more major manufacturers.A low -cost electronic calculator designed specificallyfor the children's market. As I visualize this product, it willJANUARY 1975LFind whatever circuityou need instantlyTHE LARGESTCOLLECTION EVEROver 3,600 circuit diagrams, completewith component values, in one handyvolume, all clearly indexed and cross -referenced for speedy answers to yourimmediate design needs.Whatever your project -a hi -fi system, a burglar alarm,a solid state metal detector, an automatic timer -youname it, you'll find the circuit that best meets yourneeds in this, the largest single -volume collection ofillustrated circuits ever to be published.131 CHAPTERS, each devoted to a particular type ofcircuit, present 3,600 individual circuits, all with essentialconstruction and adjustment details, design precautionsand other practical data. The advantages and disadvantagesof the various circuits are also given so you candecide quickly and easily what best meets your needsat the moment.FAST, EASY USE. The Index has over 10,000 entriesthat list -and cross -reference -circuits by all their differentnames, by performance parameters, by applications,and by a host of other relevant categories. Perfect forsuper -fast looking or leisurely leafing.SAMPLE CONTENTS quadraphonic circuits ... taperecorder circuits ... citizens band circuits ... measuringcircuits ... filter circuits ... amplifier circuitscode circuits ... telephone circuits . , . signalgenerator circuits ... flasher circuits ... switchingcircuits ... and thousands more!And in case you missed Markus' two previous circuitbooks, use the coupon below to order examinationcopies. 92,000 already sold. Absolutely no duplicationof circuits in these three volumes.SOURCEBOOK OF ELECTRONIC CIRCUITSBy John Markus 888 pp. 81/2" x 11" $23.503,000 different circuits with values and exact sourcecitations.ELECTRONIC CIRCUITS MANUALBy John Markus 892 pp. 81/2" x 11" $24.753,181 different circuits with values and exact sourcecitations.At your local bookstore or use coupon below for- - on - FREE 10 -DAY EXAMINATION - - - -McGraw -Hill Book CompanyII ,1221 Avenue of the Americas, New York, N.Y. 10020 I.Please send me the book(s) I checked below for a free 10 -dayexamination. In that time I will either remit the price, plus local tax,postage, and handling, or return the book(s) with no further obligation.I understand that if I remit in full, plus local tax, with this order,McGraw -Hill pays postage and handling, and a 10 -day return privilegestill applies. This order subject to acceptance by McGraw -Hill._Guidebook of Electronic Circuits (040445 -3) $24.50_Sourcebook of Electronic Circuits (040443 -7) $23.50_Electronic Circuits Manual (040444 -5) $24.75NAMEADDRESSCITY STATE ZIPThis offer good only in the U.S. and Canada. 23 -A651- 4003 -3CIRCLE NO. 22 ON READER SERVICE CARD.189

.Thebe a basic 4- function calculator, but will be sold with abooklet slanted to teach a child not only to use the calculator,but to relate to standard mathematical techniques.It may also include several "game" features. The sellingprice probably will be well under $20.00, based on presentvalues.An increasing variety of multipurpose consumer andoffice electronic products. Typically, a combination alarmclock /calendar/calculator or a combination intercom/ dictatingmachine.The development of low -cost portable electronic games.These would be based on calculator technology, but wouldbe self- contained and, unlike Magnavox's Odyssey, wouldnot require a TV set.The development of a high -output or high -intensity LED.A standard LED can be pulsed at currents many timeshigher than its average continuous rating (typically, 1 A fora 50 mA LED). If designed specifically for pulse applications,it may be possible to use a LED as a light source forspecial purpose photography (such as infrared microphotography),or even as a warning light.The development although not necessarily the commercialproduction, of solid -state energy control centers forhomes and offices. With the increasing energy crisis, overallheating /cooling efficiency becomes more and more important.There are many ways in which solid -state circuitryand devices could be used to increase the efficiency ofbuilding heating /cooling systems. Typically, controls tomonitor temperature and humidity, adjusting energy flowto maintain the proper levels without waste, controls toadjust blower speed to an optimum level for heating orcooling, and warning systems to alert the user to systeminefficiencies (such as clogged filters).That does it! Next January, we'll check our score.Readers Circuit. If you've used an ohmmeter to anyextent, you've probably been frustrated on several occasionswhen trying to interpolate a value at the "squeezed"end of the nonlinear scale found on most such instruments.A little frustration apparently was too much forreader M. J. Guenther (1169 Prairie Rd., Port Coquitlam,B.C., Canada), for he put on his thinking cap and devised alinear scale. ohmmeter, which he proceeded to build andhas been using for some time. His circuit is illustratedabove.Guenther's design features a pair of op amps, IC1 and/C2, a reference voltage source, established by R1, variousranges, selected by Si, and a voltmeter readout. Test terminalsBP1 and BP2 are provided for checking unknownresistance (Rx) values.The reference voltage obtained from R1, stabilized byvoltage follower IC1, is applied to /C2's non -invertinginput. At the same time, lC2's output is coupled back to itsinverting input through a voltage divider consisting of theunknown resistor, Rx, and a preselected range resistor, R2thru R5. The net result is that /C2's output voltage is equalto the reference voltage plus the reference voltage timesthe ratio of the unknown and range resistors. When avoltmeter is used to check the potential difference between/C2's noninverting input and its output, the initialreference voltage is cancelled, giving a reading which isdirectly proportional to the unknown resistor's value, thebasic requirement for a linear scale.Guenther used type 741C op amps in his model, butsuggests that a single type 747 dual op amp or other 741types may serve as well. The pin connections will vary, of90POWERSUPPLYRI5KR225011BPI 1SRxr4NYNAN,R3 R4 R52.5K 25K 250KLinear scale ohmmeter uses twointergrated circuits. When the circuit isproperly balanced (via range switch andpotentiometers), the meter reading isproportional to the unknown resistor.' BP2course, depending on whether a DIP, TO, or minidip typedevice is used. Range selector S1 is a single -pole, four -position rotary switch, R1 a conventional linear potentiometer,and R2, R3, R4 and R5 are small trimmer pots,although full -sized controls may be used. A dual 18 -voltregulated (orzenerstabilized) dc power supply is requiredfor operation, while the readout instrument should be ahigh- impedance VTVM or FET VM.In his letter, Guenther writes that he assembled hismodel as part of a home -built FET voltmeter, providing apushbutton switch between /C2's output and thevoltmeter's input to prevent an off -scale reading when thetest terminals are open.Except for establishing the readout voltmeter range, thereference voltage adjustment, R1, is completely noncritical,according to Guenther. He suggests calibrating theinstrument by using mid -scale value precision (1% or better)resistors as test units to adjust each range potentiometer.In his model, Guenther used test resistors (as Rx) of 50,500, 5,000, and 50,000 ohms, adjusting R2, R3, R4, and R5,respectively, to provide ranges of 0 -100, 0- 1,000, 0- 10,000and 0- 100.000 ohms.Device /Product News. If my discussion of field- effecttransistors and their applications in last November's columnstimulated your interest in these versatile devices, youmay want to investigate recent offerings by Siliconix, Inc.(2201 Laurelwood Road, Santa Clara, CA 95054): theseinclude a pair of vhf /uhf FET's and a new series ofmonolithic matched dual FET's.The new vhf /uhf devices are basically the popular U310n- channel high- frequency JFET supplied in epoxy TO -92or ceramic OD -81 package configurations. These devicesmay be used as amplifiers, oscillators or mixers.Siliconix's new dual JFET's, designated the E410 family,are epoxy -packaged n- channel devices intended for low -and medium -frequency small -signal differential amplifiersrequiring matched gate- source voltage, high common -mode rejection ratio and low output conductance. Thethree units, types E410, E411 and E412, have a maximumG -G voltage of V, a maximum G -D or G -S rating of -40V, and a maximum gate current of 50 mA, with a totalO-POPULAR ELECTRONICSpackage dissipation of 350 mW. Their common -mode rejectionratio is at least 70 dB.In addition to its new FET's, Siliconix also has announceda new line of low- capacitance, high- impedancediodes intended for circuits requiring clipping, clamping,or over -voltage protection. Identified as the PAD family(pico- ampere diode), the new devices feature minute leakagecurrents ranging from 1 pA (PAD -1) to 100 pA(PAD-100) and extremely low interelectrode capacitancesof 0.8 to 2.0 pF. The typical forward voltage drop for allunits is 0.8 volts, the maximum forward current is 50 mA,and the total device dissipation 300 mW.A new series of low- voltage varistors has been introducedby GE's Semiconductor Products Department(Bldg. 7, MD #49, Electronics Park, Syracuse, NY 13201).Performing somewhat like back -to -back zener diodes,these devices are ideal for protecting costly power transistorsagainst transient voltage peaks when used in high -current inductive circuits, such as power supplies, inverters,converters, alarms, solenoid drivers, and audio amplifiers.Physically similar to disc ceramic capacitors, thenew devices, designated the "ZA" series, are offered withratings from 26 Volts dc, 20 Volts rms to 81 Volts dc, 60Volts rms.Motorola's Semiconductor Products Division (P.O. Box20924, Phoenix, AZ 85036) has announced five new rug -gedized r -f power transistors which should be of interest tohams and other communications buffs. Designed for40 -to -110-MHz mid -band international mobile radio applications,the new devices, types MRF 230 through MRF 234,are drivers and final amplifiers rated at 1.5, 3.5, 7.5, 15 and25 watts output, respectively. Individual device gains arekept within 10 dB, while operation at VSWR's of up to 30:1,at any phase angle, can be tolerated. Unit prices rangefrom $2.30 for the MRF 230 to $16.90 for the MRF 234.Back East, RCA's Solid State Division (Box 3200, Somerville,NJ 08876) has introduced three new families ofmedium -power transistors and eight new general -purposeIC op amps.The RCA29 /SDH, RCA31 /SDH and RCA41 /SDH series aresingle -diffused hometaxial -base versions of the RCA29,RCA31, and RCA41 epitaxial base series, respectively, andare intended for a wide variety of switching and amplifierapplications, such as series and shunt regulators and driversand output stages of high -fidelity amplifiers. Allthe devices are supplied in JEDEC TO -22AB packages.The RCA29 /SDH series has typical turn -on and turn -offtimes of 2.3 us and 6 us, respectively, with a minimum betaof 15, measured at 1 ampere. VCEO ratings range from 40 to100 volts, depending on type. Featuring similar turn -onand turn -off times, but a minimum beta of 10, measured at3 amperes, the RCA31 /SDH series is offered with comparableV,.EO ratings. Finally, the RCA41 /SDH series has typicalturn -on and turn -off times of 3.2 ps and 3.7 us, a minimumbeta of 15 at 3 amperes, and voltage ratings of 40, 60, and80 volts, depending on type.Designated types CA107T, CA207T, CA307T, CA101T,CA101AT, CA201T, CA201AT and CA301AT, RCA's new ICop amps are direct replacements for standard industrytypes such as the 107, 207, 307, 101, 101A, 201, 201A and301A in packages with similar terminal arrangements.These are dual -supply, high- input- impedance devicessuitable for use in sample and hold, comparator, low -frequency waveform generator, long- interval timer, summingamplifier, and multivibrator applications. All eighttypes are furnished in 8 -lead TO -5 style cases. pJANUARY 1975CI-L -ELEROCSNew`MIL..linedMM MI,"` dJ :1975 7pa Engineering 11,2`':;: = Manual &In '- ;;u.VIIV-tiLI!J5( uua`mv.s. u `so Guide!PurchasingINHforA "must"hobbyists, experimenters,repairmen and technicians,Thousands of hard -to-get electronicparts -and supplies.NAMEOrder nowto Allied ElectronicsEast 8th St.Send $1Dept. PE75, 401Fort Worth, Texas 76102ElHO'`'l./.jíMIlaMO aADDRESSami CITYSTATE ZIP11laLUEDHIXI o [I:NameELECTRON /CSLA A DIVISION OF TANDY CORPORATIONC3111 r MIDE-7"Send for FREE Tiger booklet (20pages) which answers all yourquestions.AddressCityStateZipCLIP OUT THIS AD AND SEND TO-TRI -STAR CORP.P. 0. Box 1727 Dept. EGrand Junction, Colo. 81501CIRCLE NO. 35 ON READER SERVICE CARD91

'CB'S RED BARONTHERE we were at 1,000 feet,our wings at a crazy angle, theground rushing up, when all of asudden ....That's how it felt when I recentlytook a ride with one of the world'srarest birds -a flying CB reporter. Hisname is Morgan Kaolian, and he pilotsa flivver of a plane on weekends for alocal radio station located near the bigboating areas of New York and Connecticut.Morgan's become somethingof a legend in these parts because hebuzzes through the air for 18 hoursevery weekend to deliver half -hourlybroadcasts of weather, fishing, seaconditions and road traffic, plus a fewsurprises. When I caught wind thatMorgan depends heavily on CB, I decidedto investigate, and maybewangle a free hop in his flyingmachine.Most people think flying reportersare in helicopters. Not so in this case.The plane is aviation's Model A; atwo -place Cessna -150 that cruisesabout 90 mph, squeezes 15 milesfrom a gallon of gas and emits aboutas many decibels as an overweightwasp. A helicopter, on the other hand,noisily chomps the air, costs upwardsof $80 an hour to operate and is usuallyan expensive big -city bird.Morgan's mini -machine slashes thecost, and CB takes a share of thecredit in the electronic department.When I first spoke to Morgan on thephone he asked me how much Iweighed. "One hundred ninety," I replied,wondering if the beefy figurewould ground me. The reason heasked is that the plane is loaded tothe gunnels with radio equipment andsprouts antennas like a flying porcupine.A two -way vhf link on 161.7MHz carries his voice to the groundfor retransmission over WICC, an AMstation on 600 kHz. In the instrumentpanel there's an AM receiver so hecan monitor the radio announcer forcues (but a closer look reveals it to be92CB SceneBy Len Buckwalter, K1ODHa Volkswagen car radio!). Back in theminuscule baggage compartment is atypewriter -size vhf radio and the restof the cabin is criss- crossed with themicrophone cords and danglingheadphones. With all this electronicsaboard, no wonder Morgan was concernedabout poundage.The CB installation turned out to besomething less than you'd findaboard a Boeing and more like a typicalhobbyist's shack -a disarraythat's understood only by the personwho grew it. Since the Cessna's Lilliputiancabin was already burstingwith instruments, the CB set wasstuffed into a map pocket behindthe backrest of a seat. The tinyknobs of the CB rig peeked out ofthe pouch like a baby kangaroo. Theantenna installation, though, was anaircraft -type spike loaded for CBchannel 13 and permanently mountedon the fuselage. Power for the rig waspicked up through the aircraft's12 -volt dc buss in automobile fashion.As we taxied out for take -off, thepilot clamped on headphones andhanded me a pair. The "cans" were acomfortable set -until Morgan turnedup the audio with a wicked smile. Allthe plane's radios feed into thephones simultaneously. Trying tocatch the voices of the control tower,ground controller, CB receiver, vhfreceiver and AM monitor would beFlying reporterMorgan Kaolian usesCB for much of hisaerial communications.easy if I were a 5- channel tape recorder,but Morgan has been doing it for8 years and easily sorts out the audiobedlam. As the 100 horses of theCessna engine struggled to lift us intothe air, I regretted the box of Oreos Ihad eaten the night before."Hey, here comes Eddie Rickenbacker!"It was the first CB voice ofthe flight. Morgan wheeled the planearound and headed toward a row ofboats moored below, then loweredthe plane's right wingtip to point out asingle cabin cruiser. "That's the citypolice," he explained. "They monitorchannel 13." Morgan exchangedpleasantries with the floating policeand I was suddenly impressed at thegood fortune of CB- equipped boatmenin the area. Maybe the U.S. CoastGuard won't hear CB distress calls,but there's a good chance they'll beintercepted by this channel 13search -and -rescue team.On an average weekend Morgansaves about two boats in distress. It'smost efficient if the boat has a CB rigbecause its captain simply calls onchannel 13 and may speak directly tothe aerial angel -of -mercy himself. Therange of a CB "air mobile" is verygreat with its lofty antenna, and talkingdistances of 50 miles are average(or double that when altitudes rise tothree or four thousand feet). If a boathas no CB, Morgan may flit to anearby boat and direct it to the crippledcraft. When radio communicationswon't work he relies on moresensational feats. He'll drop writteninstructions in a sandwich bag or flydown low and shout directions."Won't the noise drown out yourvoice ?" I asked, with some doubt."No, I kill the engine gliding down."Morgan's uncanny skill at skimmingthe waves reaps anotherbonanza for CB'ers in the area. It'sfish -spotting by air. To demonstrate,he lowered the Cessna's nose andasked me, "Do you have any aversionto low flying ?" As the sea rapidlyfilled the windshield, I replied, "Nn-n-no."Blue fish, he explained, arevisible as they break the surface,while bunkers expose themselves bythrashing about. Schools of fishbelow the surface look like darkholes. If he spots any giveaway signs,he'll report them to CB'ers below whocall in. He's even been known to assistunlucky anglers with a helpful"Follow me."The plane was now over land andflying parallel to a busy interstatethruway. Although he gives traffic reportson his regular AM broadcasts, Iwanted to see the interaction betweena CB- equipped piane and anautomobile in motion. We raised amobile who described himself as ayellow Chevy pickup truck with a loadCB set is carried inpocket behind seat.of lumber travelling on Route 1. Secondslater, over a tangle of roadschoked with homeward -bound vehicles,Morgan started circling. "Do yousee it ? ", he asked me. All I could seewas traffic -but it seemed he spottedeverything below about an hour beforeI did."I see you!" peek -a-booed the yellowChevy. Finally, looking like aTonka Toy, the teeny mobile with itsmatchstick load of lumber caught myeye. Morgan nudged me and, with agleam in his eagle eye, said; "I estimatehe's going 30 miles per hour."He squeezed the CB mike and firedthe question."I'm going 30 miles per hour" answeredthe yellow pickup.Morgan's ability to interface withroad traffic has even rescued lostsouls on the ground. One time on CBhe heard; "Does anyone know whereJANUARY 1975Antenna, on plane's fuselage,is cut for channel 13.the church is on Brooklawn Road?Some fellow is on his way to a weddingand he's lost.""Where are you ?" asked Morgan.When the driver gave his location,Morgan swooped down like a hawkon a hapless hare."Is that you in the red Corvette ?""That's me.""Well just keep going, the church isstraight ahead." Chalk up anothersave for CB. Morgan even saw theman going to the wedding!The airport runway lights were alreadyglowing as our Cessna toucheddown at the end of the day. Momentsbefore we had listened on channel 10,with its CB- equipped truckers talkingof roads and loads, or inviting eachother to coffee at the next stop. I wassurprised by one trucker who askedanother driver if he had a "reefer."Morgan quickly explained that hemeant a "refrigerated" truck. (Heseems to know a little about everything,which may explain why he'salso called the "Flying Mouth. ") Atwist of the selector to CB channel 9brought remarkable silence, consideringthat it's often misused and ourreceiving range in the air was sogreat.Morgan and his aerial antics via CBmay serve as an inspiration for otherpilots and communities. He's spreadingtremendous goodwill for CB andproving the medium's worth in publicservice. The only precaution is thatthis sort of activity should be doneonly by experienced airmen. Morganhas a good luck charm (an "evil eye ")pinned to the roof of his cabin, but his8 years of accident -free reporting isalso helped by 4,000 hours in the airand his experience as a military flier.Thanks to him we can say CB is onland, at sea -and in the air, too!STEREO COMPONENTSLargest selection of top namebrands...try us and see.....\ nJÌ°jpy I md IIIIllllll6330 Frankford Ave.Baltimore, Md 21206All mail answered within 24 hoursPhone Daily 9 AM to 9 PMSaturday 9 AM to 4 PMPhone (301) 488 -9600I r,CIRCLE NO. 37 ON READER SERVICE CARDOlsonCatalogVALUE PACKED WITHTHOUSANDS OFELECTRONIC BARGAINSWe Will Send You TheNext 7 Issues FREE!You'll Find The BestOf the Name BrandsPlus ExclusiveOlson Products atLow, Low Prices!FREESendTodayOlson Electronics Dept. 13260 S. Forge St., Akron, Ohio 44327NameStreetCityStateApt. No.ZipCIRCLE NO. 26 ON READER SERVICE CARD93

iRECEPTION AND THE ATMOSPHEREHAVEyou ever turned yourreceiver on and tuned across aband only to find that it was completelydead? This has probably happenedto every amateur at one time oranother. The first reaction is, "Oh, no!Something's gone wrong with my receiver!"In most cases, though, thefault lies not in the gear but in thepropagation conditions affecting theband or bands. Why are bands sofickle and unpredictable?The reasons for such occurrenceslay in the interaction of the atmosphere,the sun, and radio waves. Let'sconsider the nature of these relationships,and how they affect radio communications.Our atmosphere consists of fourdistinct regions -the troposphere, thestratosphere, the ionosphere, and theexosphere. Two of these strata directlycontribute to the propagation ofradio waves. The troposphere, whichextends from 0 to 7 miles, (0 to 11.2km) can act as a waveguide for vhf anduhf signals, but has little effect on hftransmissions, as does the stratosphere,which extends from 7 to 25miles (11.2 to 40 km). From 25 to approximately250 miles (40 to 400 km)we find the ionosphere. In this region,rarified gas molecules and atoms canlose some of their electrons when excitedby solar radiation. They disassociateinto ions and free electrons,having positive and negative charges,respectively. Since the ions arethousands of times more massive thanthe electrons, they tend to be muchless mobile. The electrons, however,tend to cluster in layers -the D layer,at 37 -57 miles (60 -92 km). the E layer,at 62 -71 miles (110-115 km), the F1layer, at 99 miles (160 km), and the F2layer, found between 130 and 261miles (210 -420 km), depending on theseason, the degree of ionization, andother variables. (See diagram shownat right.)At night, the picture changesslightly. In the absence of the ionizing94AmateurRadioBy Herbert S. Brier, W9EGOsolar energy, the D layer disappearsafter sunset. The E layer, which likethe D reaches its maximum ionizationlevel at noon, is at a minimum aroundmidnight, when the free electrons recombinewith the ions in the absenceof solar radiation. The F1 and F2 layersmerge into a single F layer after sunset,at a distance between those of thendividual layers. Sincethedistributionof atoms at this height is so thin, therecombination process is muchslower than in the D or E layers. Maximumionization occurs at noon, andtapers off very gradually after that, remainingat a fairly high level throughthe night. A minimum is reached justbefore sunrise, at which point theionization increases rapidly. Within anhour or two, it is back to daytimelevels.The final stratum, called the exosphere,is made up mostly of protons(hydrogen nuclei), and other chargedparticles that have been carried fromthe sun as part of the "solar wind."This region acts as a primary shieldagainst the buffets of solar disturbances,but its effect on radio propagationis not great.When the transmitter, at T, causesthe antenna to radiate, the waves willleave the antenna at various angles.The one that travels straight up entersthrough the ionization layers and escapesinto space, never to return.WAVE ESCAPESINTO SPACEOther waves leave the antenna at variousangles from the tangent. Let uslook at two of the signals. The wavewith the higher departure angle, alsocalled the wave angle or angle ofradiation, first enters the D layer,where it is attenuated to a degree inverselyproportional to its frequency.This is due to the fact that each timethe signal collides with an electron orion, part of its energy is lost in excitingthe particle. Since the D layer is sodense, much attenuation takes placehere. D -layer absorption is so great atlow frequencies (5 MHz and below)that most of the signal doesn't make itthrough this layer. This is why 160and 80 meters are usually "dead" duringthe daytime, but can open up atnight.If the signal is strong enough,and /or of high enough frequency, itwill pass through the D layer with agood degree of strength. It will thentravel up to the E layer. If the E ionizationis high enough, and the waveangle is below a critical value, it willbe reflected back toward the earth atabout the same angle as the incidentone. The wave will then pass throughthe D layer and reach the earth at agood distance from the transmitter.If the E layer is not highly ionized,the wave will pass through it andreach one of the F layers, although itsdirection may be modified by partialbending. When the wave reaches theF layer, it will be reflected back towardearth if the wave angle is lessthan the critical value, and the frequencyis below the "maximum usablefrequency," or MUF. If the angleand /or frequency is greater thanthese values, the wave will pass intospace. If the wave is sent back, it willpass through the other layers, andperhaps be sent back up by the Elayer, and reflected down by the Flayer at another point. The greatestrange available from a "single hop"Signals may be reflected by a layer of the ionosphere or escapeinto space. Range is determined by layer height and wave angle.POPULAR ELECTRONICSFREE INFORMATION:Learning more about aproduct that's advertisedor mentioned in an articlein this month's issue is assimple as one, two, three.And absolutely free.Print or type yourname and addresson the attached,postage -paid card.Use only one cardper person.Circle the number(s)on the cardthat correspondto the numbers]at the bottom ofthe advertisementor articlefor which youwant more information.(Key numbers foradvertised productsalso appearin the Advertisers'Index.]Simply mail the01613. postage -paidcard.6-Use only one card per personPOPULAR ELECTRONICSUse only one card per person.NAMEADDRESSCITY11631466176STATEPE1753[Zip Code must be included to insure delivery) [Void after Mar. 31. 1 975)Do you build or assemble electronic equipment?A) Yes B) No If yes, please check below.C) From complete kits D) From separate parts2 317 1832 3347 4862 6377 7841934496479520355065806 721 2236 3751 5266 6781 828 9 10 11 12 13 1423 24 25 26 27 28 2938 39 40 41 42 43 4453 54 55 56 57 58 5968 69 70 71 72 73 7483 84 85 86 87 88 89POPULAR ELECTRONICSUse only one card per person.NAMEADDRESSCITYSTATE153045607590PE1752(Zip Code must be included to insure delivery] [Void after Mar. 31. 1975)Do you build or assemble electronic equipment?Al Yes B) No If yes, please check below.Cl From complete kits D) From separate parts1 216 1731 3246 4761 6276 773 418 1933 3448 4963 6478 795203550658062136516681722375267828233853688392439546984102540557085POPULAR .LECTRONICSUse only one card per person.NAMEADDRESSCITY11631466176STATE11264156718612 1327 2842 4357 5872 7387 88142944597489153045607590PE1751(Zip Code must be included to insure delivery.) [Void after Mar. 31, 1975)Do you build or assemble electronic equipment?A) Yes B) No If yes, please check below.C) From complete kits D) From separate parts2173247627731833486378419344964795203550658062136516681722375267828233853688392439546984102540557085112641567186122742577287132843587388142944597489153045607590

OM:FREEINFORMATIONFirst ClassPermit No. 217Clinton, IowaBUSINESS REPLY MAILNo postage necessary if mailed in the United StatesPOSTAGE WILL BE PAID BYPopular Electron ¡esRO. Box 2905Clinton, Iowa 52732First ClassPermit No. 217Clinton, IowaBUSINESS REPLY MAILNo postage necessary if mailed in the United StatesPOSTAGE WILL BE PAID BYPOM1 lar E led ron icsRO. Box 2905Clinton, Iowa 52732First ClassPermit No. 217Clinton, IowaLBUSINESS REPLY MAILpostage necessary if mailatl'in mailed in the United nitetl States tatasPOSTAGE WILL BE PAID BYPopular ElectronicsRO. Box 2905Clinton, Iowa 527327ËXH1975EXPERIMENTER'SHANDBOOK -Winter EditionIt's by the editors of POPULAR ELEC-TRONICS -with features and articles and completelab- tested instructions that guarantee successfulhours and months of mind -absorbing projects for fun andpracticality. This latest 1975 Winter Edition helps you get ittogether . . with a score of build -it- yourself projects. Nowyou can confirm extra -sensory -perception with "THE ESPCOMPUTER TESTER "! It's the sophisticated random -numberelectronics project with digital readout ... allows you to determinelaws of probability . introduces you to digital electronicsBUILD A COSMOS DIE -it can teach you how to usecomplementary -metal-oxide semiconductors, the hottest devicetoday THE ALPHA BRAIN WAVE FEEDBACK MONITORcan help you produce the brain -wave frequency band to clearyour mind of distracting thoughts and achieve calmnessquickly You can streamline your home lab with the DIRECTREADING CAPACITANCE METER -it will check values ofcapacitors directly on a meter scale Or build the PRECISIONLAB POWER SUPPLY, a regulated supply that delivers up to 30volts and 1.2 amps Or build a PREAMPLIFIER FOR YOURSCOPE. Other projects include the DIFFERENTIAL- TEMPERA-TURE BASEMENT VENTILATOR MONODIGICHRON, a one -digit electronic clock that displays hours and minutes insequential form ELECTRONIC WIND CHIMES AUTOMATICAMPLIFIER SWITCH AN ANTENNA TUNER FOR SWLersA KEYLESS VEHICLE BURGLAR ALARM RECHARGEABLEFLASHLIGHT 3- CHANNEL COLOR ORGAN, and much more.All with complete construction plans, including parts lists andprinted- circuit board patterns. Many products are unique designs,not available anywhere else.ONLY $1.25CB- HAM- SWL...they come throughloud and clear in theall -new 1975COMMUNICATIONSHANDBOOKMYrAiI®NSMñ1®®061I 1875=want Ml AMC plpR TOWWhether you're an old hand or justgetting started, this vital "how -to" guide willhelp you get greater value, greater enjoyment out ofevery minute you spend with your equipment. CITIZENS' BAND-What it is, how it is used, how to get a license, how to setup your station, Business Radio Service, Single -Sideband CB,PLUS 3 handy buyers' catalogs. AMATEUR RADIO -How toapply for a novice licence, how to train and qualify, how toset up your rig, latest trends including 2 -meter FM and slow -scan TV, PLUS -illustrated Ham Equipment Directory. SHORT-WAVE LISTENING -How to choose and use SWL equipment,all the shortwave bands around the world plus a list of leadingDX clubs and a complete BUYER'S GUIDE with full specs onall known general coverage SW receivers. SPECIAL BONUS -Includes "Shortwave DX'ing ", "Public Weather Broadcast Frequencies,"Changes in Marine Communications, and a Directoryof all monitor receivers for picking up police, fire andpublic service broadcasts.ONLY $1.25HERE'S HOW TO ORDERMail your order along with your name, address and remittancein the amount of $1.25 plus 35c for postage andhandling for each copy ordered. Please be sure you specifythe exact title of the publication ordered -1975 ElectronicExperimenter's Handbook -Winter Edition; 1975 CommunicationsHandbook.MAIL ALL ORDERS TO- ZIFF -DAVIS SERVICE DIVISION,DEPT. W, 595 BROADWAY,NEW YORK, N.Y. 10012.PLEASE ENCLOSE PAYMENT WITH ORDERRick, WB9EWQ, uses a HeathkitElectronic Keyer with HW -16and HW -101 transceivers.off the F layer is about 2500 miles(4000 km), and about 1250 miles(2000 km) from E -layer reflection.The range available from this ionosphericreflection (also called sky -wave propagation) depends on theheight of the layer(s), the degree ofionization, the angle of radiation andtransmitter output power. In the diagramare two sky waves received at R1and R2. The angle of radiation of thewave reaching R1is much greaterthan that appearing at R2, and therange, as you can see, is much less.While it is possible to cover the distanceto R2 by more than one hopwith a higher angle of radiation, themulti -hop signal will be weaker. Eachtime the wave hops, it loses about 6dB or one "S" unit of strength. Atwo -hop signal would thus be 12 dBweaker than one which arrives after asingle jump.Amateurs who wish to work DX areinterested in having antennas whichradiate the larger portion of appliedpower at low angles. It has beenfound that the median wave anglesfor distant signals arriving at the receiverantenna on the hf bandsare -28 MHz, 9 degrees; 21 MHz,12 -14 degrees; 14 MHz, 15 degrees; 7MHz, 30 degrees; and 3.5 MHz, under45 degrees. For horizontal dipoles,the following heights will give the desiredradiation patterns: 28, 21 and 14MHz -70 feet; 7 MHz -70 to 90 feet;and 3.5 MHz -90 to 140 feet. Theseheights are not absolute, since thereare times when a lower or higherheight would be more desirable.Solar Influences. The degree ofionization is dependent on the activitiesof the sun, and the proximityof the earth to the sun. Sunspots aredirectly related to the levels of solarradiation. When there are many sun -JANUARY 1975spots, the ionization level go up.There is an eleven year sunspot cycle.The last maximum occurred about 5years ago, and we are now well intothe waning period.As we are well into the waning yearof the current sunspot cycle, the 14 -,21 -, and 28 -MHz bands will normallybe dead after dark for the next fewmonths -except for unpredictable"short- skip" propagation conditionsthat can occur at any time on thesebands. In addition, unless you havebetter -than -average 3.5- and 7 -MHzantennas, signals on these frequenciesbecome weak and hard to workas the evening progresses. If your antennasystem is less than top- notch,you may hear operators with good3.5- and 7 -MHz antennas having notrouble working stations you canbarely copy. Unless you can put upbetter low- frequency antennas, theeasiest way to cope with the situationis to do more daytime operating. Althoughthe 28 -MHz band will often bedead, even in the daytime, the 3.5-to -21 -MHz bands are and should continueto be useful for distances from100 to several thousand miles frommorning to night for the next fewyears.You will also feel the effects of seasonalinfluences. Since the earth iscloser to the sun in winter, F2 ionizationis more intense and higher MUF'sare the rule. E -layer MUF's are generallylower in winter than in summer.The F1 layer often disappears entirelyduring the winter, while it demonstratesMUF's of about 5 MHz in thesummer. Night -time MUF's during thewinter of the minima may drop to lessthan 4 MHz, as you will notice overthe next few months.If hf conditions deteriorate to thepoint where few contacts are possible,and you are looking for more050's, investigate the amateur vhfscene. If your attention has beenfocussed on the frequencies below 30MHz, you cannot imagine the populationexplosion that has taken place onthe amateur frequencies above 50MHz -especially on the 144 -148 -MHzband. This is due to the wide availabilityof low -power vhf FM transceiversabout the size of a big box ofcandy. When these units are used inconjunction with the vhf repeatersthat have sprung up all over the country,ultra -reliable local communicationshave become an actuality forany operator within 25 or 30 miles of arepeater. Antennas need not beelaborate.For further information on modernvhf operation, try the VHF HandbookFor Radio Amateurs, by Herbert S.Brier, W9EGQ, and William I. Orr,W6SAI, Radio Publications, Inc., Wilton,Conn., or FM and Repeaters,ARRL, Newington, Conn. Thesebooks are available from mostamateur equipment distributors.In addition, do not hesitate to putout a couple of CQ's on an apparentlydead band. One of the never -endingfascinations of amateur radio is itsunpredictability. Also, the bands areoften open to remote localities; andno one ever finds out because of thelack of activity at the right times andplaces. Evidence of this is furnishedin practically every amateur contest.News and Views. Send news,comments and pictures for possiblepublication in this column to: AmateurRadio, Herbert S. Brier, c/aPOPULAR ELECTRONICS, One Park Ave.,New York, NY 10016. .SELECTED CONTESTSARRL VHF SS Contest; 2:00 P.M. localtime, Saturday, Jan 7, to midnight, localtime, Sunday, Jan. 8, 1975. Exchange:number of contest contact; "A" if yourpower input is less than 50 watts, "B" ifit is 50 watts or more; your call letter;"check" last two digits of year licensed;ARRL section.International DX Contest (ARRL);0001 GMT, Feb. 4 to 2359 GMT, Feb. 5,and same time March 4 and 5; phone.Same times, Feb. 17 and 18, and March17 and 18; CW. Send signal report andname of your state or province to eachDX station worked. Receive signal reportand power input. Score: add thenumber of different stations worked oneach band and multiply by number ofdifferent countries worked.Novice Roundup (ARRL); 0001 GMT,Feb. 4, to 2359 GMT, Feb. 12; operate atotal of 30 hours. Novices can workanybody. Others work only novices. Exchangecall letters, signal reports, andname of ARRL section. Novice scoring:add the number of different stationsworked to the highest code speed recordedon your ARRL code -proficiencycertificate. Multiply by the sum of sectionsand countries (other than ARRLsections) worked.Complete literature and last- minuterule changes for each of these contestsare available from ARRL, Newington, CT06111, upon request accompanied byan addressed return envelope. Affix 8cents postage for 3rd class return, 30cents for first class. Send scores tosame address.97

11REJUVENATING ELDERLY EQUIPMENTALTHOUGH most of us wouldlike to purchase the best testgear that we can afford, we often haveto compromise when it comes to cost.This means that many workbenchesmay have test gear whose specificationsare not much better than theequipment being tested. In whichcase, we may be violating one of thebasic rules of good engineering (andservicing): test gear must be at leastone order of magnitude more accuratethan the device being tested.In many instances, a few more yearscan be squeezed out of the old gearsimply by "swiping" partial or wholecircuits out of magazines like POPULARELECTRONICS. Although most of usnever build even a small percentage ofthe various circuits we see, we shouldtake a close look at them with an eyefor ideas to improve our present testequipment. Over the past few years,we have found many circuits thatcould be used to upgrade our testgear. The best part of this approach isthe very low cost involved. (The fewhours of bench time required to assemblethe circuits are actually enjoyablewhen you're accomplishingsomething.)Consider an elderly square -wavegenerator. This old timer might dovery well at the lower audio frequencies;but as the frequency goes up, theoutput square wave probably resemblesa badly warped triangle wave, atbest. You can try to improve the high -frequency response by using the outputto drive some digital logic, such asa flip -flop. This would work, but youwill need a 5 -volt power supply, andthe frequency will be halved. ASchmitt trigger circuit would probablywork fine. However, you might want totry the circuit shown at (A). It convertsthe battered old waveform into an impressivesquare wave with fast riseand fall times, reaching way out in frequency.The amplitude is also constantover the entire span. We built this98Test EquipmentSceneBy Leslie Solomoncircuit right into the old generator, takingthe required power from the internalsupply. Any silicon switchingtransistors and diodes can be used.The input potentiometer (Rl) is adjustedfor the best output waveform.Once set, this control requires nofurther calibration. Potentiometer R2is used to set the output amplitude.Diode D1 protects the Q2 emitter -basejunction while diodes D2 and D3 preventthe clamp voltage from reversebiasing. Q1. The input is driven fromthe maximum output of the oldsquare -wave generator.Another piece of gear that neededhelp was an old oscilloscope. Althoughit had the usual 1- megohm impedance,we found that it did loadsome of the newer circuits, especiallywhere CMOS or bootstrapping wereCircuit (A) can beused to improvethe waveform on asquare -wave generator;while (B) can be addedto an oscilloscope toreduce input impedance.+20VMAX-6VINRI10Kused. To reduce this loading effect, webegan using a 10:1 divider to increasethe input impedance. But this, naturally,reduced the signal level availableto the scope. We then had to crank thevertical gain way up, and sync sometimesbecame unstable.The circuitshown at (B) uses a form of bootstrappingto produce an input impedancesomewhere around 1000 megohms.The circuit has unity gain, while theupper frequency equalization is determinedby the setting of the5000 -ohm potentiometer.The rise time is quite fast, and isestimated at about half a microsecond.The circuit was built on a narrowpc board and mounted within anold metal cigar tube container, as aprobe. We have had no circuit loadingproblems.Although we have shown only acouple of relatively simple ideas, thereare many more. Where do these ideascome from? When we receive ourquota of construction and hammagazines, besides reading those articlesthat interest us, we take a look atall the circuits, searching for ideasthat may sometime be useful. Once wesee something that could be of use, weclip it out and file it in a set of foldersthat are categorized by applications -audio, test gear, power supplies, etc. Ifyou don't like the idea of cutting up2.2 K01HEP50DI-03=1N914( A)DI(B)10KOUTPUTR25KIKPOPULAR ELECTRONICSmagazines, then start a card file, recordingthe title of the article, themagazine, the month and year, thepage number, and the idea you have inmind. At some later date when you arelooking for help, all you do is look inyour files under the proper heading,find the article, break out the solderingiron, and update.Circuit Loading. Several times in thepast, we have mentioned that measuringvoltage with a VOM is not the sameas measuring it with a VTVM, VTM,DMM or any other high- inputresistanceinstrument.Let us take the case of a circuit havinga 10 -volt power supply and a seriesoutput resistance of 50,000 ohms. Ifyou are using a VOM with a20,000 -ohm dc resistance, the currentflow through the circuit will be 10/ (7 x10'), with the 70,000 ohms being thesum of the 50,000 -ohm series resistanceand the 20,000 -ohm VOM resistance.The current is then 1.43 x 10 'amperes. The voltage drop availableto the VOM (1.43 x 10 ') (2 x 10') or2.86 volts. The error is then (10- 2.86)/10 times 100 or 71.4 %.If you plug the VTVM 10- megohminput resistance into the above equationsin place of the 20,000 ohms of theVOM, you will find that the currentnow becomes 9.95 x 10 amperes.The voltage drop across the VTVM isnow 9.95 volts, and the error is only0.5 %.You can use the dc resistance ofyour own VOM and VTVM (or otherhigh input resistance voltage instrument)to determine for yourself justhow inaccurate those voltage measurementshave been in the past. Youwill see that the higher the input resistanceof the voltage measuring device,the greater the accuracy. 0:Ill...

1°spend adime,save a mint.Invest a dime and send for our catalog.We'll prove to you that you canhave selection and convenience andstill get a great price.For an immediateFREE copy of our64 -page catalog, includingpull -out"Hifi Primer " sec -tion, mail the couponbelow to the locationnearest you.Please print.lis li i---MidwestWholesale& MAIL ORDER DIVISION1626 Ogden Ave. (US 34), Downers Grove, III. 605153309 E. Carpenter Frwy. (Texas 183(, Irving, Tex. 75062rNAMEADDRESSLITY /STATECIRCLE NO. 25 ON READER SERVICE CARDLARGE -LARGEli]illliZIPLOW - LOWPRICESNATIONALLYADVERTISED STEREO EQUIPMENTAT LOWEST PRICES!TURNTABLES SPEAKERS RECEIVERSAMPLIFIERS - TAPE RECORDERSWRITE FOR QUOTE ONNATIONALLY ADVERTISED BRANDS OF STEREOCOMPONENTS. SATISFACTIONGUARANTEED!HI -FI WHOLESALERSP. 0. Box 809Kankakee, Illinois 60901(815)- 939 -7868CIRCLE NO. 10 ON READER SERVICE CARD100Electronics LibraryTHE COMPLETE SHORTWAVE LISTENER'SHANDBOOKby Hank BennettHere is a thorough, "hands -on" discussionof all the facets of shortwave radio listening.The author, using his own SWL experience,and that of others, answers questionssuch as "What SWL's hear," "Whythey listen," and "How to get started,"among others. The purpose of the book isto expose newcomers to the hobby, and toprovide the experienced listener with valuableinformation to hunt down new stations.The reader is introduced to the terminologyand the hardware of the hobby, as wellas propagation phenomena. Tips are givenon the selection of a receiver, installationof an antenna, and times and frequenciesfor the reception of various parts of theworld. The more exotic "sports" of FM andTV DX'ing are given special attention.Chapters are also devoted to amateur andCB radio, logbooks, reports, card swapping,and radio clubs.Perhaps the most valuable aid in thebook is a thorough list of foreign stations,by country, which includes exact frequenciesand times of transmission. There isalso included a discussion of the DX possibilitiesfor the various frequency bandsgiven the time of day, the season, and thepoint in the 11 -year sunspot cycle. If youare entertaining notions of involving yourselfin shortwave listening, there are fewsources which can whet your appetite aswell as this.Published by Tab Books, Blue Ridge Summit,Pa. 17214. 281 pages. $.9.95 hardcover;$6.95 paperback.TRANSISTOR FUNDAMENTALSAND SERVICINGby B. LarsonThe text covers the fundamentals of electronicdevices to instruct readers in servicingcircuits and systems in which they arefound. Among the topics discussed arediodes, power supplies, bipolar transistors,bias circuits, ac amplifiers, FET's,IC's, oscillators, vacuum tubes, and the oscilloscope.Troubleshooting methods foreach of these components and networksare given. Packaging and conventions forthe various active elements are given. Theemphasis in this book is on servicing,rather than design, with circuits reduced tothe bare essentials and presented in ahighly simplified manner. Short- answer,multiple- choice questions and problemsconclude each chapter.Published by Prentice -Hall, Inc., EnglewoodCliffs, NJ 07632. 462 pages.$14.95, hard cover.DIGITAL COMPUTERS:CIRCUITS AND CONCEPTSby Deem, Muchow, and ZeppaThis is a sophisticated text for the technician,engineering student, or practicingengineer who wants to know how digitalsystems operate, and how such systemscan be designed at minimum cost andparts count. Among the topics covered arenumber systems, Boolean algebra, logicsymbology, code and data representation,Karnaugh maps, and simplification of logicalexpressions. Circuitry is not neglected.A thorough description of the RTL, DTL,TTL, ECL and CMOS logic families is included.Shift registers, combinational andsequential circuits, decoders and encoders,timing and control operations areanalyzed and implemented to realizemathematical operations in the serial andparallel modes. Memories are given specialconsideration.Published by Reston Publishing Company,Box 537, Reston, Va. 22090. 376 pages.$14.95, clothbound.MODERN RECORDING TECHNIQUESby R. E. RunsteinThis new work introduces the reader to theequipment and practices found in today'smultitrack recording studios. In the firstchapter, the acoustical, mechanical, electricaland magnetic means of transforminga live performance into a disc are outlined.Later chapters describe consoles, microphones,mixing, noise -reduction andmonitoring. Finally, automated mixdown,disc cutting and pressing, and quadraphonicdisc systems are presented.Published by Howard W. Sams & Co., 4300W 62nd Street, lndianpolis, Ind. 46206. 368pages. $9.95, paperback.BASIC ELECTRICITY: A TEXT -LAB MANUAL(Fourth Edition)by P. ZbarDesigned as a programmed text for an introductoryelectricity laboratory course,this volume presents basics of theory aswell as practical applications of electricity.The reader is introduced to the passive circuitelements and their properties. Ohm'sLaw, series and parallel circuits, and voltagedividers are explained with actual circuitsthe reader can assemble. Kirchoff'sLaws, Thevenin's and Norton's Theorems,and maximum power transfer are explored.Time constants, reactive circuits, impedance,and ac analysis conclude thecourse. If the book is used as a lab manual,POPULAR ELECTRONICSstudents who follow it should gain a basicworking knowledge of electrical networks.Published by McGraw -Hill Book Co., 1221Avenue of the Americas, New York, NY10020. $6.95, soft cover.VHF HANDBOOK FOR RADIO AMATEURSby Herb Brier and William OrrThis guide to the "line -of- sight" frequenciesbegins with a short history of vhf explorationand experimentation. The mostpopular vhf bands include more than 13MHz of spectrum space, more than fourtimes the capacity of the hf bands. Sincemany amateurs are moving higher andhigher to avoid congestion and QRM, thisbook will be a valuable reference work fornewcomers to the high bands. Vhf propagation,caused by ionospheric reflection,moonbounce, tropospheric, auroral, andmeteor effects is explained. The Oscarseries of satellites is examined, and specialemphasis is given to earth -station configurations.The very popular FM scene, includingrepeaters, mobile links, and tone -encoding controls is discussed. Designtheory and construction practices for antennas,solid -state amplifiers and receivingcircuits are explained and illustrated.Published by Radio Publications, Box 149,Wilton, CT 06897. 336 pages. $5.95, softcover.ELECTRONIC TEST EQUIPMENT-AND HOW TO USE ITby J. RisseA guide to the practical uses and properoperation of test equipment, this bookgives principles, functions, and applicationsfor tube and semiconductor testers,signal generators, capacitance and inductancebridges, and oscilloscopes. A list ofkey questions is included at the end of eachchapter to allow the reader to check himselfon new material as it is presented.Published by Tab Books, Blue Ridge Summit,PA 17214. 204 pages. $7.95, hardcover; $4.95, paperback.SOLID STATE IGNITION SYSTEMSby R. Graf and G. WhalenFundamentals of the various electronic ignitionsystems that are becoming more andmore popular in today's cars are discussed,and the conventional Ketteringsystem is examined. Inductive -dischargeand capacitive- discharge using solid -statecomponents are covered by describingrepresentative types offered by auto manufacturersand supply houses. Triggermethods, from breaker -point (with COI) tomagnetic "pointless" systems available asan option on most new American cars areincluded.Published by Howard W. Sams & Co., 4300W 62nd Street, Indianapolis, IN 46206. 136pages. $4.50.JANUARY 1975Plug ¡n...wireAmpziflais here...Why spend $750 to $1200 dollars foran amplifier? The GreatRI American Sound Companysells one with a full comple-I mentary series connected out-. put for much less. In shortE,AMPZILLA is here. In theSeptember 1974 Popular Elec-Ironics, Hirsch -Houck Labs..ays '... solidly in the audiornonster amplifier class . .using 8 ohm loads ... THD was lessthan 0.01% for all power levels ... upto 200 watts .... '(per channel)' ... all inall we cannot imagine a less expensive way of obtaining several hundredwatts.' Yes, we, your friendly GAS company, have the goodscomplete with a fan for ultra cool operation. Available with direct read-' ing power meters in kit ($375) or fully assembled ($525). Also thesame amp but no meters in kit ($340) and assembled ($475). Write usfor complete specs, or read Popular Electronics, September 1974.Available directly fromTHE GREAT AMERICAN SOUND COMPANY, INC.8780 Shoreham Drive, West Hollywood, California 90069CIRCLE NO. 17 ON READER SERVICE CARDasNew Continental Specialties p ecialtfor QTSOCKETS® and BUS STRIPSSNAP /LOCK DESIGN offer expanded, flexible breadboardingwithout shorts orburnt fingers. Simply SNAP/C , LOCK together as manyQTs as you need and youcan test ICs, transistors,,r resistors, capacitors andIr more. Just plug -in, connecte" * e A with solid #22 AWG hookupwire - no soldering ore patch cords needed! And QTsare totally reusable. 10 differentsizes. Prices from $3 for QT Sockets... from $2 for Bus Strips.Write or phone today for FREE Selection Guide,with applications, photos, drawings, specs,socket sizes and ordering information.=M= Continental Specialties CorporationPAT. PENDINGithout solderingFREEMETRICTOENGLISHSLIDERULEConvertlengths, area,weight, volumeInstantly,Yours FREEwith minimum$5.00 order!44 Kendall St., New Haven, CT 06509, 203/624 -3103CIRCLE NO. 11 ON READER SERVICE CARDS406101

ISAVE!MONEY TIME FREIGHTQUALITY STEREO EQUIPMENTgl AT LOWEST PRICES.bt YOUR REQUEST FOR QUOTA-TION RETURNED SAME DAY.FACTORY SEALED CARTONS-GUARANTEED AND INSURED.s-SAVE ON NAME BRANDS LIKE:A.D,C,KLHA.R.SHUREDYNACOKOSSSONYFISHERAND MORE THAN 50 OTHERSBUY THE MODERN WAYBY MAIL -FROMilffnov audioDepartment 217S12 East DelawareChicago, Illinois 60611312.664 -0020CIRCI.18 ON READER SERVICE CARDjj* SAVE ONBrand Name AudioComponents102Write Today for OurFREE Audio CatalogDIXIE is one of the oldest and largest audio component mall order houses In the country. Our prices onbrand name components are actually LOWER then"Discounters". See our new catalog or call us for eprice quote. Everything shipped factory -sealed withfull manufacturer's warranty.,-for JW)h[.`..` -1;-,,KOfIE3a.eI.VO..F,...A.' ..-II.,I`Me.ter CHANT BenkAm.ncardtf.Honored on man order.eldllltìI BHUREFISHER....seKLHAllaINIIIIMILIL`-/LtL-+'`IeSONYDIXIE HI- FIDELITY!(n)'OARRARDWahlDVNACO5600 Second St., N. E., Washington, D. C. 20011Phone: 1. 202.835.4800Please rush me your FREE Audio Catalog andcomplete information. I understand there Is noobligation.NameAddressCityState Zip PEI!¿Ç'tkTONE CONTROL FOR BACKGROUND MUSICQ. I purchased a low -cost, general -utility, solid -state preamplifier andpower amplifier to supply backgroundmusic on my open patio. Now Ifind that I need some form of tonecontrol to get a better sound. Is therea simple way to do this?A. The tone control shown here canbe inserted between the preamp andthe power amplifier. You will have toget the power supply from theamplifier.ONE- TRANSISTOR PUSH -PULL OUTPUTQ. Is it possible to arrange a one -transistor push -pull output to drivetwo speakers -one in the emitter circuitand one in the collector?A. This circuit can be used to drive apair of 4 -ohm speakers with a 1 -wattoutput. Adjust the value of R1 to givethe voltage drops shown across thespeakers and the output stage.A ONE -TIME SWEEP GENERATORQ. I need some kind of r -f sweepgenerator to align the i -f of a receiverI built. I have no need for a commercialunit lust something simple forthis one -shot alignment.A. You could try the basic circuitshown here. The UJT output goes to330AHEP510yF47K500KRATEBCOPHOK100KHobby SceneIN+15/20v1595556 oI/BABAIM500KTREBLEthe horizontal (external) input of thescope; and you can set the desiredsweep rate with the potentiometers.The varactor can be any one in therange of about 50 pF. Use a Miller 9003coil with a range of 380 to 1000 kHz fora 455 -kHz i -f or a Miller 4505 (10 to 14MHz) for a 10.7 -MHz i -f. Other coilscan be used for other ranges.3,3KOIyF..000M-47pF2205F5100ERFOUTPOPULAR ELECTRONICSOUTELECTRONICS MARKET PLACEINON -DISPLAY CLASSIFIED: COMMERCIAL RATE: For firms or individuals offering commercial products or services, $1.80 per word (including name andaddress). Minimum order $27.00. Payment must accompany copy except when ads are placed by accredited advertising agencies. Frequency discount; 5% for 6months 10% for 12 months paid in advance. READER RATE: For individuals with a personal Item to buy or sell, $1.10 per word (including name and address.)No minimum! Payment must accompany copy. DISPLAY CLASSIFIED: 1" by 1 column (2 -1/4" wide), $215.00. 2" by 1 column, $430.00. 3" by 1 column, $645.00.Advertiser to supply cuts, For frequency rates, please inquire.GENERAL INFORMATION: First word In all ads set in bold caps at no extra charge. All copy subject to publisher's approval. All advertisers using PostBoxesOfficein their addresses MUST supply publisher with permanent address and telephone number before ad can be run. Advertisements will not bewhich advertisepublishedor promote the use of devices for the surreptitious interception of communications. Closing Date: 1st of the 2nd month preceding(forcover dateexample, March Issue closes January 1st. Send order and remittance to POPULAR ELECTRONICS, One Park Avenue, New York, New York 10016,Attention: Hal Cymes.FOR SALEFREEI Bargain Catalog- I,C.'s, LED's, readouts, fiberoptics, calculators parts & kits, semiconductors, parts.Poly Peke, Box 942PE, Lynnfleld, Mass. 01940.GOVERNMENT Surplus Receivers. Transmitters,Snooperecopes, Radios, Parts, Picture Catalog 25 cents.Meshna, Nahant, Mass. 01908.LOWEST Prices Electronic Parts. Confidential CatalogFree. KNAPP, 3174 8th Ave. S.W., Largo, Fla. 33540.ELECTRONIC PARTS, semiconductors, kits. FREE FLYER.Large catalog $1.00 deposit. BIGELOW ELECTRONICS,Bluffton, Ohio 45817.RADIO-T.V. Tubes -36 cents each. Send for free catalog.Cornell, 4213 University, San Diego, Calif. 92105.AMATEUR SCIENTISTS, Electronics Experimenters,Science Fair Students...Construction plans- Complete,Including drawings, schematics, parts list with prices andsources...Robot Man - Psychedelic shows - Lasers Emotion/Lie Detector - Touch Tone Dial Quadraphonic Adapter - Transistorized ignition -Burglar Alarm - Sound Meter...over 60 items. Send 25cents coin (no stamps) for complete catalog. TechnicalWriters Group, Box 5994, University Station, Raleigh, N.C.27807.METERS -Surplus, new, used, panel or portable. Send forlist. Hanchett, Box 5577, Riverside, CA 92507.WE. SELL CONSTRUCTION PLANS. TELEPHONE:Answering Machine, Speakerphone, Carphone,Phonevision, Auto Dialer, Touch Button Dialer, CentralDial System. TELEVISION: $35.00 Color Converter, VideoTape Recorder. $25.00 Camera. HOBBYIST: ElectronMicroscope, 96 Hour Tape Music System, Ultrasonic Dishwasher,Radar -Oven, Plans $4.95 each. NEW ITEM: $75.Electronic Pocket Calculator, $7.50. COURSES: TelephoneEngineering $39.50. Detective Electronics $22.50,Integrated Circuit Engineering, $49.50. NEW SUPERHOBBY CATALOG plus year's subscription to ElectronicNews Letter AIRMAILED $1.00. Don Britton Enterprises,6200 Wilshire Blvd., Los Angeles, Calif. 90048,LOOKING FOR A NEW CHALLENGE?-.. then bulkl a TV camera/ONLY SOLID SIATECAMERA AVAILABLE IN NIT FORMOR FACTORY ASSEMBLED COMPLETE KIT WITH VIDICON TUBE OAK V 116500 POSTPAID DELIVERY ANYWHIR( IN USA. CANADA and MEXICO. OPTIONALAUDIO SUBCARRIER SIB 95 WRITE or PHONE NOWFOR COMPIETE CATALOG OF NITS, PARTS .std PLANS0,.1 401 981-31711301 oowMrAT ATV Research oAMOsA CITY NUR. auralDIGITAL ELECTRONICS: Complete schematics,partslists, theories - Discrete Component Digital Clock,$3.00 - Sound Sensitive Switch, $1.50. Increase technicalcompetence, hobby skills - Complete Course in DigitalElectronics Is highly effective, $10.00. Free literature.DYNASIGN, Box 60A7, Wayland, Mass. 01778.MECHANICAL, ELECTRONIC devices catalog 10 cents.Greatest Values - Lowest Prices. Fertik's, 5249 "D ",Philadelphia, Pa. 19120.SOUND SYNTHESIZER KITS -Surf $12.95, Wind $12.95,Wind Chimes $17.95, Electronic Songbird $6.95, MusicalAccessories, many more. Catalog free. PAIA Electronics,Box J14359, Oklahoma City, OK 73114.DISCOUNT PRICESB & K, SENCORE, LEADER and RCATest EquipmentRAYTHEON, ICC/MULLARD TubesTELEMATIC Test JigsFree CatalogFORDHAM RADIO SUPPLY CO., INC.558 Morris Ave. Bronx, N.Y. 10451FREE CATALOG. Parts, circuit boards for POPULARELECTRONICS projects. PAIA Electronics, Box C14359,Oklahoma City, OK 73114.JANUARY 1975CONSTRUCTION PLANS: Laser...$2.00. Rocket TrackingTransmitter... $2.00. Space Monitor -MissileTracker...$2.00. Free Catalog, Electro- Research, P.O. Box20285, Ferndale, Michigan 48220.CD IGNITIONS, VHF /UHF monitors, crystals, CB radios,Southland, Box 3591 -B, Baytown, Texas 77520.PAIA ELECTRONICS, INC.SOX P14369, OKLAHOMA CITY, OK 73114BUGGED ? ?? New locator finds them fast. Write, Clifton,11500 -L N.W. 7th Avenue, Miami, Florida 33168,TELEPHONE "BUGGED "? Countermeasures Brochure$1.00, Negeye, Drawer 547, Pennsboro, W. VA 26415.HEAR POLICE/FIRE Dispatchers) Catalog shows exclusivedirectories of "confidential" channels, receivers. Send 10cent stamp. Communications, Box 56 -PE, Commack, N.Y.11725.CONVERT any television to sensitive, big- screen oscilloscope.Only minor changes required. No electronicexperience necessary. Illustrated plans. $2.00. Sanders,Dept. A -33, Box 92102, Houston, Texas 77010.YOU WILL SAVE BIG MONEYI Surplus, Clearouts,Bankruptcy, Inventory, Deals. Catalog $1 (redeemable),ETCOA Electronics, Box 741, Montreal, H3C 2V2. U.S.Inquiries.BURGLAR -FIRE alarm supplies and information. Freecatalog. Protecto Alarm Sales, Box 357 -G, Birch Run,Michigan 48415.COMPLETE CONSTRUCTION PLANS -TELEPHONE:Answering Device. Automatic Dialer, "Black Boxes ", CallDiverter, Call Limiter, Conference Bridge, Central DialExchange, Melodic Ringing, RecorderActuator, RemoteControl, Schematics, Speakerphone, Telelink BurglarAlarm, Voice Scrambler, $3.00 each. ELECTRONIC:Biofeedback Conditioner, Horticulture Stimulator,Multifrequency Encoder Network (Speeds telephonecalling 100%I). $5.00 each, ONE YEAR SUBSCRIPTION:Telephone -Electronics Newsline $3.00. Super Illustrated 16page catalog of plans, many more, 50 cents. All of theconstruction plans above, $19.95. TELETRONICSCOMPANY OF AMERICA, P.O. Box 3486, Hollywood,California 90028. USA.PRINTED CIRCUIT TECHNIQUES for the Hobbyist,Booklet: $2.00. Trumbull, 833 Basra Drive, El Cerrito, Calif.94530.h INTERNATIONAL ELECTRONICS UNLIMITEDTTL7400 5 .19 7474 S .437401 .19 7475 .457402 .19 7476 .477403 .19 7483 1.117404 .22 7486 .447405 .22 7489 2.757406 .39 7490 ,767407 .39 7491 1,297408 .25 7492 .797409 .25 7493 ,797410 .19 7494 .897413 .79 7495 .897415 .39 7496 ,897416 .39 74107 .497417 .39 74121 .577420 .19 74123 .997423 .35 74125 ,697425 .39 74126 .797426 .29 74141 1 237427 .25 74145 1.157430 .22 74150 1.097432 .29 74151 .897437 .45 74153 1.297438 .39 74154 1.597440 .19 74157 1.297441 1.09 74161 1.397442 ,99 74163 1.597443 .99 74164 1.897444 1.10 74165 1.897445 1.10 74166 1.657446 1.15 74173 1.657447 1.15 74177 .997448 1.15 74180 1.097450 .24 74181 3.657453 .27 74182 .897454 .39 74190 1.597460 .19 74193 1.397464 .39 74194 1.397465 .39 74195 ,997472 .36 74198 2.197473 -43 74199 2.19Dale .h..n.uPPII.d on r.Au.nsso for Nom. L.. then s1.00CMOS74C00 S.39 74C42 2.1574C04 .75 74C76 1.7074008 .75 74C173 2.90M74C10 .65 80C97 1.504000 SERIES RCA- EQUIV,CD4001 S .55 CD4017 2.95CD4009 .85 CD4019 1.35CD4010 .85 CD4022 2.75CD4011 .55 CD4023 .55CD4012 .55 CD4025 .55CD4013 1.20 CD4027 1.35CD4016 1.25 CD4035 2.85 `LINEAR CIRCUITS301 Hi pert, op amp mDIP S .32307 Op amp wOlF .35308 Micro -pwr op amp mDIP 1.10309K 5V reg 1A TO-3 1.65311 Hi pert. V comp mDIP 1.05319 Hi -speed dual comp DIP 1.29324 Quad op amp DIP 1.95339 Quad comp DIP 1.69340T Pos V reg (5V, 6V, 8V,12V, 15V, 18V, 24V) TO.220 1,95380 2w audio amp DIP 1.49380 -8 .6w audio amp mDIP .89381 Lo noise dual preamp DIP 1.79550 Prec. V reg DIP .79655 Timer mDIP .99660 Phase locked loop DIP 2.75565 Phase locked loop DIP 2.65709 Op amp DIP .29723 Volt reg. DIPg'.69741 Comp, op amp mDIP .35747 Dual 741 DIP .79748 Fregadj 741 mDIP .391458 Dual Comp op amp mDIP 693900 Quad amp DIP .653905 Prec. timer DIP .658038 Function gen. DIP 5.9575451 Dual prl. driver mDIP 3975452 Dual pr. driver mDIP .3975453 Dual prl. driver mDIP ,3975491 Quad seq driver DIP .7975492 Hex dig. driver DIP .89Om. ewe. .,,PPII.d nn .n.",Add 1.50.., Items Inn m.n 51.00'CALCULATOR & CLOCK CHIPS w /data5001 12 DIG 4 funct fix dec 3.955002 Same as 5001 exc btry pwr 7.955005 12 DIG 4 fund w /mem 8.45MM5725 8 DIG 4 fund chain & dec 2.79MM5736 18 pin 6 DIG 4 funct 4.95MM5738 8 DIG 5 funct K & Mem 7,95445739 9 DIG 4 fund (btry sur) 6.95MM 5311 28 pin BCD 6 dig mux 6.95MM 5312 24 pin 1 pps BCD 4 dig mux 6.95MM 5313 28 pin 1 pps BCD 6 dig mux 7.95MM 5314 24 pin 6 dig mux 8.95MM 5316 40 pin alarm 6 dig 8.95IseWNW'JANUARYSPECIALS7406 Hex inverter S .357440 Dual 4 input butter .177454 And-or- invert gate .237474 Dual D flip flop .2974125 T.S. quad buffer .5674175 Quad D flip flop 1.808230 T.S. 2 -4 line mux 1.958830 Dual lino driver 1.758836 Quad 2 input rec. .25301 Hi pert. amp .19380 2 w audio amp 1.353900 Quad amp .391103 1024 -bit dyn. Ram 2.955316 6 dig. alarm clock 6.95ALL DUAL -IN -LINEMEMORIES1101 256 bit RAM MOS $1.751103 1024 bit RAM MOS 4.955260 1024 bit RAM low power 3.957489 64 bit RAM TTL 2.758223 Programmable ROM 4.9574200 256 bit Ram -tri -state 7.95LED'S AND OPTO ISOLATORSMV10B Red TO 18 S .25 ea.MV50 Axial leads .20MV5020 Jumbo visible red .33ME4 Infra red diff, dome .60MANI Red 7 sog..270" 2.50MAN2 Red alpha nun. .32" 4.95MAN3A Red 7 sog..127" .79MAN3M Red 7 seg..127" claw 1,15MAN4 Red 7 sog..190" 2,15jMAN5 Green 7 reg..270" 2.95MAN7 Red 7 sag..270" 1.35MAN8 Yellow 7 sog..270" 3.95MAN66 60" high dir. view 4.65DL707 Red 7 sag. .3" 2.15MCD2 Opto -iso diodes 1.09MCT2 Opto -iso transistor .69ON ORDERS OVER $25.00 DEDUCT 10%All items are new, unused surplusparts - tested functional.Satisfaction is guaranteed. Shipment will be made via first class" " "1° mail - postage paid - in U.S., Canada and Mexico within threedays from receipt of order. Minimum order - 55.00. Californiaresidents add sales tax.1408) 6594773 INTERNATIONAL ELECTRONICS UNLIMITEDP.O. BOX 1705 MONTEREY, CALIF. 93940 USACIRCLE NO. 19 ON READER SERVICE CARD\4103

,$2.95CRYSTALS, Scanners, $3.88, include make and frequency.G Enterprises, P.O. Box 461PC, Clearfield, UT 84105.FREE CATALOG. Kits. Components, audio equipment.Electronic Supply Pacs, Box 175, Floral Park N.Y. 11001.PRACTICAL Applications of Digital IC's. 100's of tips,circuits, projects, on TTL. 443pp $19.95. Money BackGuarantee, GEA, P.O. Box 285 Northfield, Ohio 44067.ALPHA/THETA BRAINWAVE biofeedback instruments.Analog instruments from $125; digital processing systemsfrom $225. BioScan, Box 14168 -E, Houston. Texas 77021.SURPRISE! Build inexpensively, the most Unusual TestInstruments, Futuristic Gadgets using NumericalReadouts! Catalogue Free! GBS, Box 100A, Green Bank,West Virginia 24944.ELECTRONIC ORGAN KITS. KEYBOARDS and manycomponents. Independent and divider tone generators. Alldiode keying. I.C. circuitry. Supplement your ArtisanOrgan, 35 cents for catalog. DEVTRONIX ORGANPRODUCTS, Dept. C., 5872 Amapola Dr.. San Jose. Calif.95129.ELECTRONIC IGNITION: Capacitor, transistor. pointless.Auburn sparkplugs. Information 10 cents. AndersonEngineering, E Epsom, N.M. 03234.WHOLESALE Scanners, CB, Crystals, Directories,SSB /AM, Catalog 25 cents. G- Enterprises. Box 461P,Clearfield Utah 84105.CALCULATOR OWNERS: Use Y ou r c alculator tocompute square roots, trigonometric functions, logarithms,and more! Quickly, Accurately, Easily! Send today for theFirst and Best Calculator Manual ... now in use throughoutthe world ... still only $2.00 Postpaid with UnconditionalMoney -Back Guarantee! Malimann Optics andElectronics, Dept. 23A, 836 South 113, West Allis,Wisconsin 53214.FREE 1975 Electronics Catalog. McCord Electronics. Box276-N, Sylvania, Ohio 43560.AUTORANGING DMM, deluxe VOM's, logic probes andmore. Lowest prices. Free catalog. Electro Industries, 4201Irving Park, Chicago, Illinois 60641.ARE YOU PREPARED? 10,000 cubic toot, pull ring ignitedemergency smoke grenades are now available! 3 for $7.50.9 for $20.00. Postpaid. Pacific Aero Supply, Box 601,Malibu, Calif. 90265.PYROTECHNICAL chemicals, casings, tools, supplies,tuse. Price List 50 cents. Westech, Logan, Utah 84321.TELEPHONES UNLIMITED, equipment, supplies. Catalog50 cents. Box 1654E, Costa Mesa, Calif. 92626.740074017402740374047405740674077408740974107411741274137416741774187420742174237425742674277429743074327437743874397440744174427443744474457446744774487450745174537454745974607470747274737474104$ ,g T T L 74184 2.30.19 7475 .75 74185 2.19.19 7476 .47 74187 6.00.21 7480 .50 74190 1.50.22 7482 1.75 74191 1.50.39 7483 1.11 74192 1.35.39 7485 1.10 74193 1.35.25 7486 .44 74194 1.39.25 7488 3.00 74195 .95.19 7489 2.75 74196 1.25.29 7490 .79 74197 .99.40 7491 1.29 74198 2.19.79 7492 .79 74199 2.19.39 7493 .79 74200 6.95.39 7494.25 7495.19 7496.35 74100.35 74107.39 74121.29 74122.35 74123.40 74125.22 74126.29 74141.45 74145.39 74150.50 74151.19 741531.08 7415499 74155.99 741561.10 741571.10 741601..10 741611.10 741631.10 74164.24 74165.89.27 74166 1.65.27 74170 3.00.39 74173 1.65.25 74174 1.85.19 74175 1.85.45 74176 .89.36 74177 .89.43 74180 1.05.42 74181 3.5020% Discount for 100Pieces Combined 7400:89 CMOS.89 CD4001 $ .551.50 CD4002 .55.47 CD4007 1.25.55 CD4009 .85.47 CD4010 .65.99 CD4011 .55.60 CD4012 .55.79 CD4013 1.10.15 CD4016 1.25.10 CD4017 2.50.05 CD4019 1.25.89 CD4020 1.50.29 CD4023 .55.25 CD4025 .55-19 CD4027 1.2529 CD4030 .6029 MC3022 2.00.65 74C00 .3539 74C04 .69.59 74C20 .65.89 74C173 2.508000 SERIES8091 .598092 .598095 1.398123 1.598130 2.198200 2.598210 3.498223 4.008288 1.158520 1.298826 5.008880 1.33CARBON FILM RESISTORS. Brand new as low as 2 -1/4cents. FREE samples and specifications. COMPONENTSCENTER -PE, Box 134, New York, NY 10038.7,000 SEMICONDUCTORS. 100's Electronic Circuit Kits,Technical Reports, Energy Conservation, Computers. Cat.50 cents. E/S Lab, Box 738, College Park, MD 20740.UNSCRAMBLERS: Fits any scanner or monitor, easilyadjusts to all scrambled frequencies. Only 4 square$29.95. fully guaranteed. Dealer inquiries welcomed. PDOElectronics, Box 841, North Little Rock, Arkansas 72115.LEARN DESIGN TECHNI QUES. Electronics Month) YNewsletter. Digital, linear construction projects, designtheory and procedures. Sample copy $1.00. Valley West,Box 2119 -B, Sunnyvale, California 94087.BURGLAR -FIRE ALARM components,hardware. FreeCatalog -Information. Silmar, 133 S. W. 57 Ave., Miami,Florida 33144.WE SELL MONEY MAKING CONSTRUCTION MANUALS!!!- Reclaim GOLD, SILVER for EXCELLENT full or part timemoney!!! - PLUS, we buy scrap gold 8 silver - ALSO, wesell 99.999% pure SILVER BARS!!! - Color Catalog 25cents - Airmailed 50 cents - Creative Products, Dept.PE-175, 4913 Northridge NE, Albuquerque, New Mexico, 987111.DIGITAL IC Manual- Latest Edition -1500 types bytypes /diagram number $3.95. 32- function digitalcomputer kit -IC transistors, instructions, $14.00. ICapplications manual-numerous circuits-Analog/Digital,$3.95. Electronetics, P. 0. Box 127. Hopedale, Mass. 01747.ALPNAITIIETA BRAINWAVEi1'. t .`-BIOFEEDBACK INSTRUMENTSThe only biofeedback instruments availablewith powerful built -in digital processing.AlphaScan 400 shown at $225;others from $125 -$795. Write for freeliterature including our booklet, "SomeTechnical Considerations for EEG Biofeedback Instrumentations."BioScan Corporation, Box 14168 -E, Houston,Tex. 77021" ELECTRONIC INSTRUMENTATION FOR THE LIFE SCIENCES"ELECTRONIC COMPONENTS -all kinds, send for freecatalog. Epic, Box 20152A, Minneapolis, Minn. 55420.QUALITY military and industrial surplus electronics. Send25 cents for last 3 of our monthly picture flyers. US only.Startronics, Box 17127, Portland, OR 97217.COMPUTER SCHEMATICS. 256 bits, expandable toseveral K. Many other schematics available. SPElectronics, Box 5E, Prospect Heights, Illinois 60070.Christmas SPECIALSDigital LCD WatchLiquid Crystal DisplayConstant on -Shock Proofuses Field effect displayAccuracy to 1 Minute -a -Year.FREQUENCY COUNTER for under $75.00; provisions to200MHz, Nixie or LEO readout 8 digit; uses standard IC's,complete details $3.00, postpaid. East Coast Electronics,50 Scott, Hamburg, New York 14075.COMPUTER countless uses. 8 bit word, powerful instructionset. Complete $225. Brochure 10 cents. RAECO, Box14, Reedville, Mass. 02137.TEN Batteries 1 -1/2V. Send $2 for batteries and price list.Electronics, Box 33071, District Hts., MD 20028.ELECTRONIC SURPLUS 1974 Catalog 25 cents. Refundablew,krder. Atlantis, Box 12654P, Tucson, AZ 85711.6 a5 Year Warranty $149.95eaUnassembled Kit 99.95eaCalifornia Res. Add 6% TaxUSA MADECALCULATORS5m8 -4 Function 9V $29.956 Month Warr. Red Led eaSL8M -4 Function Memory $53.00%-Add on Disc. -Tilt Lens ea5m -20-5 Function Memory $39.95Constant -9V -1 Yr.W.eaTIME -Temp Display6 digit LED DisplayLiquid Crystal Temp. Display115 Volt -1 Yr. Warr. $39.95IC sockets-Kit from $29.958 pin DIL .22 36 pin DIL 1 .70 PROJECTS14 pin DIL .26 40 pin DIL 1.90 8263 $ 7.0016 pin DIL .29 WIRE WRAP 8267 4.0018 pin DIL .46 LEVEL #3 2513 12.0022 pin DIL .65 14 pin DIL .46 2518 7.0024 pin DIL .68 16 pin DIL .55 2524 6.0028 pin DIL .99 24 pin DIL 1.05 7805 2.00Satisfaction Guaranteed. All Items 100% Tested$5.00 Min. Order - 1st Class Mail - No ChargeCalifornia Residents - Add 6% Sales TaxWholesale Outlets - Write for Special DiscountsWrite for FREE Catalog - Data Sheets .20d eachP.O. BOX 822, BELMONT, CA 94002ORDERS (415) 592 -8097CIRCLE NO. 20 ON READER SERVICE CARDSUBSCRIBE NOW: miLEARN THE SECRETS OF YOUR TELEPHONEl.d:.' r. " .,.Eh!Etronìts tineFACTS NEVER PUBLISHED FOR THE PUBLICt A UNIQUE REFERENCE GUIDETO THE INSIDE STORY1 FROM THE HOBBIEST S TO O THE TECHNICIANCurrent News Item s Plans IllustrationsSto r' es HistoryComics Gamest Code Numbers Projects And Many More1 One year subscription only S 3.00 -COMPANY C5 "2,41a' T C MI L S8AÑGÉ G,CA.EMMDESCRAMBLERS several models that work with allscanners and tunable receivers, Automatic ActivatedPhone Patch, Proximity Alarm Kit, Telephone ScramblerKit, Tone Signaling Kits, Jinni -1 Semiconductor Tester withLED readout indicators, other kits, parts, plans. Catalog 25cents, KRYSTAL KITS, Box 445, Bentonville, Ark. 72712.ELECTRONICS parts, low prices, free flyer: DARTEKELECTRONICS, Box 2460, Dartmouth, Nove Scotia,Canada. U.S. Inquiries.WHOLESALE BURGLAR ALARM supplies. Catalog $1.00(refundable). Elfin, 161W Boned, Chestnut Hill, Mass.02167.ELECTROENCEPHALOPHONE/Brain activity control. Z.J.Daszewski Lab., 361 Garretson Ave., Perth Amboy, N.J.08861. Tel: (201) 826 -3061. Please send 25 cents or self -addressed envelope with inquiry.LM300 LINEAR $ .79LM301H /N .30LM302H Voltage Follower .75LM304H Negative Volt Reg 1.10LM305H Positive Volt Reg 1.00LM307H /N Op Amp (Super 741) .35LM308H /N Micro Power Op Amp .99LM309K 5 Volt Regulator /Amp 1.25LM310H Improved Volt Follwer 1.35LM311 H/N Hi- perform Volt.Comp. .89LM318N Hi -Speed Op Amp 2.00LM320K To 3 Neg. Regulator 1.50LM324N Quad 741 Op Amp 1.75LM339 Quad Comparator 1.65LM340K Positive Volt Regulator1.89LM370N A 6 C - Squelch Amp 1.55LM373N AM /FM $$ B Strip 3.30LM380N 2 Watt Audio Power Amp 1.15LM555N Timer .75LM565- LM566 -LM567 Phase L.L. 2.00eaLM703H RF /IF Amp .45LM709H /N Op Amp .29LM723H /N Voltage Regulator .55LM741H/N Comp. Op Amp .30LM747H /N Dual Compen.Op Amp .79LM748N Freq. Adj. 741 .40LM1310P Stereo Demodulator 3.50LM1458N Dual Comp. Op Amp .65LM1556N 5 Times Faster 741 1.85LM2307P Current Controlled 05 Cil. 3.15LM3065N T.V. -FM Sound System .75LM3900N Quad Amp .50LM3905N Precision Timer .65LM7522 Core Memory Sense Amp. 2.50LM7524 Core Memory Sense Amp. 1.50LM7535 Core Memory Sense Amp. 1.00LM75451 Dual Peripheral Driver .49LM75452 Dual Peripheral Driver .49LM75453 Dual (LM351) .65LEDSMV10 5/1MV50 6/1MV5024 5/1MAN -1 1.95MAN -3 .95MAN -4 1.95MAN -7 1.00DL33 1.95DL747 2.50POWER SUPPLY KITSVariable Power Supply5 to 25 Volt Ampg1FIXED POWER SUPPLY it1 Amp - Specify one of theten available voltages plusPlus Voltage: 5- 6- 12 -15 -24Minus Voltage: 5- 6- 12 -15 -24Less - Chassis $16.95 per Kit'L-h11READOUTS"ALL LED" MONSANTOMAN -1MAN-3 a" MAN.6. 7fß MAN -64MONSANTO CHAR. SALE QuantityTYPE HT. EACH DiscountsMAN -1 .27 $3.50 3 for $ 9.MAN -2 32 4.95 3 for_O MAN -3 .12 1.00 3 for $ 2.50MAN -6 .60 4.50 3 for $12.MAN -64 .4 3.50 3 for $ 9.MAN -7 .27 1.50 3 for S 335 LED matifWRISTWATCHLIQUIDCRYSTALDISPLAYNATIONALLINEAROP AMPSLM-309K 1.50L4-319 1.19LM320 1.25LM-340 2.50LM-380 1.39LM3e1 1.69LM-703 AlLM-703M .41LM-709 .25LM-710 .29LM-711 .29LM-723 .61LM-725 .69LM-733 1.75LM-741 .31LM-741CV .31LM-I303 79LM-1304 1.10LM-1307 .79LM1458 .69LM-1496 .99LM-3028 1.50LM-3900 .49LM-4250C 2.10555 .88562 2.50565 2.50566 2.50U 567 2.85RC4195 2.504136 1.96555TIMERS2 a Secondsto 1 -hr.(Mini DIPI2 for $LSale good tillFeb. 15, 1975AM -FM-MULTIPLEXAMPLIFIERWITHESCUTCHEONJANUARY 197520 -Years of BusinessINTEGRITYao -Years of Money-Backae -Years ofmy!LOWEST PRICES!48 -HR. SERVICE3%2 digit, 7- segment -` v 59.95 only 1 1 /16 x 11/16 s1/4 ". Includes readout,socket, slide -in -placechrome slide face plate ".Same display as found in$200. units.529.95Buy 3 for $75.6DIGITDIGITAL 1 111 1111IFire First time m e ever offered! Mini design makes sto about thisanyunitroomschool.at home, office,Uses famouslab shop,Nationalspitclockcwtchips. GoldanEasyaaiaeato read numbers.sitive hive switches,Three pleasurefor HOLD,sen-HOURS,hours inSECONDSrear of12unit.or 24THISwiredIS NOT Aready toKIT! Completelygo. Size: 5 it 2instructionx It /aguide°. Gift boxed.booklet.WithWt. Vacycle operation.lb., 110 /VAC, 6035 WATT AUDIO $3.98AMPLIFIER BASIC Z for $7For Class AB use. Basic includes: Signet,e540 30 transistor high power driver TO -5"IC ", with pair of complimentary 35-watt plastic transistors, i.e. 255296 npnand 2N6109 pop. With schematics, printedcircuit and parts board layouts.BRAND NEW LOWEST PRICESGENERAL ELECTRIC 3 -WATT $2.50AUDIO AMP 3 FOR 36.00Rehvers :1.5 watts . 10 watts peak. wanheat inks; m micro-mini si a ua /cat/sat/a ". 9 to 30V supply.High sensitivity. 8 to 18 ohm..CLOCK CHIPS an Low as $6.99ON A "DIP" WITH DATA SHEETSMM5311 6 -digit 28 -Pin $6.99U MM5312 4 -digit 24 -Pin 6.99MM5313 6 -digit 28 -Pin 6.99MM5314 6 -digit 24 -Pin 6.99MM5316 4 -digit 40 -Pin, alarm 6.99MM5316 -A no alarm 3.95CT7001 4 -6- digits 9.95Alarm O Calendar60 -WATT STEREOAMPLIFIERAli Solid State, Prinbd circuitrySlid* Rule DIMAll Purpose, All Fenely Srst.,nlFeatures: 4-speaker system, built -inFM antenna. record player Jacks on separate panel.Another external panel consiste of provisions for externalFM and AM antenna, "satellite" speakers toprovide 4- speaker ground, jacks for connecting e taperecorder to radio tuner or phono of systems to record.Lower inputs for connecting tape deck that will playback thru the internal amplifier for systems. AC jack forphono power connection. RED. GREEN and CLEAR indicatorsfor Phono, AM, and FM respectively. Includesred indicator on front panel for STEREO indicator.Has separate input to plug into mike, guitar and othermusical instrumente as well Rs another jack for pluggingin a pair of stereo headphones.Has controls on front panel. PHONO-STEREO-AM-FM. MONO, FM STEREO. GUITAR. TAPE,MIKE master control switch. LOUDNESS, BALANCE.TREBLE, BASS controls. with power ON -OFF rockerswitch, and AFC ON -OFF. Designed for all audio- philesto r e as wall unit DEN or FAMILY ROOM, or con-trol s unit by easy chair in family room, or for thosewho wish to design their own console r modular system.With 6 ft. 115 VAC cord and plug. Only 13 s7 x 31 /a" deep. No escutcheon. but we include templater u e r e, plus diagram. Slips. wt. 3 lbs. With knobs.4 WATT GUITAR AMP SOLID ATEWith Tremolo$7.95 AMPEREXMusical instrument amplifier at low, low price! Peakpower output 10 watts. Two input circuits are qual-ised for normal or solo guitar. The four controls areVOLUME. TONE. TREMOLO INTENSITY and TREMOLOSPEED. There are terminals on board for normally openfoot switch connection. Supply voltage 18vdc. Outputto 8 ohm hi- quality speaks Input impedance 33,000ohms. Current drain 20 mils. External power supplyrequired. Wt. 1 Ib. With instructions, hookups anddiagrams. Sise 8 x 2% x 3.60 -WATT STEREOHIGH FIDELITY ,AMPLIFIERTape, Record Placer. PAMusical Instruments)The most amazing audio offer for the hi -fi -ers. PA men,an ideal unit for the family den. or any room in thehouse, office, etc. Comes complete with hookup, esculehron, and knobs. 5 separate controls: LOUDNESS.BALANCE, TREBLE, BASS. circuits switch for PHONO.TUNER. TAPE. SAKE, AUX. 3 switches for SCRATCHFILTER. RUMBLE FILTER. and POWER "ON -OFF" withbuilt -in lite. 4- output transistors, each 30 watts. Separateaccessory mounting panel for 4 speaker attachment,mike and musical instrument jack, tape, tuner.and power jacks. 6 -ft, cord set for 115VAC. 60 cycles.Measures only 1:1 x 7 x :i ". Wt. 3 lbs. With attractivemulti-color escutcheon. Made by leading US maker.20. 20.000 Cycles Resp 4- Channel Spkr. Systems!._mReslstorsKsyboereDrivers' a rra ayCase(PC boardsGET KEY THE PARTSCalculatorBasicMAKE SOUR OWNCALCULATORSWITH OURLOW PRICED6 -8 -12DIGITBASICSCHIPlo a.nrjCASEKEYBOARDCIRCLE NO. 30 ON READER SERVICE CARDribTHREE QUARTERINCH DIGITSBY OPCOA3 for 513.O to 90.7 character7 Segments30 milsOrder byTypeColorSLA -3H REDSLA -4H' REDS L A -13 GREENu(] SLA -14 YELLOSLA -23 YELLOWSLA -24 Y eELLOW*Plus or r Minus neTHE SIMPLEST! FINEST! SMALLEST!6- FUNCTION AC -DCCALCULATOR KIT!Lightweight. pocket size True credit balanceExtra large displaySimplified indexing6 functions plus, minus, Mark up and Mark downtimes. percentage, constant Constant multiplicationFloating decimaland divisionChain and Mix calculations AC adaptor jackDesigned pecifically for Poly Paks under the Dalton.80 brand. a IMAGINE! only 21/2 x 1 x 45/2 ". Slides easilyinto your v est pocket, p brief case or het handbag. ta Weeverywhere omany find calculator kit that canbe small, do the f BUILD! with fine engineeringdesign and SIMPLE TO WHY? Because it hashan the et parts in s a kit, kit. Imagine the pc two onlyhas the chip, 4 two two driveric's with the 9 digit repacked SIMPLE! SIMPLE] Yoo bet it isThe entire kit ' packed in eKit box that in itself tells the mini calculatorfor Kit (types: attractive black case a with wrd red dfilter; Flex (type 20 h8) w key keyboard ONmeasuresonly o r x with2 switches, one for ON-OFF, one o for K constant; MAIN pc readoptfamous Cal Tech 26-pin calculatordigit' rray;two lo drivers; Hewlett Packard 9 digit array;jack;Jack; 9 Volt battery connector esiaryrs; two iogselsyback protective vo necessary wire ylugdy instructions. (Less 9 volt standard battery andAC adapter)EASIEST KIT TO BUILDI BASIC KIT 51 - includes case, all- function Flex kc:Keyboard, Cal Tech CT5002 calculator chip, 9 -dlgüAntex LED display with built -on individual magnifiers.D lus sheets.$16.95BASIC KIT 2 same Basic tl calculator@ 1 except Pchip is National 8-digit g MM6725. $16.95 $B ASIC KIT 53 - same as Basic 51 except calculai.chip is National 6 -digit MM5736 and 75492. $16.9512 DIGIT BASIC Jt4 - Key parta include: CT6001chip, 4 -3 digit readout., factory etched PC board, case,carryini 2- resistor networks, decimal switch.Wild Rover a Keyboard with ON -OFF switch diagrams.Sale $24.95o8 -DIGIT MINI CALCULATOR BASIC KIT 56 - world'ssmallest. Needs least amount of components to completekit. Includes CT -6030 chip, mini case, with lens, keyboard,with on -aft and constant switches & percentage.9 -digit array (Hewlett Packard). Includes diagrams.$19.95.8 -DIGIT "TEXAS INSTRUMENT" BASIC KIT j(7 -includes Texaskeyboard, 1x8149, standard 4- function.G'ith T -I calculator chip TMS -0128, p.c. board, case,lens. Microswitch (on -oft). 9 -digit ANTEX array; includesdiagram, 519.95.MINI CALCULATOR BASIC KIT d8 - 4- Function Sameas KIT 86 except less percentage and constant.Includes CT -6031 chip, 517.95.ANY CASE for above Calculator Basics $2.50 3 for $6CALCULATOR ACCESSORIESTexas Instrument Keyboard $6.95Wild Rover KeyboardP.C. Boards 'stated" In above kits$6.95$2.50AC ADAPTERS FOR CALCULATORSLOWEST PRICES1.2 VOCh4rg2A foroNic deBatterles .3 for 518.3 for $18.3 for S 6.3 for S 7.3 for 7.ON NATIONAL 'CALCULATOR CHIPS'CT 5001CT 5002CT sonsCT 5030CT 5031TMS-0128MM 5725MM 5736First,12- Digits, 40 pin $4.959 -Volt version of 6001 6.5012-Digits,memory 7.504- Function with % 9.954- Function Only 6.954- Function by Texas 9.956- Digits, 4- funct. LED 4.956- Digits, 28 -pin, 9V 4.953 for $12.3 for $18.3 for $21.3 for $24.3 for $18.3 for $24.3 for $12.3 for $12.ANY 101C'S BUY 100FROM OUR 2 PAD[ ADTAKE 15% TAKE 25%Inflation -Fi htingECONOMY IGA PRICESType Salo Order bv type number! Nper .heels on renue+. "ONLY" Factory MarkedSN7400 5.19 SN7430 .24 SN7472 t .42 SN74107 .49 U SN74161 1.59SN7401 .19 SN7432 .28 5N7473 .52 SN74108 .95 SN74163 1.75SN7402 .24 SN7437 .45 SN7474 .39 51474112 .95 SN74164 2.85SN7403 .19 SN7438 .49 SN7475 .91 SN74113 .95 SN74165 2.85SN7404 .27 SN7440 .19 SN7476 .52 SN74114 .95 SN74166 1.855N7405 .24 SN7441 1.00 5N7478 .79 SN74121 ,49 51474173 1.85SN7406 .79 U SN7442 1.00 5N7480 .59 SN74122 .55 SN74174 2.255N7407 .48 SN7443 1.00 SN7481 1.25 U SN74123 1.09 SN74175 1.99SN7408 .27 SN7444 1.00 SN7482 .99 SN74125 .65 SN74176 1.25SN7409 .27 5N7445 1.00 SN7483 1.19 5N74126 .89 0 SN74177 1.25SN7410 .19 SN7446 1.10 SN7485 2.50 SN74139 1.25 5N74180 1.1051417411 .31 5N7447 1.10 SN7486 .49 5N74140 2.50 5N74181 3.95SN7412 .55 5N7448 1.45 SN7489 2.95 5N74141 1.19 SN74182 1.055N7413 .89 5N7450 .27 U SN7490 1.81 5N74145 1.19 SN74185 2.34SN7414 2.25 SN7451 .28 SN7491 1.35 SN74148 2.95 5N74187 2.34SN7415 .45 SN7453 .28 U SN7492 .99 SN74150 1.19 Cl SN74192 1.59SN7416 .45 SN7454 .39 5N7493 .99 SN74151 .99 5N74193 1.59SN7417 .50 SN7455 .28 5147494 1.05 SN74153 1.39 SN74194 1.89SN7420 .22 U 5N7460 .26 SN7495 .99 51474154 1.69 SN74195 1.105N7421 .50 SN7461 .26 SN7496 .99 SN74155 1.29 SN74196 1.20SN7422 .29 U SN7462 .39 SN74100 1.55 5N74156 1.45 SN74197 1.10SN7423 .32 U 5147464 .39 SN74104 1.25 5N74157 1.45 SN74198 2.45SN7425 .35 51417465 .39 5N74105 .95 5N74158 1.45 SN74199 2.455N7426 .31 C 5N7470 .49 SN74106 .95 SN74160 1.85 SN74200 7.50SN7427 .35 SN7471 .55INTEGRATED CIRCUITSOCKETSl'í4 -Pin, DIP 5.45L 14. Pin. Side Mount1-116.Pln,1.00DIP .50.JTO.5, 9 or 1O.Pins .29O Any y 3 T 8 -Ps enTake Y. IMinl DIP/14 -Pin, .39Discount!Wire Wrap16 -Pin,..699Wire Wrap 89eTerma[ add pontage Rated: net 30Phone Orders: Wakefield, Mass. (617) 245.3829Retails 16 -18 Del Carmine St., Wakefield. Mass.(oft Water Street) C.O.D.'S MAY BE PHONED20e CATALOG on Rber Optics, 'ICs', Semi's, PartsMINIMUM ORDER - $4.00POLY PAKSP.O. BOX 942E. LYNNFIELD.MASS. 01940105

$DIGITAL MODEM SYSTEMS, $45.00, IC's under 10 centseach, miscellaneous computer equipment. Send SASE forfree flier, MNH- Applied Electronics, P.O. Box 1208, Landover,MD 20785.RESISTORS 1/2, 1/4 watt 2 cents minimum $2.00. 5314clock chip $5.00, SLA -1 readouts $1.00. Lectronix, Box 42,Madison Heights, MICH 48071.FREE -Catalog of Electronic Surplus ComponentBargains. 10 cent stamp to TRI -TEK, Box 14206, Phoenix,AZ 85063.CONSTRUCTION PLANS. New projects every month. Sendfor complimentary copy. Electronic Projects Newsletter,Box 1026S, Fremont, Calif. 94538.CIRCUIT board service, Circuit boards made from yourlayouts. Send for information. Printed Circuits, 22 MapleAvenue, Lackawanna, New York 14218.FREE BARGAIN CATALOG. Transistors, LED's, Readouts,Micro -Miniature Parts, Unusual Electronic Components.Chaney's, Box 15431, Lakewood, Colorado 80215.TELEPHONE OR OFFICE BUGGED ? ?? ...Learn How ToProtect Yourself. Details $1.00. SECURITY, Box 671, Westwood,New Jersey 07675.KEYBOARD, ASCII, $35.00; UART, $10.00, 2102 memories,$10.00, 1101 A, $2.20, some microprocessor parts. CMOSRCA CD4017, $1.00. Beckman, 1618 James, Syracuse, N.Y.13203.VIDEO 1/4" Tape System -Portable. AKAI VT -100 $700.00.ZELL, Box 17017, Euclid, Ohio 44117.3iNEW: ROTARY CIRCUIT LOCALIZERVisual Aid Disks- turning revealsvisual electrical effectsand explanations simultaneouslyof capacitor inductor and resistorcomponents.$4.50 a Sel -Condensed Elect. TheoryPe riCalcBos 523, San Francisco, CA 94101ALARM CLOCK CHIP MM5316, $6.50! HP5082 -7730 7 segLED, $1.50! 60 cents postage. BDJ Electronics, Tappan.New York 10983.WANTEDQUICKSILVER, Platinum, Silver, Gold, Ores Analyzed.Free Circular. Mercury Terminal, Norwood, Mass. 02062.PLANS AND KITSATTENTION AUDIO FREAKS!! ... Audio Processing Circuits... designs, kits, units. Laboratory tested designs forhobbyist through professional use -limiters, compressors,equalizers, phasers, mixers and more! Send now -$1.00(refundable) for complete catalog- CIRCUIT RESEARCHLABS, 3920 E. Indian School, Phoenix, AZ 85018.KITSUNIQUECANADIANE LECTRONICSCATALOGUE$1.00(refundable on 1st purchase)featuringSINCLAIR hi -fi modules and calculatorkits. We will include the new 32 -pageProject 80 hi -fi module constructionmanual.AMTRON electronic kits -over 100 types!Speaker kits and componentsAmerican enquiries welcome!OLaOSTOfl&Ol-ELECTROIIICS1736 AVENUE RD.,TORONTO,ONT.M5M 3Y7. DEPT. PEIFREE CATALOG. 200+ unique electronic projects. Biofeedback,acupuncture, morel Cimarron Labs, 4183ASpringfield St., Burton, Michigan 48509.-ittesa1rMIRÁCAL 0BURROUGHS PANAPLEXBURROUGHS PANAPLEX II 12 digit display BR13251is a multi- digit, segmented, thin panel display in a commonenvelope. Any or all digits may be used, along with periodsand commas. The characters are 0.25 ", and are ideal forany device requiring multiple digits, clocks, counters, calculatorsetc. Compatible with DTL, TTL & CMOS circuitryand chips. Display is neon glow discharge, orange color.We provide many pages of data & applications. Cost is lesstha 1.00 per digit. 1"x33/4" for 12 digit display.STOCK NO.F220 11.95 ea, 2/21.001060complete calculatorKITSALL PARTS, INSTRUCTIONS INCLUDEDSIMPLIFIED PC BOARD CONSTRUCTION12 DIGIT CAPACITY 5x3x1 SIZESELECTABLE DECIMAL. BATTERY OR AC8 digit display - $19.95, 9 digit -$22.95. NiCad power pack - $3.95AC adapter /recharger - $2.95Manual only - $2.00 (deductablefrom Kit). Shipping - $1.50WIZARD ELECTRONICS Dept PE -1P.O. Box 161 Agnew Santa Clara California 9505412 VOLT DC SIRENHard to find 12 volt DC SI RENideal for alarm systems or any12 volt auto.STK. No. F5219 11.95 2/20.00 fHeat sink assembly of 2 2N4904 PNP87 watt power transistor. Other transistoris complimentary to above. Specsare same as 2N3055 except Bveco is40 volts. All transistors mounted insockets. Distributor price of transistorsis 3.35 ea. Extra NPN xistors availablefor .75 ea.STOCK NO.F9034 assembly 3.50 3/9.00MINIMUM ORDER $5.00. Include postage, excess refunded. Newedition of our catalog now available.DELTA ELECTRONICS CO.BOX 1, LYNN, MASSACHUSETTS 01903Phone (617) 388-4705CIRCLE NO. 13 ON READER SERVICE CARDUSE your transistor radio as a sensitive direction finder.Great for emergencies. Complete plans. Guaranteedresults. $1.00. RADIO COMPASS, Dept. B, Box 606, WebbCity, Missouri 64870.TESLA COIL -40" SPARKS! Plans $7.50. Information 75cents. Huntington Electronics, Box 2009 -P, Huntington,Conn. 06484.HIGH FIDELITYDIAMOND NEEDLES and Stereo Cartridges at Discountprices for Shure, Pickering, Stanton, Empire, Grado andADC. Send for free catalog. LYLE CARTRIDGES, Dept. P,Box 69, Kensington Station, Brooklyn, New York 11218.SAVE 50 %. Build your own speaker systems featuring Nor -elco, Eminence and CTS. Famous brands from world's largestspeaker factories at lowest wholesale prices. Write forfree catalog of speakers and electronic accessories.McGee Radio Company, 1901 McGee Street, Kansas City,Missouri 64108.LISTEN TO SPECTACULAR 4CHANNEL SOUND!Expand your stereo to quadraphonic Hi -Fi.Build the VISTA Full Logic "SQ" Decoder.Latest CBS licensed circuitry using 3 IC's to provide Full Logic and WareMatching.Exclusively ours. Kit SQ-1 $37.50. Shipped prepaid in USA 6 CANADA.Send for information.PHOTOLUME CORPORATION118 East 2815 Street, New York. N Y 10016SHOTGLASS. As seen in Esquire. Glasscone ColumnSpeaker. $129.50 each. F.O.B. Moneyback Guarantee.TECHYON© , Box 1012, Roselle, Illinois 60172.MOVIE FILMS8MM -SUPER 8 -16MM MOVIES! Biggest Selection! LowestPrices! Free Catalog! Cinema Eight, Box PE, Chester,Connecticut 06412.ELECTRICAL SUPPLIES & EQUIPMENTPLATING Equipment, Portable Platers, Supplies and"Know- How." Build your own tanks for nickel, chrome,etc. Easy -to- install PVC liners. Rectifier components -allsizes. Schematics, parts lists, formulas, operatinginstructions for all plating. Guaranteed to save you 25 %-75%. Some good units for sale. Write for details. PlatersService Company, 1511 -PE Esperanza, Los Angeles, Calif.90023."eoie.ehot p.feoae.Let us know 8 weeks in advance so that you won'tmiss a single issue of POPULAR ELECTRONICS.Attach old label where indicated and print newaddress in space provided. Also include your mailinglabel whenever you write concerning your subscription.It helps us serve you promptly.Write to: P.O. Box 2774, Boulder, CO 80302, givingthe following information:rChange address only.Extend subscription. Enter new subscription.1 year $6.98Payment enclosed (1 extra BONUS issue)Bill me latertVIHdvGOAFFIX LABEL- i óL omEcOo)Add'I postage: $2 per year outside U.S., its poss. & Can.vóoPOPULAR ELECTRONICSC MOS1-9 10 up4000AE $ .55 .534001AE .54 .534002AE .54 .534004AE 5.90 5.904006AE 3.90 3.804007AE .65 .604008AE 3.60 3.304009A E .95 .944010A E .95 .944011AE .54 .534012AE .54 .534013AE 1.15 1.054014AE4015AE3.703.803.253.704016AE 1.15 1.054017AE 2.90 2.704018AE 3.20 3.054019AE 1.30 1.204020AE4021AE3.903.803.303.604022AE 2.75 2.554023AE .54 .534024AE 2.30 2.004025A4026AE.549.80.507.104027 A E 1.35 1.224028AE 2.95 2.754029AE 5.40 4.604030AE 1.25 1.054035AE 2.85 2.804040AE 4.60 4.404041AE 3.30 3.204042AE 2.95 2.854043AE 2.95 2.854044AE 2.95 2.854047AE 3.70 3.604048A E 1.50 1.404049AE 1.35 1.054050A E 1.35 1.054056AE 3.50 3.464060AE 5.20 4.904066AE 3.20 2.964069A E .85 .75SchottkySN74SO0N $ .80SN74502N .80SN 74503N .80SN74SO4N .80SN 74508N .80SN74510N .80SN74S11N .80SN74320N .805N74S30N .80SN74S32N .80SN74540N .80SN74S41N .80SN74564N .80SN74S74N 1.50SN74385N 6.10SN74586N 2.90SN74S112N 2.50SN745113N 1.50SN74S133N 1.00SN74S138N 4.50SN745139N 3.90SN745140N 1.00SN745151N 3.30SN74S153N 3.30SN745154N 3.40$N745157N 2.70SN745158N 3.00SN74S160N 6.60SN74S161N 6.60SN74S174N 4.75SN74S175N 4.00SN74S181N 11.50SN74S189N 5.10SN745194N 3.30SN74S195N 4.40SN74S251N 4.20SN 745253N 4.20SN74S275N 3.20$N74S258N 3.70SN74S260N .90SN745280N 5.70SN74289N 5.0093510 6.8093516 6.8093521 3.5093522 3.2093548 3.70HIGHSPEED TTL74HOON74H01N74H04N74H05N74H08N74H1ON74H11N74H15N74H2ON74H40N74H74N.34.49.36.38.44.44.44.38.39.36.69Waveform Generator KitFM Stereo DemodulatorXR1310 53.90Audio Amps7400N7401N7402N7403N7404N7405N7406N7407N7408N7409N741 ON7411N7412N7413N7414N7416N7417N742ON7421N7423N7425N7426N7427N7428N7430N7432N7433N7437N7438N7439N7440N7441ÁN7442N7445N7447N7448N7450N7451N7453N7454N7460N747ON7472N7473NI-Amp Rectifiers1N40011N40021N40031N40041N40051N40061N400710 100 1000$ 1.00 7.00 60.001.10 8.00 70.001.201.309.0010.0080.0090.001.40 11.00 100.001.50 12.00 110.001.60 13.00 120.00LM352: 6-15V, 1.15W, B52 1.60LM354A: 6-27V, 2.80W, 852 2.50TAA611912: 6-15V, 1.15W, 852 1.60TAA621Al2: 6-27V, 1.404, 852 2.00TBA641 B11: 6-18V, 2.20W, 40 3.00T8A800: 5-30V, 4.70W, 852 2.20TBA810AS: 4-20V, 2.50W 452 3.00T6A820: 3-16V, 0.75W, 4i2 1.70TCA830: 5-20V, 2.00W, 40 2.20TCA940: 6-24V, 6.50W, 80 4.40Power TransistorsBU204 3A 1300V $4.14BU205 3A 1500V 4.95BU206 3A 1700V 5.94BU207 6A 1300V 5.85BU208 6A 1500V 6.938U209 6A 1700V 8.642N512B $3.002N1136 1.502N1483 1.202N1534 1.002N1540 1.102N1544 .902N3053 .352N3055 .952N3375 5.502N3442 2.202N3730 1.702N3731 2.002N3732 1.502N3771 2.202N3772 2.302N3773 3.402N3789 3.002N3866 .952N4347 1.602N4348 2.002N4395 1.302N4427 1.102N5109 2.102N5322 .922N5323 .702N6099 .802N6101 .802N6103 .90SPECIFICATION'SHEEETS: 9.25 ea.$ .16.23.22.22.25.29.38.48.24.54.24.29.51.782.81.46.64.19.51.49.39.29.35.51.22.28.61.44.441.01.191.16.98.981.501.29.23.28.25.26.24.30.39.46XR205K Only $28.00Here's a highly versatile labinstrument at a fraction ofthe cost of conventional unit.Kit includes two XR205 IC's,data & applications, PC board(etched & drilled, ready forassembly) and detailed instructions.DUAL LOWNOISEOP AMPLM331 N:Vio = fimV11e= 1000nAlb = 2000nANoise = 1.5dB$2.20Di italWatchwith liquidcrystal display.Beautiful,reliable andaccurate.$149.00 plus$2.50 forshipping andhandling./ S 6E\ear:HYBRID D' ,Q °w` "AMPLIFIERSSI-1010GSI-1020GSI-1030GSI-1050G10W20W30W50W$ 6.909.9018.7025.90CalculatorLIMITEd QUANTITYS19.00MemoriesP1101A $6.90P1101A1 8.50P1402A 7.90P2102 15.00P3101 5.50P3101A 5.50MM6560N 5.00MM6561N 5.00DM8599N 5.0093403 5.00Decoded Read/Write RAMP1103 $6.20\YYrY\+Vb\PREMIUM QUALITY COMPONENTSWe've been buying and selling top quality components for nearlyten years. Our annual volume exceeds $3 million. We handleonly original parts, from the world's leading manufacturers andour customers include some of the largest and most quality -conscious companies.Now you can take advantage of our componentbuying skills and power and select from a broadrange of advanced circuits.Yr\^fr\NY VnY\ \VY\'\}\- .....44e0OVOC14$4.04$IC sockets TeflonSolder8 pin DI L14 pin DIL16 pin DI L24 pin DIL28 pin DIL36 pin DI L40 pin DIL7400N TTL7474N7475N7476N748ON7481N7482N7483N7484N7485N7486N74B9N749ON7491N7492N7493N7494N7495N7496N7497N74100N74105N74107N74108N74109N74110N74111N74114N74115N74118N74119N74121N74122N74123N74125N74126N74128N74132N74136N74141N74145N74147N74148N.38$ .68.59.661.211.011.013.012.49.492.99.751.40.84.841.29.88.882.501.45.54.48.91.91.71.9191.911.50.81.54.89.951.391.391.212.05.911.891.792.953.55.22.26.29.751.101.701.9074150N74151N74152N74153N74154N74155N74156N74157N74158N74160N74161N74162N74163N74164N74165N74166N74170N74173N74174N74175N74176N74177N74180N74181N74182N74184N74185N74190N74191N74192N74193N74194N74195N74196N74197N74198N74199N74200N74122N74251N74278N74293N74293N74298N3 pin TO -54 pin TO -56 pin TO -58 pin TO -510 pin TO -5Wire Wrap14 pin DIL .4016 pin DIL .45$ 1 14.752.251.121.631.491.491.191.541.501.351.501.501.891.891.982.551.791.521.501.691.692.493.851.192.892.292.892.891.491.391.35.992.392.392.594.485.051.751.752 95.92.922.55.55.65.901.101.40POWER TTL74LOON74L02N74L03N74L04N74L 10N74L20N74L42N74L47N74L51N74L73N74L 74N74L90N74L93N74L95N1024 BitPi-ChannelRAM5 34.34.39.39.34.391.622.60.34.74.891.621.741.62Model 4440A PORTABLE4% DIGITMULTIMETERFOR 5299.A 10 MHZCOUNTER OPTIONFOR $50..26028 $21.002602 -1B 25.007552CPE 21.007552 -ICPE 25.0093 L 0093L0193L0893 LO993L 1093L1193L1293L1493L 1693L1893L2193L2293L2493L2893L3493L3893L4093L4193 L 6093L6657 -909-Digit Display1/8" character heightcompact, thin PCpackagewide viewing angleDisPlaYsIISLA1 Red $2.25 216SLA11 Green 4.25 216SLA21 Orange 4.25 216SLA2 ±1 Red 2.25SLA12 ±1 Grn 2.25SLA22 ±1 Org 2.25SLA3 Red 7.50SLA4 Red 7.50XAN72 Red 2.50XAN52 Green 2.50OptoisolatorMCT2 1.45MV50 Red $ .301.501.603.201.802.80 COMPVER4.20 22.4 ERrYSCE1.801.703.203.501.501.802.803.704.004.206.506.503.002.70Interface ModulesCV1010Cv1o11ACY1020CY1021CV 10214C V 2018CV2137CY2218CY2236CV2237CY2735CV2737C V 3035CV3635lost'. Amp., Bipolar Input -Instr. Amp., Bipolar InputInstr. Amp., FET InputInstr. Amp., FET InputInstr. Amp., FET InputoVoltageRegulatorsLM100H $ 5,50LM104H 6.50LM105H 5.10LM105F 8.50LM109H 9.50LM109K 6.30LM200H 3.80LM204H 4.70LM205H 3.00LM209H 3.50LM209K 3.70LM300H .90LM300N 1.40LM304H 1.40LM305H 1.10LM305AH 1.40LM305N 1.20LM309H 1.75LM309K 1.95LM34O-05K 2.60LM340-06K 2.60LM340-08K 2.60LM340-12K 2.60LM340-15K 2.60LM340-18K 2.60LM340-24K 2.60LM723H 1.30LM723D 3.90LM723CH .80LM723CN .75L129 1.50L130 1.50L131 1.50SG4501T 2.20SG4501N 2.20DM8820NDM8820ANDM8830NDM8831 NDM8832N960096019602961496159616961796209621DAC, 8 Bit, 2 Quad MultiplyingDAC, 10 Bit, Low DriftDAC, 12 Bit, 2 Quad MultiplyingDAC, 12 Bit, Fast Settling,Low DriftDAC, 12 Bit, Low DriftDAC, 4 Digit BCD, Low CostDAC, 4 Digit BCD, Low DriftADC, 8 Bit, Sect. Counting,Low Cost4.006.504.505.005.001.301.302.003.003.004.503.003.503.00LED's.125 "dia.209 Red $.25209 Yellow .35209 Green .35.16Oedia.Red .25yellow .30Green .30.2OOedia.220 Red .25220 yellow .30220 Green .30LOW PROFILE226 Red $ .25226 Yellow .30226 Green .30.301115053 Red $.355053 Yellow .405053 Green .405053 Orange .40216 = M V50245053 = MV5053Linear ICsLM114HLM301 ALM301AMLM301ANLM302HLM302NLM306HLM307HLM307MLM308HLM308AHLM310HLM311 HLM318HLM555CMLM709CHLM709CNLM71oCHLM710CNLM715CHLM725CHLM733CHLM733CNLM741CHLM741CMLM747CHLM747CNLM748CNLM 3046C NLM 3054C NTO -5 $ 3.00TO -5 .90Mini -dip .75Dip 1.10TO -5 .95Dip 1.40TO -5 2.80TO -5 .90Mini-dip .90TO -5 1.20TO -5 5.00TO -5 1.40TO -5 1.70TO -5 2.50Mini -dip .90TO -5 .45Dip .45TO -5 .60Dip .75TO -5 4.30TO -5 5.00TO -5 1.50Dip 1.50TO -5 .45Mini -dip .44TO -5 1.90Dip .90Dip .40Dip .95Dip 1.50Phase Locked LoopsLM567CM Mini -dip 2.10IC Power RegulatorsLM335K: 5V, 600mALM336K: 12V, 500mALM337K: 15V, 45OmA2.402.902.90PulseGeneratorInterdesign 1101: 0.1 Hz -2MHz,0 -5V Output, var. width, line orbattery operation. $159.00.Reg2524V circulatinDynamic29.0049.0034.0049.0059.0099.0039.00149.0089.0069.0079.00139.0089.00ADC, 3 Digit BCD, Sect. Count,Low Cost 119.00MINIMUMSEND CHECK OR MONEY ORDER (NO. C.O.D.) TO: ORDER: $10.00P.O. Box 2208P, Culver City, CA. 90230512Shift1-24: $4.00 / 25 up: $3.90ShiftRegisters1402A1403A1404A1405A14061407150615072505K2512K2524V2525V2533V280728082814DCMM5055NMM5056HMM 5057 NMM5058NTMS3114JTMS3133NCRegisait ter9300SERIES9300PC $1.00$ 7.90 9301PC 1.206.00 9304PC 1.506.00 9306PC4.50 9308PC6.902.502.501.503.00 9311PC 2.503.00 9312PC 1.204.00 9314PC 1.305.50 9316PC 1.506.006.009309PC9310PC4.00 9318PC 2.305.50 9321PC 1.2010.90 9322PC 1.304.00 9324PC 2.005.50 9328PC 2.508.20 9334PC 2.955.00 9338PC 3.305.00 9340PC 5.005.00 9341PC 4.1010.90 9342PC 1.159.50 9360PC 13510.90 9366PC 1.75TWO PHASE MOS CLOCK DRIVERMH0026CN $5.50California residents add 6% sales tax.JANUARY 1975 101

TUBESRADIO & T.V. Tubes -36 cents each. Send for freeCatalog. Cornell, 4213 University, San Diego, Calif. 92105.RECEIVING & INDUSTRIAL TUBES, TRANSISTORS. AllBrands - Biggest Discounts. Technicians. Hobbyists.Experimenters - Request FREE Giant Catalog and SAVE!ZALYTRON, 469 Jericho Turnpike , Mineola, N.V. 11501.TUBES receiving, factory boxed, low prices, free price list.Transleteronic, Inc., 1306 40th Street, Brooklyn, N.Y.11218A, Telephone: 212- 633 -2800.TUBES "Oldies ", latest. Lists free. Steinmetz, 7519Maplewood, Hammond, Indiana 46324.1930.1962 Radio Programs. Reels, $1.00 Hour! Cassettes,$2.00 Hour!... Mammoth Catalog, $1.25. AM Treasures, PERSONALSBox 192F, Babylon, N.V. 11702.CASSETTE LABELSlain white cassette labe s. !co cassette cleaners. ya per mailer hot Nope plastic boa. famous brand cassettes " L iae new'' IO il? meni or fiberglass reelsna for oven reel and cassette discount catalog 49 10-99 100 1ascetic Labels (Multiples of 10) 02 .OIS .0ortica Cassette Cleaner .65 60 SS .50Paper Mailer Boxes .03 .025 .022 .02nscelte otch Cassette SCPOHE. Bus 2. get ONE FREE 2.72 2.55 2.11 2.390.1/2'' Fiberglass Reels. Used .50 .50 .00 .35O I/2" Melal. NAB Hole. Used LOO 1.00 .90 .00Ius Postage by 01,151 and Zone Mioidlul6 Oaks. $0.00ION,AXITONE TAPE SALES Ew`imlo 0.60% OFF LIST PRICE. McCord Electronics, Box276 -T, Sylvania, Ohio 43560. GOVERNMENT SURPLUSTAPE AND RECORDERSRENT 4 -Track open reel tapes -all major labels -3,000different - free brochure. Stereo -Parti, 55 St. James Drive,Santa Rosa, Ca. 95401.108TEKTRONIX 321APORTABLE ALL -TRANSISTORIZED3 ", 5MHz TRIGGERED SCOPESWITH 10:1 PROBE $450.00MINIATURE TRIM POTS5K, 10K, 25K, 50K, 100K,$.75 EA. 3/$2.00MULTI -TURN TRIM POTSSimilar to Bourns 3010 style 3/16" x Ya" x11/4" 50, 100, 500, 2000, 5000, 10,000ohms. $1.50 ea. 3/$4.00PRINTED CIRCUIT BOARD41/2 "x61 /2" single sided fiberglass board, 1/16" thick, unetched$,50 ea. 5/$2.20LIGHT ACTIVATED SCR's,TO -18 200V lA $1.75NIXIE TUBESSimilar to Raytheon 8650tubes, with socket & datasheet $2.25 3/$6.00FPA -711 - THESE PHOTO DIODEARRAYS ARE USED TO READSEVEN LEVEL TAPE 100 maSPACING $5.95TIS 73 N FET $ 502N4891 UJT $ 50ER900 TRIGGER DIODES 4/51 002N6027 PROG. UJT $75ITS 1233 DUAL FET $1.95VERIPAX PC BOARDThis board is a 1/16" singlesided paper epoxy board,41/2 "x61/2" (standard veripax),DRILLED and ETCHED whichwill hold up to 21 single 14 pinIC's or 8, 16 or LSI DIP IC's withbusses for power supply connections.Is also etched for 22pin connector $5.25FLV 100 VISIBLE LED 5 50ME -4 IR LED S 40MCD -2 OPTO -ISOL 5.90GREEN GAP OSL -16 LED S 60RED GAP OSL -3 LED S 4014 PIN DIP SOCKETS 5.4016 PIN DIP SOCKETS 5.5010 WATT ZENERS3.9, 4.7 OR 5.6 V5.75 EA4 WATT ZENERS3.9. 5.6, 6.8 OR 12 V. 5.30 EASilicon Power RectifiersPRY 1A 3A 12A 50A100 .06 .11 .30 .80I 200400600.07 .16 .35 1.15.09 .20 .50 1.40.11 .25 .70 1.80800 .15 .35 .90 2.201000 .20 .45 1.10 2.60REGULATED MODULARPOWER SUPPLIES+ -15VDC AT 100 ma, 115VACINPUT $19.955VDC AT 1A, 115VACINPUT $19.95I N 4148 14/$1.00Terms: FOB Cambridge Mass.Send check or Money Order. IncludePostage. Minimum Order $3.00GOVERNMENT Surplus. How and Where to Buy in YourArea. Send $2.00. Surplus 30177 -PE Headquarters Bldg.,Washington, D.C. 20014.MANUALS for Govt Surplus radios, test sets, scopes. List50 cents (coin). Books, 7218 Roanne Drive, Washington,D.C. 20021.TRANSISTOR SPECIALS2N256 PNP GE TO-32N404 PNP GE TO-5.504/$1.002N1137B PNP GE TO-32N1016A NPN Si TO-82$ .95$.1.952N3904 NPN SI TO -92 4 $1.00MPS3393 NPN Si TO-92 41$1.002N3906 PNP Si TO-92 4/$1.00MPS A13 NPN Si TO-92 3/$1.002N3767 NPN Si TO-66$ .702N2222 NPN Si TO-18 5/$1.002N3055 NPN Si TO-3 $1.002N5296 NPN Si TO-220 $ .502N6109 PNP Si TO-220$ .552N4898 PNP Si TO-66$ .60MJ2252 NPN Si TO-66$ .902N3638 PNP Si TO-5 5/$1.002N2218A NPN Si TO-5C7MOS (DIODE CLAMPED)74C 1074C 15774C 165CD 4001CD 4002CD 4009CD 4010CD 4011CD 4012CD 4013CD 4016CD 4019CD 4022CD 4023CD 4025CD 4027CD 403041$1.00CAPACITORS CD 40506V 30 OF TANT. 5/$120V 4.7UF TANT. 5/$1 MAN -1, RED OR YELLOW12V 1OUF ELECT. 5 /$1 LED READOUT ....52.5050V 1000F ELECT 5.40 MAN -3 READOUTS 51.7525V 30UF ELECT 4/$1.00 MAN -4 READOUTS 52.001103 1024 bit RAM $4.75NEC 6003 2048 bit RAM $9.501101 256 bit RAM $1.758225 64 bit -write RAM $2.758223-PROGRAMMABLEROM$4.75MM5203-2048 BIT ERASABLEPROM $23.95Conductive Elastometer lowprofile calculator keyboard. A21/4" x 31/4" X 1/2" flex key.195K -6 keyboard having U-9, .,+, -, x, +, =, K +C buttons withoff on switch. $6.00CT5005 -12 DIGIT CALCULA-TOR CHIP $7.95TTL IC SERIES74L00- .30 7476- .477400- .18 7480- .657401- .18 7483 -1.107402- .18 7485 -1,307403- .18 7486- .487404- .22 7489 -2.757.405- .22 7490- .757406- .37 7491 -1.307407- .37 7492- .757408- .24 7493- .757410- .18 7495- .997411- .30 7496- .957412- .45 8220 -1.507413- .75 74107- .507416- .37 74121- .607417- .37 74123 -1.007420- .18 74125 -1.407426- .30 74126 -1.407427- .33 74150 -1.157430- .18 74151- .957432- .30 74153 -1.107437- .44 74154 -1.657438- .37 74157 -1.257440- .21 74163 -1.607441 -1.05 74164 -2.057442 -1.00 74165 -2.057445 -1.10 74173 -1.807446 -L15 74177 -1.807447 -1.15 74181 -3.607448 -1.20 74192 -1.507450- .18 74193 -1.457472- .40 74195 -1.007473- .43 75324 -1.757474- .43 75491 -1.107475- .758038C IC VOLTAGE CON-TROLLED OSCILLATOR ....$4.9555$ 60$2.15$$.5055$ 60555$$1.20$1.25$1.35$2.25$ 55$1.3565$1.35Full Wave BridgesPRV 2A 6A 25A200 .95 1.25 4.00400 1.15 1.50 5.00600 1.35 1.75 6.005311 -CLOCK CHIP 6 DIGIT BCDHOLD COUNT, OUTPUTSTROBE $7.755314 -CLOCK CHIP 6 DIGIT HOLDCOUNT, OUTPUT STROBE 57.755316 -ALARM CLOCK CHIP . $8.502513- 64x7x5CHARACTER GEN $9.952516- 64x6x8 STATICCHARACTER GEN $9.95SANKEN AUDIO POWER AMPSSi 1010 Y 10 WATTS ...$ 6.40Si 1025 E 25 WATTS ...$17.95Si 1050 E 50 WATTS ...$24.95LINEAR CIRCUITSLM 309K 5V IA REGULATOR $1.65723 -40 +40V REGULATOR 5.58301/748 -Hi Per. Op. Amp 5.35LM 320 -5 or -15V REGULATOR ...$1.75LM 376 -V to 37V POS REG. 5 58741A or 741C OP. AMP. S 35709C OPER AMP 5.29340T -5, 12, 15 18, 24VPOS. REG. TO. 20 $1.75101 OPER. AMP., HI PERFORM S.75LM 308OPER. AMP., LOW POWER 51.05747 -DUAL 741 5.75536 -FET INPUT OPER. AMP. $2.60537 -PRECISION OP. AMP. $2.60LM 3900 -QUAD OP. AMP. 5.58LM 324 -QUAD 741 52.20560 -PHASE LOCK LOOP 52.60561 -PHASE LOCK LOOP 12.60565 -PHASE LOCK LOOP $2.60567 -TONE DECODER $2.95703 -RF-IF AMP 5.55LM 370 -AGC SQUELCH AMP $1.15555-2 ys - 2 HR. TIMER 5 981458 DUAL OP. AMP. S 601456 OPER. AMP. 5.95LM 380-2W AUDIO AMP 51.45LM 377 -2W STERO AUDIO AMP. .. 52.60LM 381- STEREO PREAMP $1.75LM 382 -DUAL AUDIO PREAMP 51.75LM 311 -HI PER. COMPARATOR 5 95LM 319 -DUAL HI SPEED COMP. .51.25LM 339 -QUAD COMPARATOR $1.65TRIACSSCR'S- 1A 10 59 15 6A 35A1 a 11¡!lcTt111w,] ISend 20c for our catalog featuring Transistors and Rectifie s; 145 HAMPSHIRE ST. Cambridge, Mass.SOLID STATE SALESA 1 I1MRblilixi11.1 1 IiRT7iTT11liG>ri11 1 1 .600 1.70 2.30 3.00 3.00WE SHIP OVER 95%OF OUR ORDERS THEP.O. BOX 74ADAY WE RECEIVE THEMSOMERVILLE, MASS. 02143 TEL. (617) 547 -4005CIRCLE NO. 33 ON READER SERVICE CARDMAKE FRIENDS WORLDWIDE through internationalcorrespondence. Illustrated brochure free. Hermes, Berlin11, Box 110660/ZD, Germany.INVENTIONS WANTEDCASH -ROYALTIES for patented, unpatented inventions.Global Marketing Service, 2354 -P Telegraph, Oakland,California 94612.INVENTORS: Protect your ideas! Free "RecommendedProcedure ". Washington Inventors Service, 4227Washington Building, Washington, D.C. 20005.FREE PAMPHLET: "Tips on Safeguarding Your Invention."Write: United States Inventors Service Company, 708 -TCarry Building, Washington, D.C. 20005.FILE your own patent application. Complete informationand materials. Write: Inventor's Guide, 468 -R, GoodspeedRoad, Virginia Beach, Virginia 23451.I Name...Manufacturers NeedNew ProductsIf you have an idea for a new product, or a way tomake an old product better, contact us, "the ideapeople." We'll develop your idea, introduce it toIndustry, negotiate for cash sale or licensing.Send for our FREE "Invention Kit." It has aspecial "Invention Record Form," an importantbrochure, "Your Invention - Its Development, Protection& Marketing," and a Directory of 500Corporations Seeking New Products. You'll learnhow ideas become a reality!AddressCityRAYMOND LEE ORGANIZATION230 Park Avenue, New York, N.Y. 10017I'd like to find out how to take action on myidea. Send Free "Invention Kit No.A -112"Please Pr,ntStateSAN FRANCISCO LOSANGELES TORONTO VANCOUVER DENVER CHICAGOINSTRUCTIONZipIIIIILEARN ELECTRONIC ORGAN SERVICING at home allmakes including transistor. Experimental kit- troubleshooting.Accredited NHSC, Free Booklet. NILES BRYANTSCHOOL, 3631 Stockton, Dept. 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Cook's Institute, Dept. 13, Box 20345,Jackson, Miss. 39209.LOGIC MICRO/MINI-COMPUTER NEWSLOGICNEWSLETTER ©SAMPLE COPY $ I .00LOGIC NEWSLETTERPOB 252WALDWICK, N.J. 07463POPULAR ELECTRONICSAltaj Electronic BargainsPRICES SLASHED! WE WANT YOUR BUSINESS. SATISFACTION GUARANTEED ON EVERY ITEMMM5314 NATIONAL CLOCK CHIPThe most popular clock chip around. Wemade a huge special purchase of factoryfresh, prime units. Lowest price in USA.24 Pin DIP. 4 or 6 Digits. With Specs.$3.94 EACH [3 For $10)DIGITAL ALARM CLOCK ICThe newest and easiest to use alarm chipon the market today. Features:1. Single supply voltage.2. LED Intensity control3. Simple time set.4. 4 or 6 Digit LED Display5. AM -PM Indication6. 24 Hr. Alarm.7. 10 minute snooze.8. Outperforms MM5316Order #70250 - $6.95 (2 FOR $12)CT7001 BY CAL -TEXDigital alarm clock chip with calenderfeature. 4 or 6 digits. Also has timingcircuitry for radio ON -OFF control factoryfresh.$8.95JUMBO LED READOUTTwice the size of regular readouts. .65inches. Like Litronix DL747. Outperformsand easier to read than SLA -3, only 20MA per segment. Our best readout fordigital clocks.$2.95 ea (6 FOR $15) Common AnodeOPCOA SLA -1 LED READOUT.33 In. character. Left decimal pt. Uses7447 driver. Easier to read than MAN -1.Factory prime units. Best Price in USA!$.95 ea.CALCULATOR CHIP BONANZAPRICES SLASHED!The newest and easiest to use chipsavailable today. Made by famous US mfg.All are 28 pin DIP. Features: direct LEDsegment drive, low power consumption,internal keyboard debounce, internalclock oscillator, single supply voltage,internal keyboard encoding, and floatingdecimal point. Does not require manyexternal componentsants as do older typeslike CT5001 , 5002, 5005, etc. We offer themost sophisticatedfunctions for thelowest price anywhere.Chip #1 - 8 Digit, Constant, Six Function(+, -, x, +, %,-,p) - $5.95Chip #2 - 8 Digit, Memory, Six Function(+, - x, +,V,'1'') - $7.95Chip #3 - 8 Digit, Memory, Six Function( +, -, x, +, %, 11x) - $6.953 DIGIT LED READOUT ARRAYLike Litronix DL -33. 3 MAN -3 style readoutsin one package. Factory new units.Designed for calculators. Special -$1.19 (3 Digits)PRIME TTL DIP IC'S7400-164 7440-164 7492 -854 74165 -1.507402-164 7442 -694 7493 -854 74174 -1.757404 -161E 7445 -694 741 21-384 74175 -1.4974O6-24á 7447 -854 74123 -664 74181-2.757408 -16 7448-854 741 50 -69C 74192 -1.25741 0-1 64 7473-394 74151 -6 94 74193 -1.257413 -494 7474-38C 74153-954 7419 5-9547420 -164 7475 -694 74154-951V 74197 -1 .25'7430 -16 7476 -424 74157 -1.197437-39 7483 -794 74161 -L157438-394 7490-75$ 74164 -1.29JANUARY 1975RCA STYLE C-MOSCD4001-39¢ CD4012-44¢CD4002-39t CD4013-89¢CD4009-75t C D4017-1 .95C D4011-394LM309KTO -3 Case, 1 AMP 5 VDCVoltage Regulator. Brand NewBy National 95$7805 STYLE REGULATORSTO -220 Plastic Case 5VDC Regulator.Brand New by National - 89¢GE POWERTRANSISTOR ASSORTMENTPlastic power devices. Includes NPN andPNP, darlingtons, high voltage, highcurrent, and various other types. Casesare color coded for easy sorting. Untestedbut includes many useable units.SPECIAL - 20 FOR $1TTL IC ASSORTMENTVarious types. Most are marked. Our bestselling assortment. Untestedcludes many useable devices.but in-200 PCS FOR $3.95TIP -3055 BY TIPlastic version of 2N3055. NPN Silicon.8941 AMP SILICON RECTIFIERSIN4002 - 100 PIV - 84IN4007 - 1000 PIV - 174ZENERSIN746 - 400MW - 3.3VIN752 - 400MW - 5.6VYOUR CHOICE8 FOR $1PLASTIC DRIVER TRANSISTORSFor clocks or calculators.2N3904 - NPN 2N3906 -PNPYOUR CHOICE6 FOR $1MAN -3 LED READOUTSBrand new, factory prime units. .12 in.character. Common cathode. Perfect forcalculators. 3 FOR $1 Best Price Anywhere!'.DIGITAL WRISTWATCH CRYSTALBrand new, mfg. by CTS -KNIGHT. 32.768KHZ. Standard, most popular type.Special $2.50 ea.NI -CAD BATTERY SPECIALTwo cell pack. 2.75 V. Capacity is 250 MAHours. Two of these packs make a greatsupply for TTL. 954 ea.CIRCLE NO. 3 ON READER SERVICE CARDMINI CORE MEMORY SPECIALMfg. by DATARAM. Stores 180 words of18 bits each. With sense amps andassociated drive circuits. A completememory system. We include 50 pages ofdata and schematics. Data only $2.50Brand New. Special $24.95CALCULATOR BASIC KIT WITH TI CHIPIncludes case with matching all functionkeyboard, and 9 digits of LED readoutsplus a Texas Instruments TMS 103 NCcalculator chip. (Same style chip as in TIDatamath calculator). All the basics forbuilding your own hand held calculator.Special - $11.95 Kit Quantity Limited.BURROUGHS PANAPLEX II12 DIGIT READOUT#BR13251 Neon 7 segment readout.Latest design for calculators, etc. Requires160 VDC. Right hand decimals.Brand new, factory fresh. We includemating socket FREE. Special - $5.95NOTE: With purchase of above readoutarray we offer motorola 2N5401 PNP HighVoltage driver transistor for 104 each.REGULATED DC POWER SUPPLYBrand new by wanlass. DC output 17 to30 V. Rated 60 WATTS out. Our testsshow these units will put out 12 VDC bychanging one resistor. #OEM 60 -3. Originalcost $57.50. In original factory boxes,with specs. Special $14.95FACTORY NEW LED'SJumbo Red-Like M V5024 8l$1Jumbo Green -Like MV5222 -5/$1Jumbo Yellow -5/$1Mini Red -Like MV50 -10/$1ELECTROLYTIC CAPACITOR SPECIAL220 MFD at 25 WVDC. AXIAL Leads byGI. Brand New 8 FOR $1MINIATURE SWITCHRocker style. Small size. SPDT. Perfectfor use on digital clocks.4 FOR $1Our lower prices and superior qualityhave made ALTAJ one of the fastestgrowing electronic suppliers in the USA.Put your trust in our unconditionalmoney back guarantee.ALTAJ ELECTRONICSP.O. BOX 38544DALLAS, TEXAS 75238TERMS: Check or money order. No COD.Add 10% Pstg. and Hdlg. Tex Res. add5%.109

383 Mohr, Der Oder-Spree-Canal und seine Bauten. 384Was seine Gründung betrifft, so bestand der Untergrundhier unter den oberen Sandschichten aus theils blauem Thon,mit sehr vielen und grofsen Steinen besetzt, theils, wie sichnachher erwies, aus zwischen den einzahlen Thonschiehten lagernden, nur wenig starken wasserführenden ScblufFschichten,Bei den Bohrungen konnte von diesen Schichten leider nichtsbemerkt werden, ebenso entzogen sich die im Thon lagerndenSteine der näheren Beachtung. Da auch der Thon anscheinendwenig fest war, wurde eine Einfassung des Betonbettes mitSpundwänden und demnächstige Betonirung unter Wasser inAussicht genommen und mit dem Einrammen der Spundwändevorgegangen. Hierbei ergaben sieh jedoch durch die vorhandenenSteine sowie durch die ganz verschiedenartige Festigteitdes SchlufFs recht bedeutende Hindernisse, und es kam oft vor,dafs nach Aufstauchen der Pfähle um diese ganze Kastenaufserhalb herumgeschlagen werden mufsten. Die ßammarbeitenerforderten fast doppelt so viel Zeit- und Geldaufwand als beider kurz vor dieser Schleuse begonnenen Schleuse bei GrofseTränke* Endlich nach langen Wochen waren die Eammarbeitenbeendet und es konnte mit dem Aushub der Schleusenbaugrubezwischen den Spundwänden begonnen werden. Der Rammboden(also etwa Oberkante Spundwand) lag auf Ord. + 32,40, esblieben also noch bis zur Betonsoble auszuheben etwa 5 m.Nachdem der Aushub bis auf 1,50 m unter Oberkante Spundwandvorgeschritten war, wur-IMP^^ — —.ati"".r.r^~'^^^]E^ den die Aussteifungennach beistehender Zeichnungeingebracht undzwar in je 4,95 m eineSteife. Diese Steifenwurden nach der Längsrichtung hin gegen einander nöch durcheingelegte Hölzer abgesteift und auch der Erddrucfc gegen diebeiden Querspundwände vor den Häuptern wurde durch diesenoch abgefangen. Aufserdem waren die Steifhölzer, wie ansder Zeichnung ersichtlich, durch Eisen verstärkt.Der Aushub der Schleusengrube wurde bei "WaBBeihaltungim Trocknen vorgenommen und das Erdmaterial durch Kipplowrysheransgeschaßt. Nachdem ziemlich die ganze Arbeitvollendet war, fand leider am 28. Januar 1888 in der Abendstundeein Gleiten der oberen Thonschicht auf der unteren ander linken Längsspundwand nahe dem Oberhaupte statt, und diehierdurch entstandene Bewegung war so stark, dafs die Spundwändetrotz ihrer Stärke von 20 cm in Höhe der Baugrubensohleförmlich abgeschnitten und nach innen gedrängt wurden.Die Steifen, die dadurch natürlich ihre Spannung verloren, fielenherunter und die gegenüberliegende Spundwand wurde ebenfallsin die Baugrube hineingedrückt. Die hierbei in die letzteregelangten Btdmassen betrugen etwa 200 ehm. Es blieb nunnur übrig j an den beiden liängsspundwänden die Erde bis zurTTnterkante Beton abzugraben, die Böschungen durch Bekreuzungmit starken Faschinenwürsten zu befestigen, die Drängewassernach dem Gelände unterhalb der Schleuse, woselbst eine Dampfpumpeaufgestellt war, abzuleiten, so die gleitende Schichttrocken zu legen und nunmehr die Betonirung im Trocknen,d.h. bei diesem gesenkten Wasiserspiegel, auf der festenSchluffschichtvorzunehmen, was auch ohne besondere Schwierigkeitenglückte. Die umgeknickten Spundwände wurden, soweit sie nichtabgeschert waren, in Höhe der Betonoberkante abgeschnitten,diejenigen Stellen aber, an denen ein Abscheren derselbenstattgefunden hatte, bis zu der vorgedachten Höhe behufs Einbringungdes Betons mit wagerecht gelegten Brettern gegendas dahinter liegende Erdreich abgegrenzt Es gelang, denBeton vollständig fest und ohne Quellen herzustellen; nur eineQuelle im Oberhaupt mufste nach aufsen durch die Spundwandabgeleitet werden, was auch ohne grofse Mühe geschehen konnte.Sobald der Beton gehörig abgebunden hatte, was nach etwaacht Tagen eingetreten war, wurde das Wasser nur noch bis30 cm unter Oberkante Beton gehalten und mit den Maurerarbeitenbegonnen. Die Stärke des Betonbettes, die dem Entwürfegemäfs auf 2 m in der Mitte, 1,50 m an den Spundwändenangenommen war, wurde, um tiefere Aushebungenmöglichst zu vermeiden, je nach dem Stande -der Aushubarbei'ten vor dem Zusammenbrechen der Spundwände entsprechendvermindert, und dies konnte um so sicherer geschehen, als, wieschon erwähnt, die Betonsohle durchweg in festem blauen Schlufflag. Die einzelnen Stärken sind aus den Querschnitten ersichtlich.Die Abgleichung des Betons in der Schleusenkammererfolgte durch eine in Cement gelegte Klinkerflachschicht, währendin den Häuptern und Thorkammem stärkere Uebermauerungenstattfanden.Ea dürfte nun zur Verdeutlichung der Zeichnungen wohlgenügen, nur noch einige Worte über die Gestaltung und Ausführungder Umläufe und kleineren Anlagen hinzuzufügen, umdann zur näheren Beschreibung der beweglichen Schleusentheileüberzugehen.Das Oberhaupt ist, wie die Abb. 7 bis 9 auf Blatt 57zeigen, unterwölbt und der dadurch unter demselben entstehendeHohlraum von 7,78 m Breite, 1,62 m Kämpfer- und 2,40 mScheitelhöhe zur Wassereinführung in die Kammer benutzt. Indie eigentliche Thorkammer ist vertieft ein hölzerner Rahmeneingesetzt und durch Schranbenbolzen mit dem Mauerwerk verankert,in welchem vier Klappschütze von den gewöhnlichenAbmessungen, wie solche in den Schleusenthoren angebrachtwerden {vgl. Stauanlage in der Spree bei Charlottenburg, Zeitschriftfür Bauwesen Jahrgang 1886), eingelassen sind. Durchdiese fällt nach Aufrichten des Klappthores das Wasser senkrechtin den Schacht, der mit hochkantigem Klinkerpflaster in Cementabgerollt ist, und tritt dann durch die vorbin beschriebeneBogenöänung in die Kammer.Im Unterhaupt dagegen sind überwölbte Umläufe angelegt,die eine Einströmnngsöffoung von 1,20 m Breite bei1,535 m Kämpferhöhe und Halbkreisbogen und eme AusstrÖraungsöffnungvon 3,20 m Breite bei derselben Höhe und Ueberwölbunghaben. Dieselben sind etwa in der Mitte durch eingelegteKlappschütze von 1,10 m lichter Breite und 1,50 mHöhe abgeschlossen und erweitem sich trompetenartig nach demUnterwasser zu hinter dieser Einschnürung, während der vorderselben befindliehe Theil die Anfangsbreite von 1,20 m beibehältund mit einem Ringgewölbe überdeckt ist. Abb. 8 und 13auf Blatt 57 zeigen im Grundrifs und Durchschnitt diese Anordnung.Um ohne Trockenlegung der Schleuse Ausbesserungenan den Klappschützen bezw. deren Bewegungsvorrichtungen vornehmenzu können, sind vor und hinter denselben Schächte zumEinsetzen von Nothschützen angelegt, während die Oeffnung Überden Klappschützen mit einem Einsteigeschacht versehen istAlle in der Schleusenmaner belegenen Schächte smd mitEisenplatten in Winkeleisenrubmen abgedeckt Die Anlage derDammbalkenfalze, Schiffehalter und der Haltekästen, sowie der

The Dual 1229Q. Why many musiclovers will settle for nothing less.Many serious music lovers are not satisfiedunless every component in their system i the veryfinest in its class, with cost secondary.The 1229Q,Dual's highest -priced multi -play turntable, is one ofthese "no compromise" components.The 1229Q is a ful I -sized turntable with atwelve -inch dynamically balanced platter thatweighs a full seven pounds. Its massive platter isdriven by Dual's powerful Continuous -Pole/synchronous motor.The 8 -3/4" tonearm is mounted in a truegyroscopic gimbal that centers and balances itwithin both axes of movement. All four tonearmpivots turn on identical low- friction bearingspermitting flawless tracking at as low as 0.25gram. And since a turntable of the 1229Q's calibreis used most frequently in the single -play mode,the tonearm is designed to track at precisely thecorrect angle in that mode. With the exclusiveMode Selector, tracking angle can be instantlyadjusted for correct tracking at mid stack in themulti -play mode.Low capacitance tonearm leads and ananti -skating system with separate calibrations forconical, elliptical and CD -4 styli, make the 1229Qcompatible with any stereo and four -channelcartridge available or likely to be available in theforeseeable future. Other features include acalibrated illuminated strobe with adjustableviewing angle, and cueing damped up as well asdown to prevent bounce.The 1229Q is too new for test reports to haveappeared, but reports on its immediatepredecessor, the Dual 1229, indicate why it wasthe largest selling quality turntable ever made.Stereo Review called its rumble measurements"among the best we have yet made on aturntable: High Fidelity said, "It takes one stepfurther the progressive improvements that havemade top Dual models among the most popularturntables in component systems for the betterpart of a decade, to judge by readers' letters:'Stereo & HiFi Times' noted, "I unhesitatinglyrecommend it to anyone looking for the bestpossible record playing equipment:' And PopularElectronics rated it "the equal of any combinationof record playing components known to us"Of course, not everyone can afford the1229Q's price: $259.95. But every Dual turntable,starting with the 1225 at $129.95, provides thesame high quality materials, co r,-fully finishedparts and meticulous quality control that have longearned Dual its reputation for reliability.Thus which Dual you select is not terriblyimportant.Your choice can be made in terms of thelevel of refinement you require. And if, like manymusic lovers, you require every refinement it ispossible to have in a multi -play turntable, chancesare you too will choose the Dual 1229Q.DualCIRCLE NO. 4 ON READER SERVICE CARDUnited Audio Products120 So. Columbus Ave., Mt. Vernon, N.Y. 10553Exclusive U.S. Distribution Agency for Dual