The Online World resources handbook

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Getting started http://home.eunet.no/~presno/bok/v2.html ?? 112 Kbits/sec Boca Research Inc. was the first to announce such a modem (November 1997). :KHQ \RX FRQVLGHU EX\LQJ D PRGHP ZLWK KLJKHU VSHHG UHPHPEHU WKDW JRLQJ IURP ESV WR LV D SHUFHQW LQFUHDVH ZKLOH JRLQJ IURP WR ESV JLYHV percent! If you now have 9600 bits/s, going to 28.800 will potentially triple the speed. MNP error correction and compression The Microcom Networking Protocol (MNP) is a U.S. industry standard for modem to modem communication with automatic error correction and compression. Automatic error correction is useful when there is noise on the telephone line. MNP splits the stream of data up into blocks before transmission. They are checked by the other modem upon receipt. If the contents are correct, an acknowledging message is sent back to the sending modem. If there is an error in the transmission, the sending modem is asked to retransmit. When using compression, files are being preprocessed before transmission to decrease their size. The result is that the modem has to send fewer bytes, and the effect is higher speed. MNP Level 3 and up send data between two modems synchronously rather than asynchronously. Since sending a start and stop bit with each transferred byte is no longer required, the effect is higher speed. MNP 4 or higher have automatic adjustment of block length when there is noise on the line. If the line is good, longer blocks are sent. The block size is decreased if the line is bad causing many retransmissions. MNP 5 has data compression. This gives a further increase in transfer speed by from 10 to 80 percent depending on the type of data sent. MNP 7 is capable of a three to one compression ratio. Both users must have their modems set for MNP to use it. The speed of your computer's COMM port Installing a super fast modem does not guarantee an increase in the effective transfer speed. The serial port of your computer may be a limiting factor. Owners of older MS DOS computers often have UARTs (serial port processors) in the Intel 8250 or National 16450 series. With these in the computer, it is difficult to achieve speeds above 9600 bps without losing data. Take this into account when investing in a modem. MNP and efficiency I call the Internet daily. My personal computer is set to communicate with a 28.800 bps modem at 57.600 bps. The modem sends data to the telephone line at 28.800 bps, this modem's maximum line speed. Data is received by the remote computer's 28.800 bps modem at 28.800 bps, and probably forwarded to the Internet server at an unknown higher speed. Why these differences in speed? MNP level 5 compresses data in the modem before transfer, and gives error free transfer to and from the Internet server at higher speed than by using 28.800 bps all the way through. The compression effectiveness differs by the type of data. When sending text, the effective transfer speed may double. Speed will increase further if the text contains long sequences of similar characters. Text is typically compressed by up to 63 percent. This means that a 2400 bps modem using MNP 5 may get an effective speed of around the double when transferring such data. 4 of 9 23.11.2009 15:50
Getting started http://home.eunet.no/~presno/bok/v2.html File transfers using MNP and V.42bis Files are often compressed and stored in libraries before transfer. Online services do this because compressed files take less space on their hard disks. Also, it is easier for users to keep track of files sent in a library file. You rarely get speed advantages when transferring precompressed files using MNP or V.42bis. With some modems, you must turn MNP and V.42bis compression off before retrieval of compressed files. Dumb or intelligent modem? Some modems are operated with switches or buttons on a panel. They do not react to commands from your computer. We call them dumb. You must dial numbers manually, and press a key on the modem, when you hear the tone from a remote modem. Only when the modem is connected to the remote modem, can you ask your communications program to take over. We call those modems 'intelligent' that can react to commands from your computer. Most of them react to commands according to the Hayes standard. Buy intelligent, Hayes compatible modems even when other standards may seem better. Most of today's communication programs are designed to be used by such modems. Note: Buy modems that use the Hayes extended command set. When a communications program, like Windows built in Terminal, tells the modem to "dial a number" or "go on hook," then the Hayes compatible modem will do just that. When you click on Dialer and Login in the Trumpet Winsock program, it will dial your Internet access provider automatically. When you click on Dialer and Bye, it will ask the modem will disconnect from the remote modem. If you press ALT D in the communications program Telix followed by the number "2," then it will locate the number to an online service in your telephone directory, and dial that number. When the connection with the remote modem has been set up, your modem will report back to you with a message like CONNECT 14400. This tells that a connection has been set up at 14400 bps. If I select "k" from a menu provided by my communications program's command scripts, then my system will retrieve today's business news from Tokyo and put them up on my screen. In the process, my system tells the modem to do several things, including "call a number," "speed 28800 bps," "redial if busy," "go on hook when done." The only thing that I have to do, is press "k". The communications program and the modem will do the rest. Automatic communication is impossible without an intelligent modem. The Hayes standard The U.S. company Hayes Microcomputer Products, Inc. pioneered command driven modems. Their Smartmodem became a success, and "Hayes compatibility" a standard for intelligent modems. Today, it is as unimportant to buy a Hayes modem to get access to Hayes commands, as to buy an IBM PC to run PC software. Automatic dialing (autodial) was one of Smartmodem's important features. The modem could call a number and prepare for data communication, once a connection had been set up. If the line was busy, it could wait a while and then redial. The operator could work with other things while waiting for the equipment to be ready for communication. The modem had automatic answer (autoanswer), that is, when someone called in, 5 of 9 23.11.2009 15:50
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Contents of The Online World resour
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The Online World resources handbook
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Will going online make me rich? htt
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The Online World: What is it? http:
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Using online services http://home.e
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Hobby, games and fun http://home.eu
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Home, education and work http://hom
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Your personal HealthNet http://home
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Electronic mail, telex, and fax htt
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Free expert assistance http://home.
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Your electronic daily news http://h
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Finding a needle in a bottle of hay
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Finding a needle ... (Part II) http
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Getting an edge over your competito
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Business: Locating country specific
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PART 3: WORKING SMARTER http://home
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Practical tips http://home.eunet.no
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Page 195 and 196: Gazing into the future http://home.
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Services offering access to the Int
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