The Illustrated Dictionary of Electronics - Loscha

intermittent commercial and amateur service • international farad 375periods, as in amateur (hobbyist) activity or infrequentcommercial service. ICAS ratings arehigher than continuous commercial service (CCS)ratings. Compare CONTINUOUS COMMERCIALSERVICE.intermittent condition A defect in a circuit or devicethat causes erratic and unreliable operation.The cause of such a problem is often difficult todetermine.intermittent dc See INTERMITTENT DIRECTCURRENT.intermittent direct current A regularly pulsedunidirectional current. Also called PULSATINGDIRECT CURRENT.intermittent duty A DUTY CYCLE of less than100 percent, but greater than zero. Generally, anoperating duty cycle of 25 to 50 percent.intermittent-duty rating The dissipation orpower rating of a component, circuit, or system,under conditions of intermittent use, usually a25-percent to 50-percent DUTY CYCLE.intermittent operation Operation characterizedby often long nonoperating intervals. Intermittentoperation is often random, whereas on-off operationtends to be regular.intermittent signal An interrupted signal resultingfrom the intermittent operation of a circuit ordevice.intermodulation Abbreviation, IM. 1. The (usuallyundesired) modulation of one signal by another,caused by nonlinear processing of the signals. 2.The heterodyning of components in the sidebandsproduced by an amplitude-modulated (AM)or single-sideband (SSB) transmitter.intermodulation distortion Abbreviation, IMD. 1.Distortion products in the output of an amplitude-modulated(AM) or single-sideband (SSB)transmitter, caused by heterodyning of componentsin the sidebands. 2. Distortion products inthe output of an audio amplifier, caused by heterodyningof the fundamental components. 3.The extent to which distortion as defined in 1occurs. See INTERMODULATION-DISTORTIONPERCENTAGE.intermodulation-distortion meter See INTER-MODULATION METER.intermodulation-distortion percentage Abbreviation,IDP. The degree to which a low-frequencytest signal modulates a higher-frequency test signalwhen both are applied simultaneously (in aprescribed amplitude ratio) to a device under test;IDP = 100(b – a)/a, where a is the peak-to-peakamplitude of the unmodulated high-frequencywave and b is the peak-to-peak amplitude of themodulated high-frequency wave.intermodulation meter An instrument for measuringpercentage of intermodulation distortion(IMD). The instrument combines a dual-frequencysignal generator, filter circuits, and percent-ofmodulationmeter. Also see INTERMODULATION-DISTORTION PERCENTAGE.intermodulation noise Electrical noise producedin one channel by signals in another; it is causedby INTERMODULATION.internal absorptance The ratio of flux absorbed ina substance to the flux leaving at the entry surfaceof the substance. It does not include energyreflected at the entry surface.internal amplification In a radioactivity countertube, current enhancement resulting from cumulativeionization initiated by an ionizing particle.internal arithmetic In a digital computer, arithmeticoperations performed in the computer, asopposed to those performed by peripherals.internal impedance The impedance in a device, asopposed to that added from the outside. CompareINTERNAL RESISTANCE.internal input impedance The impedance in a circuitor device, as “seen” from the input terminals.Compare INTERNAL OUTPUT IMPEDANCE.internal input resistance The resistance in a circuitor device, as “seen” from the input terminals.Compare INTERNAL OUTPUT RESISTANCE.internal noise Electrical noise generated within acircuit, as opposed to that picked up from outside.Such noise comes from transistors, diodes,integrated circuits, resistors, and any other componentthrough which current flows.internal output impedance The impedance in acircuit or device, as “seen” from the output terminals.Compare INTERNAL INPUT IMPEDANCE.internal output resistance The resistance in a circuitor device, as “seen” from the output terminals.Compare INTERNAL INPUT RESISTANCE.internal resistance 1. The resistance of a device,as opposed to added resistance. See, for example,METER RESISTANCE. 2. In a cell or battery, theequivalent resistance, resulting from imperfectconductivity of the electrolyte and electrodes,which limits the maximum deliverable current.internal thermal shutdown In an integrated circuit,the junction temperature at which thermalshutdown occurs. It is generally indicated in degreesCelsius (°C).internal transmittance The ratio of flux reachingthe exit surface of a material to the flux leavingthe entry surface. Reflection is not taken into account.The sum of internal transmittance and IN-TERNAL ABSORPTANCE is always equal to 1.international broadcast station A shortwavebroadcast station transmitting programs for internationalreception between 6 and 26.6 MHz.international callsign The call letters of a station,assigned within a country, according to themethod of arrangement (identifying letters, or lettersand numerals) prescribed by the InternationalTelecommunication Union.international candle See CANDLE.international coulomb A unit of electrical quantity,equal to 0.99985 absolute coulomb.international farad A unit of capacitance, equal to0.99952 absolute farad.