APPENDIX XI 



ELECTRICAL AND ELECTRONIC TERMS 



ALTERNATING CURRENT (a-c). -Current in 

 which the change-flowperiodically reverses, 

 as opposed to direct current(d-c), and whose 

 average value is zero. 



AMPLIFIER.— A device used to increase the 

 signal voltage, current, or power, generally 

 composed of a vacuum tube and associated 

 circuit called a stage. It may contain 

 several stages in order to obtain a desired 

 gain. 



AMPLITUDE.— The maximum instantaneous 

 value of an alternating voltage or current, 

 measured in either the positive or negative 

 direction. 



ANTENNA.— A conductor or system of con- 

 ductors for radiating or receiving radio 

 waves. 



BATTERY.— Two or more primary or secondary 

 cells connected together electrically. The 

 term does not apply to a single cell. 



BLACK SIGNAL.— The signal at any point in a 

 facsimile system produced by the scanning 

 of a maximum density area of the chart copy. 



CARRIER FREQUENCY. -The frequency of an 

 unmodulated carrier wave. The RF com- 

 ponent of a transmitted wave upon which an 

 audio signal or other form of intelligence 

 can be impressed. 



CIRCUIT.— The complete path of an electric 

 current. 



CIRCUIT BREAKER.— An electromagnetic or 

 thermal device that opens a circuit when the 

 current in the circuit exceeds a predeter- 

 mined amount. 



COAXIAL CABLE.— A transmission line con- 

 sisting of one conductor, usually a small 

 copper tube or wire, within and insulated from 

 another conductor of large diameter. Radi- 

 ation from this type of line is practically 

 zero. 



CONDUCTOR.— Any material suitable for car- 

 rying electric current. 



CYCLE.— One complete positive and one com- 

 plete negative alternation of a current or 

 voltage. 



DIPOLE ANTENNA.— An antenna one-half wave- 

 length long. 



DIRECT CURRENT. -An electric current that 

 flows in one direction only. 



ELECTRON.— A negatively charged particle of 



matter. 

 ENERGY.— The ability or capacity to do work. 



FREQUENCY.— The number of complete cycles 

 per second existing in any form of wave 

 motion; such as the number of cycles per 

 second of an alternating current. 



FREQUENCY METER. -A meter calibrated to 

 measure frequency. 



FREQUENCY MODULATION. -The process of 

 varying the frequency of an RF carrier wave 

 in accordance with the amplitude and fre- 

 quency of an audio signal. The amplitude 

 of the modulated wave stays constant. 



FUSE.— A protective device inserted in series 

 with a circuit. It contains a metal that will 

 melt or break when current is increased 

 beyond a specific value for a definite period 

 of time. 



GAIN.— The ratio of the output power, voltage, 

 or current to the input power, voltage, or 

 current, respectively. 



GENERATOR.— A machine that converts me- 

 chanical energy into electrical energy. 



GROUND.— A metallic connection with the earth 

 to establish ground potential. Also, a common 

 return to a point of zero potential. The 

 chassis of a receiver or a transmitter is 

 sometimes the common return, and therefore 

 the "ground" of the unit. 



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