Appendix XI— ELECTRICAL AND ELECTRONIC TERMS 



HERTZ.— The international unit of frequency. 

 One hertz, abbreviated Hz, is equivalent to 

 one cycle per second. 



HETERODYNE.— The production of a difference 

 frequency (beat) by combining two frequen- 

 cies. The beat frequency, being lower than 

 the original frequency, is more readily 

 amplified. 



INTERMEDIATE FREQUENCY. -The fixed fre- 

 quency to which all RF carrier waves are 

 converted in a superheterodyne receiver. 



KILOHERTZ. —One thousand hertz and abbrevi- 

 ated kHz . 



OUTPUT.— The energy delivered by a device or 

 circuit such as a radio receiver or trans- 

 mitter. 



POSITIVE CHARGE.— The electrical charge 

 carried by a body which has become de- 

 ficient in electrons. 



POWER.— The rate of doing work or the rate 

 of expending energy. The unit of electrical 

 power is the watt. 



PROTON.— A positively charged particle in the 

 nucleus of an atom. 



PULSATING CURRENT. -A direct current, 

 which periodically increases and decreases 

 in value. 



LOUDSPEAKER.— A device that converts AF 

 electrical energy to sound energy. 



MICRO.— A prefix meaning one -millionth. 



MILLI.— A prefix meaning one -thousandth. 



MEGAHERTZ.— One million cycles per second 

 and abbreviated MHz. 



MICROPHONE.— A device for converting sound 

 energy into AF electrical energy. 



MODULATION.— The process of varying the am- 

 plitude (amplitude modulation), the frequency 

 (frequency modulation), or the phase (phase 

 modulation) of a carrier wave in accordance 

 with other signals in order to convey intel- 

 ligence. The modulating signal may be an 

 audiofrequency signal, video signal, or elec- 

 trical pulses or tones to operate relays, 

 etc. 



NEGATIVE CHARGE. -The electrical charge 

 carried by a body which has an excess of 

 electrons. 



NEUTRON.— A particle having the weight of a 

 proton but carrying no electric charge. It 

 is located in the nucleus of an atom. 



NUCLEUS.— The central part of an atom that 

 comprises protons and neutrons. It is the 

 the part of the atom that has the most 

 mass. 



OHM.— The unit of electrical resistance. 



OPEN CIRCUIT.-A circuit that does not provide 

 a complete path for the flow of current. 



OSCILLOSCOPE. -An instrument for showing 

 visually graphical representations of the 

 waveforms encountered in an electrical cir- 

 cuit. 



RADIATE.— To send out energy into space, as 

 RF waves. 



RADIO.— The science of communications in 

 which RF waves are used to carry intel- 

 ligence through space. 



RADIOFREQUENCY.— Any frequency of elec- 

 trical energy capable of propagation into 

 space. Frequencies normally are much 

 higher than those associated with sound 

 waves. 



RECTIFIERS.— Devices used to change alter- 

 nating current to unindirectional current. 

 These maybe vacuum tubes, semi-conductors 

 such as germanium and silicon, dry-disk 

 rectifiers such as selenium and copper- 

 oxide, and certain other types of crystal. 



SHORT WAVE.— Refers to radio operation on 

 frequencies higher than those normally used 

 for commercial broadcasting. The range of 

 frequencies extend from 1 500 kc to 30,000 kc. 



SUPERHETERODYNE RECEPTION. -A method 

 of receiving radio waves in which the process 

 of heterodyne reception is used to convert 

 the voltage of the received wave into a volt- 

 age of an intermediate frequency. 



TRANSCEIVER.— A combination of radio trans- 

 mitting and receiving equipment in a single 

 housing. 



TRANSMISSION LINE.— Any conductor or sys- 

 tem of conductors used to carry electrical 

 energy from its source to a load. 



TRANSMITTER.— Equipment used for gener- 

 ating and amplifying a radiofrequency signal 

 and radiating modulated radiofrequency car- 

 rier into space as waves. 



443 



