Appendix I - Continued

AI-2 CONTROL-GRID MODULATOR—Uses a variation of grid bias to vary the instantaneous plate voltage and current. The modulating signal is applied to the control grid. CONVERSION—The process of changing ppm or pcm to pdm or pam to make them easier to demodulate. CRYSTAL MICROPHONE—Uses the piezo-electric effect of crystalline materials to generate a voltage from sound waves. CUSPS—Sharp phase reversals. CW DEMODULATOR—A circuit that detects the presence of rf oscillations and converts them into a useful form. CYCLE—360 degree rotation of a vector generating a sine wave. DEMODULATION—The removal of intelligence from a transmission medium. DEMODULATION or DETECTION—The process of re-creating original modulating- frequency intelligence from the rf carrier. DEMODULATOR or DETECTOR—A circuit in which demodulation or restoration of the original intelligence is achieved. DIODE DETECTOR—A simple type of crystal receiver. DUTY CYCLE—The ratio of working time to total time for intermittently operated devices. DYNAMIC MICROPHONE—A device in which sound waves move a coil of fine wire that is mounted on the back of a diaphragm and located in the magnetic field of a permanent magnet. EMITTER-INJECTION MODULATOR—The transistor equivalent of the cathode modulator. The gain is varied by changing the voltage on the emitter. FIDELITY—The ability to faithfully re-produce the input in the output. FINAL POWER AMPLIFIER (fpa)—The final stage of amplification in a transmitter. FIXED SPARK GAP—A device used to discharge the pulse-forming network. A trigger pulse ionizes the air between two contacts to initiate the discharge. FOSTER-SEELEY DISCRIMINATOR—A circuit that uses a double-tuned rf transformer to convert frequency variations in the received fm signal to amplitude variations. Also known as a phase-shift discriminator. FREQUENCY DEVIATION—The amount the frequency departs from the carrier frequency. FREQUENCY MODULATION (fm)—Angle modulation in which the modulating signal causes the carrier frequency to vary. The amplitude of the modulating signal determines how far the frequency changes and the frequency of the modulating signal determines how fast the frequency changes. FREQUENCY MULTIPLIERS—Special rf power amplifiers that multiply the input frequency.