APPENDIX I GLOSSARY

AI-2 COMPARATOR—An equipment that compares incoming signals and selects the strongest to be fed to a teletypewriter through a patch panel. This is used in diversity operation. CONVERTER—An equipment that changes the audio output of a receiver to dc pulses. These pulses are fed to a tty to indicate marks and spaces. DETECTION—The separation of low-frequency (audio) intelligence from the high (radio) frequency carrier. DOUBLING UP—This is a type of two-equipment installation where one unit can be substituted for another in the event of failure. DOWN LINK—The frequency used to transmit an amplified signal from the satellite back to earth. DUMMY LOAD—A nonradiating device that absorbs the rf and has the impedance characteristics of the antenna. ECLIPSE—This occurs when the satellite is not in view or in direct line of sight with the sun. This happens when the earth is between them. ELECTROMAGNETIC INTERFERENCE—A term used to describe the degradation of a receiver or system. EPHEMERIS—A table showing the precalculated position of a satellite at any given time. EQUATORIAL ORBIT—An orbit that occurs when the plane of a satellite coincides with the plane of the earth at the equator. EXTREMELY HIGH FREQUENCY—The band of frequencies from 30 gigahertz to 300 gigahertz. EXTREMELY LOW FREQUENCY—The band of frequencies up to 300 hertz. FACSIMILE—The method for transmitting and receiving still images. These images can be maps, photographs, and handwritten or printed text. FADING—The variations in signal strength at the antenna of a receiver. FIBER OPTICS—Conductors or optical waveguides that readily pass light. FIDELITY—The ability of a receiver to accurately reproduce, at its output, the signal at its input. FORWARD AGC—The type of agc that causes an amplifier to be driven towards saturation. FRAMING—The process of synchronizing a facsimile receiver to a transmitter. This allows proper picture reproduction. FREQUENCY-DIVISION MULTIPLEXING—Multiplexing that transmits and receives the full 360 degrees of each sine wave. FREQUENCY SYNTHESIS—A process that uses hetrodyning and frequency selection to produce a signal. FREQUENCY SYNTHESIZER—A frequency source of high accuracy. GANGED TUNING—The process used to tune two or more circuits with a single control.