PRELIMINARY
B-1
Term
Meaning
A
Active Repeater
A re-radiation device associated with a transmitting/receiving antenna system that
re-directs and boosts the power of intercepted radio frequency energy. They may
also apply some processing to the signal as well.
Alarm Indication Signal
(AIS)
A signal that is transmitted in lieu of the normal signal in order to maintain
transmission continuity. It indicates to the receiving terminal that there is a
transmission fault located either upstream or at the transmitting terminal.
Alternate Mark Inversion
(AMI)
Digital transmission in which successive “1” signals are of opposite polarity.
American Wire Gauge
(AWG)
A system that specifies wire size. The gauge varies inversely with the wire
diameter.
Ampere
Unit of electrical current based on charge per second.
Amplitude
The magnitude of a waveform when measured from the mid-point to the peak of
the wave.
Analog
A signal in the form of a continuously varying quantity such as voltage, frequency
or phase.
Analog to Digital Converter
(ADC)
A device that takes an analog signal (e.g., voice) and digitizes it into data format.
Antenna
Device used to concentrate and direct the energy of a signal into a tight beam.
Parabolic or dish, grid, and Yagi are different varieties of antennas.
Antenna Gain
The ratio of the power radiated by an antenna in a specific direction versus the
power required to produce this same strength if an isotropic antenna were used.
Attenuation
The measure of the loss of power in a microwave signal as it travels between two
points. It is measured in dB.
Automatic Gain Control
(AGC)
Circuitry by which the gain of an amplifier is automatically controlled so that the
signal level is virtually constant for varying input signal levels.
APPENDIX B GLOSSARY OF TERMS
