Astra Digital Radio.
A proprietary digital radio transmission method via analogue subcarriers of digital TV satellites (SES Astra) with receivers on (stationary) ground stations.
ADSL
A technology enhancing traditional telephone lines by transmitting 640,000 BPS per second. It allows the viewing of films on a normal screen but with a mediocre image quality.
Analogue
The TV signal transmission system currently in use and that is continuously propagated and transmitted through the medium in the form of electromagnetic waves.
ANSI (American National Standard Institute)
The American National Standard Institute: it develops and publishes standards for the communications sector: It represents the USA within the ISO.
Apogee
The point in a satellite´s orbit that is farthest from the Earth.
Arpanet
Is the "mother of all networks", including the Internet. Its architecture was developed by the US Department of Defence during the 60´s and 70´s, right in the middle of the Cold War.
ASCII (American standard code for information interchange)
The computer code used for the exchange of text files.
ATM (Asynchronous Transfer Mode)
A technique used to transfer any digital data (audio, still images, video, data, etc.) through fixed-size packets of bits.
ATTENUATION
A loss of signal. It is normally expressed in decibels, dB. Signal attenuation can occur in the cables connecting the antenna to the receiver or in the air space separating a transmitter from a receiver (attenuation per unit distance). Even rain can provoke signal attenuation.
AZIMUTH
A value expressed in degrees describing the angle of rotation of a parabolic antenna with respect to due North. For example, the South has an azimuth of 180° with respect to the North (0°).
