See Bit Error Rate.

Quadrature Amplitude Modulation. A method of combining two Amplitude Modulated (AM) signals - each having the same frequency, but differing in phase by 90 degrees, into a single channel, thereby doubling the effective bandwidth.

The length of the path between a communications satellite and an associated earth station.

Video-On-Demand. System that allows the viewer to see or choose a programme at the time the viewer specifies.

The method of channel sharing or utilisation of a single frequency or time slot by several locations.

ACM is a technology which can adjust the modulation and forward error correction or FEC of a link automatically to compensate the changes in link conditions (e.g. rain fade, level changes or interference). This technology is adopted in DVB-S2.

A device used to increase the strength of electrical signals.

A form of storing, processing or transmitting information through a continuous variable (rather than pulsed) signal.

The unit used for control and tracking the antenna pointing to the desired satellite

Device which picks up and delivers satellite signals to a receiver, most commonly a dish.