Glossary: C

CA module

Conditional Access module

A unit in the form of a plug-in card which is inserted in a special socket in the digibox to receive encrypted television channels. The CA module is connected to a standardised interface. The viewer can then insert their viewing.


Cable TV, cable television

Channel coding

The various techniques used for transmitting digital video, audio and data signals via a medium such as satellite, cable or terrestrial transmission.


A system pioneered by ASTRA that provides a unique form of in-orbit back-up. If there is a problem with a transponder, a back-up transponder on the same satellite, or a co-located satellite, is immediately activated. This system guarantees customers the best operational security and reliability in the industry.



The method of representing information (video, audio, data) with a series of discreet digital codes. Different from "conditional access".

Common interface connection

The interface for the plug-in computer card (PCMCIA) in the receiver designed to carry the conditional access subsystem.


In order to make more efficient use of transmission capacity, digital broadcast signals are reduced in size by digital compression. This has a minimum effect on the received signal quality but allows several compressed TV channels to be transmitted in the space required for one analogue channel.

Conditional access

A system that controls access to pay and copyright-protected services.

Coverage area

The geographical area covered by a satellite transponder. The area within which good quality reception can be guaranteed. Commonly known as the "footprint". A satellite may have transponders with different coverage areas and even have steerable "antenna beams" which can be aimed at different areas (this may vary during the life of the satellite). Outside the coverage area the signal declines rapidly and reception is normally not acceptable. Variations in signal strength occur here.


Cathode ray tube

A TV tube technology that converts electrical signals into a picture, based on a glass funnel-shaped vacuum tube. It is rapidly being replaced by flat-panel technologies.