Demodulation of encrypted channels
The use of encryption systems is widely spread in digital pay television. the operator encodes the signals and the subscriber holds a Smart Card Giving access to those channels. The main limitation with this kind of solution is that each receiver specialises in a specific encryption system and can not be used for another system.
There is one alternative known as “Common Interface” which allows the use of standard receivers. In this case the receiver has a slot to insert various coditional access modules (CAM) and their corresponding Smart Cards. This lets the user access the digital television content of various providers, even if they use different encryption systems.