CEA-679-C Part A describes the physical and electrical parameters of the interface for conditional access (CA) devices for consumer electronics (CE). The purpose of this standard is to specify the interface to a CA device that performs the signal access and, optionally, descrambling and key generation. It is possible
to imagine that several CA devices could be interfaced to the same CE device, simultaneously (see
Annex A (informative)). This interface definition allows the entire CA system to be removable and hence
replaceable. Very few constraints, if any, are placed on the CA system architecture.