Common Interface is an International standard that the manufacturers of common interface modules (CAM) have agreed to respect. The following CAM's are officially compatible with TELE System receivers: Aston, Aston Crypt, Irdeto, Viaccess, Cryptoworks, AXAS, Magicmodule, FreeX, and ZetaCam.
Remember that there are also "multi-standard" CAM's that are dedicated only to developers. These modules are not official and their compatibility with the TELE System common interface decoders cannot be guaranteed. Therefore we highly recommend you only use original CAM's.