A CA module is a decoding module (translator) for use in digital TV receivers with Common Interface input (CI or CI+), e.g. flat screen TV, DVB-T receivers for TV via own antenna, cable TV tuners (DVB-C) or satellite receivers (DVB-S).
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The CA module means that the card can be connected to the device and understood correctly by the receiver and thus decode the TV signal. It is therefore important to choose the right CA module for the encoding system which the TV company broadcasts. The new CI+ modules are used primarily for TVs with DVB-T2 tuner and HD channels.