Television signal protection system - uses encoding tone signal with corresp. decoder at each authorised reception station

摘要

The television signal protection system prevents a transmitted television signal from being evaluated at unauthorised reception stations. At the transmitter only the tone signal of the television signal is encoded, with each of the licensed reception stations provided with a corresponding decoder. Pref. the coder for the tone signals is specially digitalised, each of the corresponding decoders having a similarly programmed D/A converter. A digital receiver identification signal may be superimposed on the digital tone signal. USE - For preventing access to transmitted programmes except by authorised user.