Importance

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Abstract

In order to provide higher efficiency of security in sync suppression scrambling of subscription TV signals, the signals are encoded with a timing pulse having a selected time delay relationship with the suppressed horizontal sync intervals of the TV signals. The timing can be implemented digitally by selecting a plurality (e.g., 12) of different timings. The timing can also be dynamically varied. The TV signals are descrambled by restoring the sync pulses at only those receiving stations authorized to receive the premium subscription programming which have circuits for generating restoring pulses with the selected time relationship upon reception of the timing signals. Accordingly, the use of unauthorized descramblers, which are insensitive to the timing signals or do not provide the restoring pulses in proper time relationship, is discouraged.

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First Claim