Television scrambling system
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United States of America Patent
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-
Jun 15, 1999
Grant Date -
N/A
app pub date -
Apr 9, 1996
filing date -
Apr 9, 1996
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A sync suppression, phase inversion scrambling system for a television signal is modified to improve its anti-piracy attributes SAW filters are switched during horizontal intervals to introduce scrambling The switching is a function of a mode signal and framing code signals of two different widths A false framing code signal is inserted during the vertical interval to switch the filters. Additional false framing code signals of sufficient width to embrace the vertical broad pulses in the television signal are supplied to impart amplitude changes to the vertical broad pulses Authorized decoders can recognize the false framing code signals as legitimate and follow the filter switching performed at the encoder (to restore the vertical broad pulses), whereas pirate decoders cannot The result is a total loss of vertical sync in television receivers connected to the pirate decoders
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