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Pay television system with synchronization suppression

  • US 4,075,660 A
  • Filed: 07/23/1975
  • Issued: 02/21/1978
  • Est. Priority Date: 02/18/1972
  • Status: Expired due to Term
First Claim
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1. Encoding apparatus for a subscription television system, comprising, in combination, means for furnishing a television signal having a predetermined black level signifying picture black and having a plurality of vertical retrace intervals, each including a sequence of horizontal intervals separated by horizontal synchronization pulses, said horizontal synchronizing pulses having a predetermined synchronizing polarity relative to said black level;

  • pulse generator means for furnishing a sequence of substantially identical pulses;

    inserting means connected to said pulse generator means and said means for furnishing a television signal, for inserting a first, second and third one of said substantially identical pulses into, respectively, a first, second and third predetermined one of said horizontal intervals within each of said vertical retrace intervals at a polarity opposite to said synchronizing polarity and at a predetermined time instant following a first, second and third predetermined one of said horizontal synchronizing pulses, each immediately following the corresponding one of said first, second and third horizontal intervals, thereby creating an encoded television signal; and

    transmitter means for transmitting said encoded television signal to at least one receiver location.

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