×

Addressable subscription television system having multiple scrambling modes

  • US 4,716,588 A
  • Filed: 10/29/1985
  • Issued: 12/29/1987
  • Est. Priority Date: 10/29/1985
  • Status: Expired due to Term
First Claim
Patent Images

1. A method for scrambling a video signal, said video signal including a plurality of sequential fields, each field having a plurality of active line portions preceded by a horizontal synchronization period comprising:

  • removing horizontal synchronization pulses from said synchronization period;

    compressing the amplitude of said active line portions;

    adding a pseudo synchronization pulse having an amplitude greater than said removed synchronization pulse to said synchronization period from which said horizontal synchronization pulses were removed, said pseudo synchronization pulse leading edge occurring at a time different than that of said removed synchronization pulse;

    changing the position of said pseudo synchronization pulses leading edge in subsequent fields; and

    ;

    adding an offset voltage to said video signal during the active line period of said video signal.

View all claims
  • 1 Assignment
Timeline View
Assignment View
    ×
    ×