A decoder for reconstructing a standard composite video signal with standard synchronizing pulses from a video signal V with only gray sync encoding E.sub.GS, of a repetition rate f.sub.GS, and comprising a first generator for generating a signal E.sub.VCO having a controllable frequency f.sub.VCO which,...http://www.google.com/patents/US4454544?utm_source=gb-gplus-sharePatent US4454544 - TV Privacy system using gray sync
