Zenith Electronics Corporation

David L Walker

Frederick H Auld, Jr

A TV signal decoder including a pair of flipflops, for receiving vertical sync signals identified by a single vertical blanking pulse in field No. 1 and a pair of pulses in field No. 2, includes a time delay circuit for operating the second flipflop only in response to the two pulse field. The outputs of the flipflop are coupled to a pair of AND gates and are supplied with decoding information that is serially translated under control of the appropriate field signal for decoding the television signal. A counter identifies the horizontal line number and is coupled to a PROM where the decoding information is stored for a specific scrambling system. The PROM may be replaced to enable operation with a different scrambling system.

Method and apparatus for unscrambling sync-suppressed television signals

A non-linear sync signal processor for deriving a sync-like signal from video information with suppressed sync signals includes a differentiating circuit for deriving pulse potentials from the leading and trailing edges of suppressed sync signals, a pair of comparators for generating signals corresponding to the pulse potentials and a pair of non-retriggerable monostable timers, one for creating a 6 microsecond first window in response to a leading edge and the other for creating a 58 microsecond second window in response to a trailing edge occurring in the first window. The second timer is enabled by operation of the first timer and the first timer is inhibited during operation of the second timer. Thus only sync-like signals having three characteristics of conventional sync signals are regenerated.

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Arlington Heights, IL, United States of America

David L Walker