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Abstract

An decryption system which facilitates simultaneous decryption of multiple encrypted television channel signals thus making them simultaneously available for direct tuning in television receivers. The system is characterized by the utilization of a plurality of channel signals time synchronized with respect to a common timing reference signal. Each channel signal is encrypted in accordance with a predetermined encoding rule and distributed to subscriber sites where an unencrypted block of channel signals are made simultaneously available by decrypting them synchronously with the recovered timing reference signal in accordance with the inverse of the encoding rule. An interdiction apparatus then selectively jams a plurality of television channels from within the unencrypted block of channel signals thus making it possible for a provider to programmably interdict reception of selective channels by unauthorized subscribers. The invention can be advantageously used in both over-the-air and cable subscription television distribution systems to provide subscribers with a plurality of simultaneously available decrypted television signals and selectively encrypted channels, e. g., premium channels.

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First Claim