Pay tv scrambling by audio encryption

Abstract From the Canadian patent

Abstract of the Disclosure A subscription television distribution system provides a plurality of sources of television program channels each of which include a video signal and an encrypted audio signal with the encrypted audio signal including encrypted control and subscriber address data. There is a communication link connecting the plurality of sources with at least one receiving site such as a cable system head and which has means fox receiving the plurality of television channels. At the receiving site, the encrypted audio signals are separated from the television channel and are multiplexed together on an non-television channel carrier. An identifying tag is added to each of the video …