Abstract: A subscription TV decoder for processing encoded audio and video signals in which the TV program audio information is received as an audio subcarrier includes means for decoding the video signal, a filter for separating the decoded video and audio signals, and a filter for separating the audio signal from the audio information subcarrier. The audio information subcarrier is multiplied to raise it to the frequency of the audio signal and is then recombined with the decoded video signal.

Abstract: A subscription TV decoder for processing encoded audio and video signals utilizes decoder enabling signals which are transmitted as audio subcarriers and have data and address portions thereof. The decoder includes audio and video decoder circuits and a decoder enabling circuit. The enabling circuit has address storage means and means for comparing the address portion of a received message with the stored address. There are means responsive to the address comparison means for storing the data portion of the message. The enabling message utilizes an address common to a plurality of subscribers and there are means responsive to a received enabling message for comparing the stored data with the enabling message data and to enable the audio and video decoder circuits in response to correspondence therebetween.

Abstract: A means for decoding a generally constant frequency sine wave scrambled television signal uses an automatic gain control circuit in a closed loop. The scrambling, applied at the head end of the television system, applies a greater scrambling level to the audio carrier than it does to the video carrier. The unscrambling signal, the detected audio carrier scrambling signal, is combined with the scrambled signal in an amplifier circuit, the output of which is a basic television signal. There is a residual of the scrambling sine wave remaining in the audio carrier output after unscrambling, but little or no residual scrambling remaining on the video carrier. The residual audio carrier scrambling signal is detected and amplified for application as the unscrambling signal.