Abstract: A method and apparatus are provided for descrambling a sinewave scrambled television signal. The television signal is applied to a dual loop circuit that detects AM sinewave modulation on the television signal sound carrier. The detected modulation is applied to the picture carrier of the television signal in a first loop of the circuit to cancel the AM sinewave modulation therefrom. The detected modulation is applied to the sound carrier of the television signal in a second loop of the circuit to increase the AM sinewave modulation on the sound carrier within the loop. The net loop gain of the first loop is then lowered to minimize the application of noise from the sound carrier to the picture carrier.

Abstract: A television transmission system replaces the standard FM audio portion of a television signal with digital audio. Three digital audio channels are time division multiplexed on the sound carrier, using combined multi-phase and AM modulation. The audio signals are digitized using adaptive delta modulation techniques. Video vertical and horizontal framing, as well as the audio carrier phase reference, audio data bit time and frame reference, and various control data is carried using AM modulation. The digital audio information is carried using multi-phase modulation. The composite data stream may be serially encrypted to provide security and prevent unauthorized reproduction of the video and/or audio portions of the television signal.

Abstract: An apparatus and method are provided for receiving and reproducing stereo television sound. A transmitted television signal is received that contains a first component comprising the sum of first and second stereophonically related audio signals and a second component comprising the difference between the first and second stereophonically related audio signals. The first and second components are converted to produce a first sound carrier centered at a first intermediate frequency and a second sound carrier centered at a second intermediate frequency. The first component is detected from the first sound carrier at the first intermediate frequency. The second component is detected from the second sound carrier at the second intermediate frequency. The detected first and second components are combined to produce a left channel audio output and a right channel audio output.

Abstract: A cable television converter is retrofitted for use in reproducing stereophonic broadcast television sound. A composite signal is produced comprising the scrambled output signal from the converter tuner, the reception enable control signal from the converter's digital processor, and the output signal from the converter's remote control detection circuit. The composite signal is applied to a stereo adapter which separates the audio signal portion of the composite signal into left and right stereo signals, extracts the enable control signal from the composite signal, and outputs the left and right stereo signals for audio reproduction upon authorization indicated by the extracted enable control signal. Remote volume control and selection of a second audio program (SAP) is also provided.

Abstract: A timing signal generator for recovering timing signals in scrambled video signals in which the synchronizing signals are suppressed includes a tuned detector responsive to the color burst signal contained in the back porch of the suppressed horizontal blanking pulse. The vertical interval is detected as the absence of color burst for a specified time interval, and horizontal sync information is obtained by the detection of the first color burst after an absence of color burst.