Scientific-atlanta, Inc.

William P Lafay

Lamar E West, Jr

James O Farmer

Leo Montreuil

Joseph Graham Mobley

Leo J Thompson

Herman A Kruse

Frank R Little

Alex M Cook, Jr

Raheel Ahmed Khan

Anatoly Kozushin

Martin Taylor

Majid Ghanouni

Benny Hsu

Robert C Cheng

Christopher P Lewis

Lamar E West

The method, apparatus, and system for controlling audio anomalies by using a mute switch to prevent output of an auxiliary audio signal in a television signal with an auxiliary audio signal , such as a NICAM audio signal or dual language audio signal, adjacent to a first audio signal . The mute switch operation is a function of the type of receiver receiving television signal and a function of verifying the presence of an auxiliary audio signal in television signal . The present invention controls audio anomalies such as audio whistle and audio pop.

Method and apparatus for audio signal processing

An apparatus and method is provided for transmitting &ldquo;masked&rdquo; stereo audio signals in a signal distribution network such as a cable television system within the bandwidth constraints of conventional frequency allocation schemes. In various embodiments, left and right stereo audio signal components (L&plus;R and L&minus;R) are used to amplitude modulate a carrier using independent sideband (ISB) modulation without the transmission of a pilot signal. A jamming signal or low bandwidth data signal may be transmitted in place of the normal pilot tone. Various aspects of the invention contemplate the use of Hilbert transforms to perform the ISB modulation and demodulation.

Apparatus and method for masking audio signals in a signal distribution system

Networks which remove the jamming signal from the television signal supplied to subscribers for a premium T.V. channel in a cable (CATV) or other subscription television system utilizes surface accoustic wave (SAW) devices arranged to provide a broadband all pass response across the entire band covered by all of the transmitted television channels except for a notch at the frequency of the jamming signal. The narrow band response of the filter in the premium channel is such that the notch presents insertion loss at the jamming signal frequency and over a frequency range to accommodate shifts in the frequency response of the SAW devices with respect to the frequency of jamming signal, which insertion loss is about 100 times the insertion loss at the picture carrier frequency of the television signal, even though the picture carrier and the jamming signal frequency may be within about 200 KHz apart from each other. The network includes circuit elements which utilize the characteristics of the SAW devices to create a filter network which has a transmission null (notch) at the frequency of the jamming signal.

Television signal processing network for subscription television jamming

Scrambling and descrambling systems utilizing jamming signals provide improved pictures with minimal distortion due to ghosts and artifacts. The television signal is combined with a jamming signal or signals located preferably in the vestigial sideband (VSB) of the modulated picture carrier and at about a null in the spectrum of the modulation of the picture carrier by the horizontal sync. The jamming signal or signals also preferably are placed between the harmonic components of the horizontal sync which define the horizontal sync spectrum and at frequencies which comply with governmental regulations respecting frequency locations of strong signals of CATV purposes. The jamming signals are generated by phase locking to the horizontal sync signals of the television signals or to a submultiple of the horizontal sync frequency. Artifacts are further reduced by preemphasis of the transmitted television signal in the sideband opposite to that in which the jamming signal or signals are located and spaced by an equal frequency increment from the location of the jamming signal energy. In order to extract the jamming signal, so as to descramble the television signal for reproduction in the subscriber's television receiver, a network including at least one surface acoustic wave (SAW) resonator device is embedded in an all-pass network which allows essentially lossless transmission of the television signal spectrum, except for the jamming signal energy and enables that energy to be located close to (e.g., approximately 228 KHz) from the picture carrier in the VSB for enhanced security.

Jamming signal scrambling and descrambling systems for CATV

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Snellville, GA, United States of America

William P Lafay