General Instrument Corporation

Jerrold Electronics Corporation

Other

Joseph B Glaab

David R Huber

Alfred W Stufflet

Michael F Jeffers

John Griffin

David Grubb

Donald R Horne

John M Jeffers

John T Griffin

Charles L Dages

S Wayne Mundy

Jacob Shekel

A receiver which receives a multichannel signal and which detects and outputs an unscrambled desired signal to a video display and speaker unit includes a first unit, a second unit and a controller. The first unit comprises a frequency agile tuner for receiving said multichannel signal and for outputting a selected CATV signal. The a second unit includes a unit means for receiving the selected CATV channel signal; a unit for detecting whether the selected CATV channel signal is scrambled; and a descrambler for descrambling a scrambled CATV channel signal and for outputting a descrambled CATV channel signal. The controller controls the output of the receiver such that a signal is output from the first unit to said video display and speaker unit when the selected CATV signal is unscrambled and a signal is output from the second unit to the video display and speaker unit only when a scrambled signal is detected. The content of the selected CATV channel signal controls the operation of the second unit.

Cable television setback decoder automatic control

The depth of modulation and the absolute RF carrier level of an amplitude-modulated video signal are automatically adjusted. For adjustment of the depth of modulation, a sync tip of the video signal is sampled, corrected and normalized to a reference level, e.g., a 50% video level. A reference pulse is inserted into the video signal, e.g., in a sync pulse or in linesand/orof the vertical blanking interval. The reference pulse is sampled and compared to the normalized sync tip pulse to determine an error. The error is converted to an adjustment signal for a charge pump which increases or decreases the depth of modulation accordingly. For adjustment of the absolute carrier level, the insertion of a reference pulse is not required. Instead, a reference value is stored in a memory and retrieved for comparison with the corrected sync tip pulse. An error term is computed and converted to an adjustment signal for a charge pump which increases or decreases the absolute carrier level accordingly. Several modulation circuits can share a common microprocessor controller.

Automatic modulation and RF carrier level control of sync suppressed television signals

Conventional decoding systems for scrambled audio-visual signals are improved by providing a dual-side local oscillator that functions as a high-side oscillator if the incoming RF signal is unscrambled and as a low-side oscillator if the incoming RF signal is scrambled. The result is that the unscrambled signal is reversed from an audio-over-video transmission configuration to an IF signal with a video-over-audio configuration, and a scrambled signal is maintained in a video-over-audio configuration, the video-over-audio configuration being the configuration required for proper reception and use of the signal by a television set. To function as both a high- and low-side oscillator, the dual-side oscillator has independent voltage control and does not follow the tracking filter associated with the tuner.

Video/audio scrambling with single conversion tuners

A setback decoder monitors the IF output from a cable-ready receiver and automatically provides a descrambled audio/video signal back to the receiver for output to the subscriber. When the receiver is tuned to a CATV channel which provides signals in a scrambled format, the decoder detects the scrambled signal, determines whether the subscriber is authorized to view the selected program, and descrambles the signal to provide a descrambled output signal to the receiver. The receiver detects the audio/visual output from the decoder and automatically outputs the audio/visual information to the subscriber.

The passive interdiction system for CATV scrambling provides a plurality of passive, preselected negative signal traps for securing specific CATV channels. Each trap cyclically attenuates the desired CATV channel thereby confusing the AGC (automatic gain control) circuit of the television monitor-receiver or video cassette recorder (VCR) by rapid cancellation and restoration of the picture carrier and main signal components. The passive interdiction system is comprised of a plurality of SAW (surface acoustic wave) resonators tuned to specific frequencies corresponding to the carrier frequencies of the channels to be secured and are alternately keyed on and off by a 10 to 20 Hz square wave. Authorization and control of the secured channels originates at the cable provider's headend and is transmitted contemporaneously with the CATV programming. The authorization data is specifically addressed and decoded at unique interdiction units disposed within the CATV system. The SAW resonators exhibit a low value temperature coefficient yielding stable trap frequency responses.

Passive interdiction system for scrambling

The depth of modulation and the absolute RF carrier level of an amplitude-modulated video signal are automatically adjusted. For adjustment of the depth of modulation, a sync tip of the video signal is sampled, corrected and normalized to a reference level, e.g., a 50% video level. A reference pulse is inserted into the video signal, e.g., in a sync pulse or in lines,and/or,of the vertical blanking interval. The reference pulse is sampled and compared to the normalized sync tip pulse to determine an error. The error is converted to an adjustment signal for a charge pump which increases or decreases the depth of modulation accordingly. For adjustment of the absolute carrier level, the insertion of a reference pulse is not required. Instead, a reference value is stored in a memory and retrieved for comparison with the corrected sync tip pulse. An error term is computed and converted to an adjustment signal for a charge pump which increases or decreases the absolute carrier level accordingly. Several modulation circuits can share a common microprocessor controller.

Automatic modulation control of sync suppressed television signals

An information signal modulates a first optical carrier. The information signal is inverted to modulate a second optical carrier. The modulated first and second optical carriers are multiplexed into a single optical signal for communication over an optical fiber path. At a receiver, the optical signal is demultiplexed to recover the information signal and the inverted information signal. The recovered signals are combined to provide the information signal in the electrical domain with reduced distortion. A dual-detector balanced optical diode pair can be used to combine the recovered information and inverted information signals and provide an analog RF output. The apparatus is particularly suitable for the transmission of AM-VSB television signals.

Low distortion laser system for AM fiber optic communication

A block of amplitude modulated television channel signals frequency modulates an optical communication path. In one embodiment, the AM modulated channel signals FM modulate an RF subcarrier which, in turn, is used to intensity modulate an optical carrier for transmission. Frequency modulation of the RF subcarrier by the amplitude modulated channel signals is advantageously performed at microwave frequencies. The FM modulated subcarrier signal is then converted down to a frequency range compatible with transmitter and receiver components used in the system. The frequency modulation and conversion can be performed by a pair of voltage controlled oscillators coupled in a push-pull mode of operation. The outputs of the oscillators are combined in a double balanced mixer to down convert the FM signal spectrum. In another embodiment, the optical frequency of an optical carrier is FM modulated by the block of AM signals. Receivers for the FM modulated band of AM channel signals are also disclosed.

Method and apparatus for communicating amplitude modulated signals over

An improved external optical modulator provides reduced noise and distortion. An optical carrier to be modulated is split into a plurality of portions. A first portion of the carrier is modulated with an information signal. A second portion of the carrier is processed to provide an attenuating signal. The modulated carrier portion is combined with the attenuating signal to provide an attenuated optical carrier having improved apparent percentage modulation. In a preferred embodiment, the first carrier portion comprises a substantially greater amount of optical carrier power than the second carrier portion.

Fiber optic external modulator

An encrypted video distribution system includes a signal originating station which distributes television signals in a format unrecoverable by a standard television receiver. In particular, the normally occurring vertical and horizontal synchronizing pulses are deleted and, optionally also, video information is selectively inverted about a voltage reference potential intermediate the black and white levels. To permit synchronization restoration, a keying pulse is transmitted once each video field, and a synchronizing digital code burst transmitted once each frame--all at a fixed, predetermined intra-frame timed relationship. At each authorized subscriber location, the keying pulse and digital code burst are employed to lock a receiver frame clock which derivatively gives rise to all requisite reception-permitting synchronizing pulses. The transmitted information also contains information sufficient to restore the inverted video program content.

Video encryption system

Audio and control signals are digitized and inserted in the horizontal blanking intervals of the distributed composite television signal. The control signals are in the form of a data stream which includes a header containing group address, sync, and program-related information applicable to all receiving units, and a plurality of portions which are addressable to and contain information applicable to the control of particular individual receiving units in the addressed group. The information in the addressable portions can be altered on a real time basis such that the system operator has direct control over certain functions of individual receiving units from the transmission end.

Direct broadcast satellite signal transmission system

A television signal is scrambled by suppressing horizontal and vertical synchronizing signals while leaving unsuppressed a reference level during a selected reference interval. Descrambling of the received scrambled signal is achieved by comparing the unsuppressed reference level with the suppressed synchronizing signals and by adding a level representative of that comparison to the suppressed synchronizing signals, thereby to restore the latter to their proper levels.

Adaptive video descrambling system

A circuit for producing two carrier frequencies (e.g. video and audio) spaced by an accurately controlled, predetermined frequency includes a common reference oscillator connected in two phase-locked loops. Each of the phase-locked loops includes a voltage-controlled oscillator adapted to produce an output signal at one of the carrier frequencies, and a phase detector for comparing a different predetermined fraction of the outputs of the voltage-controlled oscillators in each of the loops with a predetermined fraction of the output frequency of the reference oscillator.

Growing community of inventors

New Hope, PA, United States of America

Joseph B Glaab