Zenith Electronics Corporation

Oak Industries, Inc.

Richard G Merrell

Pieter Den Toonder

Graham S Stubbs

Caitlin B Bestler

Frederick H Auld, Jr

Gordon E Kelly

Johannes C Seltenrijch

Glenn P Doles

John A Lund

Mutsuo Nakanishi

Rueen-Guang Shyu

Fredreck H Auld

A cable television system includes a headend unit having a plurality of program signal sources, encoders, scrambling circuits, and channel modulators for producing a plurality of program channels modulated at a corresponding plurality of cable system carrier frequencies. An address computer within the headend unit is operative upon the encoders to provide the insertion of a message packet within the vertical blanking interval of the program signals. The scrambler circuits render the program signal unviewable by conventional television receivers. A cable system decoder is coupled to the headend by a cable and includes a conventional tuner, intermediate frequency amplifier and detector. A decoder processor is coupled to a channel selection input and to the tuner to provide channel selection in accordance with a user input. The decoder processor examines the message packet during the vertical blanking interval to determine authorization of the decoder to display the received program channel. A descrambler is coupled to the processor and the tuner IF and detector to descramble the program signal if authorization is detected. A modulator modulates the descrambled signal upon a fixed channel carrier for application to a conventional television receiver.

Cable television system having dynamic market code shuffling

A master and a slave counter have their outputs coupled to an exclusive OR gate which in turn, supplies the D input of a flip-flop. Clock pulses are coupled to the slave counter through an AND gate which is enabled by the Q output of the flip-flop. Clock pulses to the slave counter are inhibited upon occurrence of an output therefrom and until a succeeding output of the master counter occurs, at which time clock pulses are again supplied to both the slave counter and the master counter to synchronize the operation thereof.

Apparatus for synchronizing the operation of master and slave counters

A subscription television system includes a head-end for transmitting selected fields of a television signal in a scrambled form, the scrambled fields being identified by an encrypted mode control code inserted in a selected horizontal line of the preceding vertical interval. The mode control code is formed such that a predetermined non-transmitted control code is realized when the mode control code is processed with vertical interval system control data according to a selected function. A decoder processes the received mode control code and system control data according to the selected function to reconstitute the predetermined control code for enabling unscrambling of the following field. The decoder may employ majority voting techniques whereby not all of the bits of the reconstituted control code need be properly recovered to enable the unscrambling function.

Data encryption technique for subscription television system

An automatic homing system for a subscription television signal decoder comprises a tuning system responsive to a decoder off-command signal for operation in a search mode wherein successive television channels are sequentially tuned until a subscription television signal is detected. As a result, the memory circuits of the decoder may be refreshed with updated subscriber authorization data in response to a transmitted subscription television signal even though the decoder is turned off.

Automatic homing system for a subscription television signal decoder

A circuit for controlling the operation of a cable television alarm device in accordance with an alert signal and an all-clear signal developed by a subscriber decoder in response to broadcast codes received over the cable network comprises a flip-flop responsive to the alert and all-clear signals for activating and de-activating the alarm device respectively and a manually operable single-pole switch for controlling the operation of the flip-flop. The switch is displaceable between first and second switching positions for enabling and disabling the flip-flop and is momentarily displaceable to the second switching position for clearing the flip-flop.

Control circuit for CATV alert system

A cable television converter includes an oscillator and mixer for conversion of a selected input television channel to the specific output frequency of the converter. There is a program selection device, and a memory responsive thereto whereby a subscriber may designate certain channels for conversion to the output frequency. The program selection device provides for restricting access to only those designated channels in the memory whereby a subscriber may control access of members of the household to only certain permitted channels.

Catv converter with keylock to favorite channels

An audio and video signal coding system in which the normal sync pulses in the horizontal and vertical blanking intervals are suppressed, and clock and control data as well as digital audio data is inserted therein. The data, both audio information and clock data in the horizontal blanking interval is further distorted by the application of a periodic waveform and/or voltage level enhancement of certain portions of the horizontal blanking interval.

Method of coding audio and video signals

A converter/decoder for use in subscription television includes means for converting any input TV channel to a predetermined output channel. Decoding means are connected to the converter at its output for decoding the selected output channel. The decoder is enabled in response to data carried on the TV signal which describes the program level of the particular selected channel. The means for enabling the decoder includes a comparison circuit which compares the television signal program level data with authorization data and performs an enabling function when there is correspondence between the two data entries. The authorization data may be received by the converter/decoder simultaneously with the program level data, but at a frequency other than that of the television signal, for example, at a frequency in the FM band.

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Hebron, IL, United States of America

Richard G Merrell