Zenith Electronics Corporation

Frederick H Auld, Jr

Michael E Long

Caitlin B Bestler

Richard G Merrell

Larry K Moreland

David L Walker

Rueen-Guang Shyu

A cable television plant scrambling system incorporates video inversion with a pair of mode signals included in the vertical blanking interval of a scrambled television signal for identifying the proper mode for a video inverting/non-inverting amplifier at a subscriber station. An encoded mode control signal in the form of a byte of data is sent periodically with the scrambled television signal for selecting which of the mode signals is operative. In the receiver, the mode signals are applied to the inverting/non-inverting video amplifier and the encoded mode control signal is supplied to a microprocessor which is provided with a decoding algorithm from the cable head-end. The microprocessor decodes the mode control signal and tells the inverting amplifier which mode signal to look to for proper operation. A new decoding algorithm is periodically downloaded to subscriber stations on an out-of-band basis to enable the encoded mode control signal to be changed.

Enhanced security for a cable system

A dual in-band/out-of-band CATV receiver includes a coupler that couples input signals to a tuner and decoder for demodulation and recovery of in-band data and to an FSK receiver for recovery of out-of-band data. The recovered data outputs of the decoder and of the FSK receiver are coupled to a data switch that has a common output that is coupled to a tuner/decoder microprocessor. The tuner/decoder microprocessor in turn supplies information to a switch microprocessor for controlling operation of the data switch to couple either in-band or out-of-band data to the tuner/decoder microprocessor. The data switch defaults to the in-band data position whenever a channel change occurs.

Dual in-band/out-of-band CATV system

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 non-linear sync signal processor for deriving a sync-like signal from video information with suppressed sync signals includes a differentiating circuit for deriving pulse potentials from the leading and trailing edges of suppressed sync signals, a pair of comparators for generating signals corresponding to the pulse potentials and a pair of non-retriggerable monostable timers, one for creating a 6 microsecond first window in response to a leading edge and the other for creating a 58 microsecond second window in response to a trailing edge occurring in the first window. The second timer is enabled by operation of the first timer and the first timer is inhibited during operation of the second timer. Thus only sync-like signals having three characteristics of conventional sync signals are regenerated.

Growing community of inventors

Barrington, IL, United States of America

Frederick H Auld, Jr