Kabushiki Kaisha Toshiba

American Television and Communications Corporation

Toshiba Audio-video Engineering Co.

Shouji Uehara

Akinori Masuko

Wataru Kuroiwa

Tsutomu Uekusa

Masatoshi Tanaka

Robert M Rast

Jyoji Maeda

W Sherwood Campbell

Watru Kuroiwa

A system for level-compressing a sync signal component of a video intermediate frequency signal to scramble the signal. A compression pulse generation circuit generates a compression pulse in synchronism with a sync signal. A level compression circuit level compresses the sync signal component of the video intermediate frequency signal in response to the compression pulse. A sine wave generation circuit generates a sine wave having a frequency n times that of the sync signal in synchronism with the sync signal. A control data generation circuit generates control data for controlling a phase of the sine wave and generates a sine wave phase-controlled in accordance with the control data. A superposing circuit superposes the phase-controlled sine wave on an audio intermediate frequency signal and outputs a superposed signal. An output circuit outputs the level-compressed signal and the audio intermediate frequency signal. A detector detects the superposed signal and extracts the sine wave. A compression position detector detects a compression position and outputs a detection signal. An expansion pulse generation circuit generates an expansion pulse on the basis of the sine wave and the detection signal. A level expansion circuit expands the sync signal component in response to the expansion pulse.

Video signal scrambling system

A transmitter encoder has a gain selector for compressing the level of a horizontal sync signal component of a video intermediate frequency (IF) signal to scramble it, and an AM modulation degree controller for superposing a control signal, which indicates the timing for the level compression, on an FM audio IF signal in the form of AM modulation. The transmitter encoder further has an oscillator circuit for generating a sine wave with a horizontal frequency (fH) and an nfH sine wave having a frequency n times the horizontal frequency, and a mixer for mixing these sine waves to thereby provide the above control signal. A receiver decoder has an AM detector for detecting an AM component of the FM audio IF signal from the transmitter encoder to reproduce a composite signal and band filters for respectively extracting the fH and nfH sine waves from the reproduced composite signal. The receiver decoder further has a gain selector for expanding the compressed level of the horizontal sync signal component of the video IF signal from the transmitter encoder, by means of a sync expansion pulse generated on the basis of the fH sine wave.

Video signal scramble system

An external control unit for a CATV system has a CPU and a RAM with many kinds of memory maps. Reference data to be stored in the memory maps is transmitted from a central station. When a subscriber requests the tuning of a TV channel for a pay program to a converter tuner, the CPU in the external control unit can work, using the reference data.

Communication data processing device of cable television system

Growing community of inventors

Konosu, Japan

Shouji Uehara