Kabushiki Kaisha Toshiba

American Television and Communications Corporation

Toshiba Audio-video Engineering Co.

Tsutomu Uekusa

Akinori Masuko

Wataru Kuroiwa

Shouji Uehara

Masatoshi Tanaka

Robert M Rast

Jyoji Maeda

W Sherwood Campbell

Watru Kuroiwa

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

The system relates to a system for preventing unauthorized viewing of CATV etc. wherein each terminal is provided with a terminal own address generator and an auxiliary address generator. The center station allows outputs of respective address generators to be sent thereto in conformity with a time map to compare a signal sent back from the center state with the own address and the auxiliary address of the terminal of concern. The center station confirms that there is no overlap of addresses of respective terminals to provide a receiving signal permission if an abnormal condition is not found. Such an address overlap takes place at the time when the system is initially powered or when the pirater enters. Thus, when an overlap of addresses occurs, the address of the terminal concerned is changed. For such an address, an initial address is used as the own address, and an address based on the pseudo number is used as the address offset and the auxiliary address. Since the overlap when the system is initially powered is mainly due to the addresses attached at the time of fabrication at a factory, an address offset is added, thereby to cope with this overlap. In addition, since the overlap after the system has been powered is due to the enlargement or the invasion of the pirator, an address offset is changed or an address based on the pseudo number used to cope with such an overlap.

Anti-tapping 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

Funabashi, Japan

Tsutomu Uekusa