Matsushita Electric Industrial Co., Ltd.

Satoshi Nakanami

Harumasa Kajita

Toshikazu Wakabayashi

Ichiro Kawashima

Tetsuo Kariya

Masami Tanaka

Toyokazu Yanagimichi

Noriyuki Kawamoto

In a pay television device, a horizontal sync signal, a vertical sync signal, and the like are removed from a composite video signal, and first-frequency and second-frequency signals for descrambling processing are attached in the intervals corresponding to the removed signals, thus eliminating the need for multiplexing signals which are necessary for descrambling processing on an audio signal.

Pay television

A key signal conversion device for use in a CATV television system in which more than one different scrambling process is performed, the conversion device receiving one of a scrambled high-frequency signal in a television system and a sound intermediate frequency signal in the television system, extracting a key signal for unscrambling the scrambling in the television system and adding the key signal to a nonscrambled television signal which is to be subsequently scrambled by a process other than a process used to scramble the received signal, the key signal conversion device including: a first detecting circuit, for receiving the one of a scrambled television signal and a sound intermediate frequency signal, and for detecting one of a synchronizing signal of the television signal and a synchronizing signal superimposed on the sound intermediate frequency signal; a gate circuit, for receiving the one of a scrambled television signal and a sound intermediate-frequency signal, and for extracting the key signal therefrom using the synchronizing signal detected by the first detecting circuit; a second detecting circuit, for receiving the nonscrambled television signal, and for detecting a synchronizing signal thereof; and an inserting circuit for superimposing the key signal on the nonscrambled television signal in a predetermined horizontal interval in the vertical blanking interval of the nonscrambled television signal by the gate circuit using the signal detected by the second detecting circuit.

Key signal conversion device for CATV system

A cable television system includes a transmitter and at least one receiver. In the transmitter, sync information is suppressed in amplitude to execute scrambling, and a sync width information signal and key data are superimposed on a television signal during a vertical blanking period. The sync width information signal has a burst form and a predetermined width, and represents whether sync information is present or absent. The key data represents contents of the scrambling. In the receiver, the sync width information signal is recovered, and a sync width information pulse corresponding to the sync width information signal is generated. A reference signal is generated on the basis of an edge of the sync width information pulse. The key data is extracted from the scrambled video information in response to the reference signal. Pseudo sync signals are generated in response to an edge of the sync width information pulse. The sync information of the scrambled video information is increased in amplitude in response to the extracted key data at timings determined by the pseudo sync signals.

Cable television system

Growing community of inventors

Kamakura, Japan

Satoshi Nakanami