Image signal transmission method

Abstract

Abstract PURPOSE:To prevent wire tapping and furtive glance by a general subscriber, by making a CATV system have a privacy function so that an independent tariff system can be taken, in a picture signal transmission system. CONSTITUTION:When a subscriber's terminal B applies picture service to a program center A by operating a keyboard 14, a key code train of a secret number set in advance is transmitted to the subscriber's terminal B through a bi-directional circuit F. It is stored in a key code memory 13 in the terminal B. In this case, in a program center A, a key code signal for switching a channel is superposed on a picture signal from a picture file group 1 and is multiplexed, in an in-channel signal superposing device 2, and is sent to the terminal B through a CATV circuit D. In the terminal B, code information from the memory 13 is collated with an in-channel signal, a channel selector 11 is switched, and picture service is obtained, therefore, a subscriber's terminal which receives no key code train cannot discriminate contents of a program.

Inventors

• 👤 Hisanori Terajima
• 👤 久憲 寺嶋

Bibliographic Details