Wiretap preventing device of catv terminal device

Abstract

Abstract PURPOSE:To ensure a fair operation of a system, by providing an address data check bit part and performing a visual-aural control of a TV channel with an output signal defined as OK/NG. CONSTITUTION:At a terminal the received polling data is compared with an address set by itself through a comparator 4d. If the coincidence is obtained with this comparison, the data is fetched among the following down-data to be used for visual-aural permission/inhibition. In this case, an address part 6 delivers an address signal added with a check bit, and this signal is checked at a check bit checking part 7. Then a switch SW3 is turned on with OK. While the part 7 checks a redundant bit of address and detects NG if the part 6 is remodeled. Then the SW3 is turned off. Therefore a visual-aural inhibition mode is set to give no actuation to a PLL unit 3. Thus the pictures are disturbed and cannot be viewed.

Inventors

• 👤 Isao Nishibori
• 👤 西堀　勲
• 👤 Kunihiko Nagasawa
• 👤 長沢　邦彦

Bibliographic Details