A selective viewing control system for controlling viewing access to designated channels in a CATV system. A CATV control center sends to viewing control units a digital signal indicating which channels are to be jammed. In response, the viewing control unit produces a jamming signal, added with the...http://www.google.com.tw/patents/US4792971?utm_source=gb-gplus-share專利 US4792971 - Selective viewing control system for CATV
