In a jamming signal applying device connected between a cable and subscribers' terminal units in a CATV system, a signal for scrambling the video signal is produced in a time sharing mode, with the time sharing period being not uniform, and with sound disturbing long periods being mixedly interposed...http://www.google.de/patents/US4737990?utm_source=gb-gplus-sharePatent US4737990 - Unauthorized channel jamming signal applying method for CATV system
