An apparatus with specified video carrier jamming for disturbing the image on a screen of a TV receiver for Fee-charged Viewing Thereof comprises an oscillating circuit, a switch means, a feeding device and a mixer circuit, and the said mixer circuit combines a video carrier with the output of said oscillating...http://www.google.ca/patents/US4085422?utm_source=gb-gplus-sharePatent US4085422 - Fee-charging apparatus for television sets
