1
Shiu H Cheung: Television audience measuring system. Kinzer Plyer Dorn & McEachran, March 24, 1981: US04258386 (224 worldwide citation)

Apparatus for television audience analysis comprising means for monitoring a television receiver, means responsive to a monitored signal for storing information representative of channel identification and of the time at which a channel is selected and at which the selection of a channel is terminat ...


2
Shiu H Cheung: Pay TV system. Kinzer Plyer Dorn & McEachran, January 13, 1981: US04245246 (103 worldwide citation)

An apparatus for coding video information arranged in a plurality of lines comprises means for selectively inverting video information in groups of lines. A random timing device controls the number of lines in successive groups. The video signals in one group are inverted and the video signals in th ...