Cable television with controlled signal substitution

Abstract

A signal substitution system for cable television applies substitute television program signals in at least one substitute channel to the transmission cable along with singal substitution control signals. The signal substitution control signals include a plurality of different terminal command signals and a plurality of different event command signals, each of the terminal command signals including a respective panelist address signal for identifying a respective panelist receiving station, and each of the event command signals including a normal channel identification signal for identifying a normal channel into which a substitute television program is to be switched. A controller at each panelist receiving station responds to the signal substitution control signals by selectively switching a substitute television program into a normal channel. The controller includes a generator of a local panelist address signal and a substitute channel selector for producing a substitute channel select signal corresponding to a substitute channel. A first comparator compares the received panelist address signal of each terminal command signal with the local panelist address signal and produces a first match signal when the signals match. A second comparator compares the received normal channel identification signal with a channel select signal selected by the viewer and produces a second match signal when the signals match. In response to the first and second match signals a substitute channel is substituted for the channel selected by the viewer for a period determined by the signal substitution control signals.