Remote control switching of television sources

Claim 1

Apparatus for transmitting command and control information from a central television programming source to one or more remote local television subscriber systems via encoded signals combined with video signals of a video program comprising, data generating means for developing binary command data messages, computer means for converting the binary command data messages into a pulse width modulated waveform representing the binary command data message, a shift register means having data and clock inputs operatively connected to said computer means said computer means loading said shift register means with a bit pattern that represents said pulse width modulated waveform, the number of shift register bits used to represent a particular data bit determining the width of the corresponding pulse in the waveform and hence its encoded value, a high speed clock means for shifting said waveform out of said shift register means, a sync detector circuit means for supplying sync information of said video signals to said computer means, said computer means responding to the vertical sync information by enabling said high speed clock means to shift said waveform from said shift register, and adder means for inserting said pulse waveform output from said shift register means into the vertical blanking interval of the video signal of the video program for transmission to the remote local television subscriber system, said pulse width modulated waveform consisting of narrow pulses and wide pulses, said computer means counting the logic zeros and logic ones in each binary command data message received from said data generating means and assigning the narrow pulses to represent the logic level which appears most often in the message and further including a mode bit in transmitted waveform to alert the local systems as to which pulse width corresponds to which logic level.