Patent ID: 6952237

Claim:
An apparatus for transmitting an audio signal over a dedicated video transmission line in a closed circuit television system comprising: a. a modulator having an audio input, a video input, and a first synchronization device all attached to a first switching device capable of toggling between said video input and said audio input, said first switching device having an output; b. a demodulator having an audio output, a video output, and a second synchronization device all attached to a second switching device capable of toggling between said video output and said audio output, said second switching device having an input; and c. a single transmission line connecting the output from said first switching device to the input of said second switching device wherein said first and second synchronization devices are identically synchronized with each other, audio signal samples are inserted into the endings of the active video scan lines of a video signal at regular intervals according to said first synchronization device through the toggling action of said first switching device in said modulator, and said audio signal samples are removed from the endings of the active video scan lines of the video signal at regular intervals according to said second synchronization device through the toggling action of said second switching device in said demodulator.