The multiple broadcasting of TV sound is the stereo broadcasting of TV sound. Figure 7-71 is a block diagram of a transmitter for multiple broadcasts of a TV sound. The sum signal is sent as the main channel signal, and the difference signal passes through the limiter, IDC circuit, and low-pass filter as the sub-channel signal. After synthesis, it is sent to the sound transmitter.
Transmitter block diagram of TV sound multiplex broadcasting
At the receiving end, the block diagram of the sound processing circuit in the TV is shown in Figure 7-72. Detect the output of the image, take out the intermediate frequency of the sound, amplify it and then discriminate the frequency to obtain the composite sound signal. It contains the main channel signal, sub-channel signal and control signal. This composite signal can be processed and converted to obtain a stereo sound output. 
Block diagram of TV sound processing circuit
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