| 摘要 |
PURPOSE:To obtain a monaural sound signal possible for demodulation in any mode by selecting only either one sound signal of a main and sub-sound signal from a received multiplex sound signal and applying the selected signal to a monaural RF modulator. CONSTITUTION:When the received signal is a multiplex sound signal, one channel signal, e.g., main sound signal is applied to an input terminal 19 and the other sub-sound signal is applied to an input terminal 20. A control signal applied to an input terminal 21 in this case turns on a switching circuit 22 so as to interrupt the terminal 20 and a mixing circuit 6. Thus, only the sound signal applied to the terminal 19 is applied to the RF modulator 7 through the circuit 6. Then even if signals of any mode are applied to the terminals 19, 20, a monaural sound signal producing a demodulated sound possible for listening is applied from an output terminal 8 to a TV receiver.
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