| 摘要 |
PURPOSE:To prevent a noise of a changeover switch and malfunction of a TV sound multiplex display device due to MPX operation by stopping an input signal of an FM stereo display LED drive circuit at FM stereo reception. CONSTITUTION:When a TV sound multiplex signal is inputted to a detection output terminal 1, the signal is demodulated by a TV/MPX7 and outputted to a changeover switch 3. In this case, the TV/MPX7 drives LEDs 5, 6 and the output of the TV/MPX7 is outputted to a terminal 4 through a diode 11. Since the LEDs 5, 6 are not driven at monaural signal, a signal at an FM/MPX2 is outputted. The FM stereo signal is demodulated by the FM/MPX2 and outputted to the changeover switch 3. The FM/MPX2 drives an LED9 and cuts off an amplifier 8 and since no input is given to the TV/MPX7, the TV/ MPX7 acts like preventing malfunction of the LEDs 5, 6 and noises due to the changeover switch 3.
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