| 摘要 |
PURPOSE:To obtain a reproducing signal with high quality by detecting a level of a video signal component included in the sound signal and that of an audio signal of sub-channel demodulated to limit a pass frequency band of the audio signal. CONSTITUTION:A part of an output signal of a video intermediate frequency amplifier circuit 24 is applied to a phase modulating component detecting circuit 26. An output signal of the circuit 26 is detected and integrated by a video signal component level detecting circuit 27 and the 1st control signal is outputted. A sub-channel output of a demodulating circuit 10 is applied to a matrix circuit 11, and a part is applied to an LPF21. An output signal of the LPF21 is detected and integrated by an audio signal detecting circuit 22 and the 2nd control signal is outputted. The 1st and the 2nd control signals are applied to a reproducing band control circuit 28, and a switching control signal is applied to the circuit 28 from the circuit 10 at the same time. The circuit 28 outputs a control signal changing the reproducing band of a pass band variable filter 20 and the reproduced band of the filter 20 depends on the content of the sound multiplex signal. Thus, the reproduction with high quality is attained. |
