| 摘要 |
PURPOSE:To prevent a mulfunction in an overmodulation state, by providing an amplitude detecting circuit for detecting a modulation level of a detection output signal, and a gate circuit. CONSTITUTION:A detection output signal (voice signal) from a detection output signal source 1 is provided to a high-pass filter 2, an amplitude detecting circuit 7 and a noise reducing circuit 8. Only a noise component exceeding a voice signal band is taken out by the filter 2, is provided to a rectifying circuit 6 through an AGC circuit 3, an amplifying circuit 4 and a gate circuit 5, a DC output signal is obtained, and the noise reducing circuit 8 is controlled by this DC signal level. Also, a noise level (modulation level) in case when modulation is slight is detected in advance by the amplitude detecting circuit 7, and when the gate circuit 5 is controlled by this level, a DC signal which has removed an overmodulation noise is obtained from the rectifying circuit 6, and a malfunction in an overmodulation state is prevented by controlling the noise reducing circuit 8 by this DC signal. |
