| 摘要 |
PURPOSE:To prevent a noise from being generated in intercepting a voice, by controlling the operation of a muting circuit on the basis of the absolute level of the output of a tuner and a muting command. CONSTITUTION:A sound level detecting circuit 6, when the absolute level of the output of a tuner 2 is nearly zero, supplies a high-level signal to one input of an AND gate 7. On inputting a muting command signal, a control part 8 places a mutig signal in a stand-by state and supplies a signal showing the stand-by state to the other input of the AND gate 7. Then, the output of the AND gate 7 releases the stand-by state of the control part 8. Therefore, even when the muting command signal is outputted, it is not supplied to a muting circuit 3 immediately and after the absolute level of the output of the tuner 2 is judged to be nearly zero, it is supplied. |
