| 摘要 |
PURPOSE:To exercise stable control while holding constant a relation with noise, by sending a control signal to set volume to a voice controlling circuit corresponding to the ambient noise when there is no voice input to be broadcasted, by twining to OFF a control input when a voice arrives, and by broadcasting with the volume set right before the sound arrives. CONSTITUTION:An ambient noise is acquired by noise microphone 2, whose signal is amplified by amplifier 3 of noise detecting circuit part 1 and then rectified by rectifying circuit 4 into a DC signal. Then, its output is charged in capacitor 6 of storage part 3 and then supplied as a gain control signal to broadcast sound input amplification part 7. When a sound arrives at broadcasting microphone 10, on the other hand, the signal is rectified by rectifying circuit 12 and normally closed contact 14b is opened by driving relay 14 to apply the charged voltage of capacitor 6 to amplification part 7 as a bias. Then, normally open contact 14a is closed and a sound amplified by amplifier 15 is applied to amplifier 7 to control the gain of amplifier 7 with the bias of capacitor 6, so that stable control is done by keeping the relation to noise constant. |
