| 摘要 |
An electronic circuit for automatically adjusting the sensitivity of a microphone in accordance with changes in ambient noise is disclosed. A signal is generated which is proportional to the magnitude of the ambient noise and is applied through a reverse biased diode to slowly charge a capacitor by means of leakage current. The capacitor is connected to a control input of a sensitivity control circuit connected between the microphone and a device. The sensitivity control circuit is responsive to the signal from the capacitor voltage signal for controlling the sensitivity of the microphone relative to the device. Because the capacitor is discharged at a rate which is much faster than the rate at which it is charged, the circuit sensitivity is raised more quickly in response to a decrease in the magnitude of the ambient noise than it is lowered in response to an increase in the magnitude of such noise. A similar circuit is disclosed for use with a microphone threshold circuit.
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