| 摘要 |
PURPOSE:To prevent a momentary increase in sound volume and the generation of noise due to the operation stop of a high frequency circuit by attenuating the output signal of a low-frequency amplifier according to the operation state of the high-frequency oscillation circuit of a microphone device. CONSTITUTION:A resistance R1 and a capacitor C1 in the microphone device constitute the power source decoupling of an audio amplifier 103, and a resistance R2 and a capacitor C2 constitute the power source decoupling of high-frequency circuits 104-106. When a push button 110 is released during simultaneous sound recording and photography to open a switch 109, the capacitor C2 of the high-frequency oscillation circuit is discharged instantaneously and a relay contact is broken to stop the photography of a camera immediately. On the other hand, the base potential of a transistor TRQ1 drops by the discharging of the capacitor C2 to turn on the TRQ1, and then a TRQ2 also turns off. Therefore, the output signal of an amplifier 103 is attenuated by a resistance R3 and the TRQ2 and its supply to a modulator 105 is cut off right after the switch 109 is released. |
