Voice-activated recording circuit (2)

Working principle of the circuit: When a sound wave compresses the electret microphone M IC , the M IC can
output a weak audio signal, which is sent to the non-gate linear amplification circuit for continuous amplification.
If the waveform peak distortion is not considered, the signal amplitude output by F3 is large enough, this signal passes through c.
After coupling, VD. , VD2 rectifies to obtain unipolar pulses to charge c5. % is very fast,
greater than 1/2 VDO, the output of NOT gate F4 is 0, the output of B is 1, and the high level goes to C. Charging,
vc8 also quickly exceeds l/2 VDI, F6 output is O, transistor VT is saturated and conducts,
vs is triggered, so 220 V mains power supplies power to the recorder through socket xs , and recording
starts ; if the sound disappears, C, the upper voltage cannot be maintained, and va quickly drops to 0. Similarly,
c8 can only slowly discharge to R8, and vc8 drops to 0 after about 3 seconds. At this time, vs is cut off
and the recorder stops recording; in this way, automatic recording control of recording is achieved (if
a longer delay is required, the value can be increased appropriately. large cs capacity).