The sound active control circuit.

The sound active control circuit -- Using the sound to active the relay to drive the load.

Mic → Pre amp → CR Differential circuit → Schmitt circuit → Rectifier and filter → Toggle flip flop → bjt and relay

R8 -- increasing the input resistance of Q2.
C4,R6 -- Limited the frequency of sound.
CR Differential circuit -- Narrow the width of wave.
Schmitt inverter -- Converting the sound wave to square wave.
Rectifier and filter -- Diode and capacitor used to converting a series of square wave to one pulse.
Toggle flip flop -- Using CD4013 d flip flop as a toggle flip flop.
C3,R3,D3 -- Interference filter to make sure the flip flop of Q clear to zero when the power up.
The rest of schmitt inverters -- If the drawing current of relay is not that much as less 60mA, then it could be used the rest of inverters of 74HC14 to replace the bjt to drive the relay.
R4 -- It can be using smaller to get more Ic current of Q1 to drive the relay.

This circuit is very sensitive, because I didn't design the delay time during two sound, it is easy to active when the sound was detected.

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