This is knock the melody. It uses begin flasher circuit in building sound click keen go up at a loudspeaker. But each time at Q2 (2N3906) work by origin frequency circuit that use RC and Q1(2N3904) ,R2 – 50K use fine work rate repeatedly through 20-280 sections time per minute.
By value change of C1 (22uF) will change the tone of voice in the sound click at happens.
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