When entering the power supply circuit, and switch S1 (Start), which is attached press release switch off.Then current is flowing through R1, R2, and C2.
Makes the capacitor C2 caused up When the switch S1 allows the C2 to discharge through R3. The pressure this causes the clock input to the pin 8 of IC1a. The IC1a which will work with production IC1b frequency to send it to the leg 14 (Clock) Of IC2.The IC2 is a driver by ICs LED 10 is illuminated by the moon to the incoming frequency. The IC1d the IC1c and work together. It will serve up audio frequency generator, and then sent to the Piano Society (PZ1) loud beep came out with LED light period.
source:eleccircuit.com