This entire circuit of beeper cum visual indicator is build and fabricated around two timer ICs and is configured in an astable multivibrator mode. The frequency generated by IC 1 is controlled by capacitor C 1 . The output from pin 3 of IC 1 is given to input pin 4 of IC 2 and base of voltage amplifier transistor T 1 through resistor R 4 . Flashing light is connected to collector of switching transistor T 2 and grounded through resistor R 7 . The output of IC 2 is obtained from pin 3 and is given to base of power amplifier transistor T 3 used to drive 8-ohm speaker connected to the collector. NOTE: LED can be replaced with 3V to 12V DC bulb after eliminating resistor R 7 . Beeper visual indicator Circuit Diagram PARTS LIST Resistors (all ¼-watt, ± 5% Carbon) R 1, R7 = 330 Ω R 2 = 6.8 KΩ R 3 = 5.6 KΩ R 4 = 47 KΩ R 5 , R 6 = 22 KΩ Capacitors C 1 = 100 µF/10V electrolytic C 2 , C 4 = 0.1 µF ceramic disc C 3 = 0.01 µF ceramic disc C 5 = 1000 µF/25V electrolytic Se...