Various diagram

When the circuit at its close state, the IC will control the buzzer time using the resistor and capacitor. The buzzer sounds like alarm in the different frequencies.

•     Resistor R1 : 1.8k ohm
•     Resistor R2 : 1k ohm
•     Resistor R3 : 5.6k ohm
•     Resistor R4 : 480 ohm
•     Capacitor C1 : 2.2 nF
•     Polar Capacitor C2 : 0.022uF/6V
•     IC1 timer : NE555
•     Speaker SP1 : Tweeter 8 ohm
•     Power supply : 5V