RING BELL ELECTRONIC CIRCUIT USING NE555 DIAGRAM This circuit produces oscillating frequency around 1kHz, and able to be converted by changing the value of resistor R1. The speaker will produce a long beep sound with 1kHz frequency. Here is the schematic : Parts list : Resistor R1 : 10k ohm Resistor R2 : 56k ohm Capacitor C1-C2 : 0.01 uF Polar capacitor C3 : 1 uF/15V IC timer : NE 555 Speaker : 8 ohm 0.5 W ON/OFF switch 5-15V Power supply