A Simple Electronic Buzzer electronic

the circuit is very simple , it just uses a couple of resistors, a capacitor and the easily available 555 timer IC. The 555 is setup as an astable multivibrator operating at a frequency of about 1kHz that produces a shrill noise when switched on.

A Simple Electronic Buzzer electronic

The frequency can be changed by varying the 10K resistor.

Trigger Input Control Of 555 Timers

The following method allows the timer to be triggered by a normally closed switch. This would be useful in applications such as intrusion alarms where the protection circuit is broken if a window or door is opened Trigger Input Control Of 555 Timers