Electronic phone bell

Posted on Sep 15, 2012

The speaker emits a distinctive warble tone when ring pulses are applied to the phone line. Use this circuit as a remote bell or disconnect the phone`s ringer for direct use. Rl adjusts the duration of the output; R2 and R3 control the tone`s duty cycle and frequency. The transistor is a general-purpose NPN photodevice

Electronic phone bell
Click here to download the full size of the above Circuit.

The neon bulb and transistor are coupled with the heat-shrink tubing to form an optoisolator.

Leave Comment

characters left:

New Circuits



Popular Circuits

Simple 2M 6M Transverter Circuit
Fireflies based on tiny AVR
Camera Switch Circuit using 4017
Photodiode Alarm
3V to 24V Variable Power Supply
Discrete components sound and light control stairs delay switch circuit 8