Telephone Silencer

Posted on Jul 13, 2012

If you are busy and cannot answer or do not wish to answer your phone, this circuit will give a busy signal without you

Telephone Silencer
Click here to download the full size of the above Circuit.

having to leave the phone off the hook. After a predetermined time, the circuit is deactivated. U1 forms an astable multivibrator that can be set for a time up to 10 minutes by values of R3 and C3. When SI A is depressed, U1 starts, and Ql latches, which powers the circuit. At the end of a time interval determined by R3 and C3, Q2 and Q3 cut off and remove power from the circuit. During the operation, S3 throws a 150- resistor across the phone line, which simulates an off-hook condition.

Leave Comment

characters left:

New Circuits



Popular Circuits

Intruder Alarm
Homebrew tapeless camera
lamp dimmer circuit
dc tesla coil
Police Car Lights with LEDs
Active Audio Tone Control Circuit Design
Vegetable greenhouse temperature detection control circuit