Phone Line In use LED with 2N2222

Posted on Aug 28, 2012

With this circuit mounted in or near every phone in the house, it will allow users to know if the phone is being used and not to pick up the phone. When a phone is taken off hook, the voltage across the tip and ring terminals drops to 10 volts or less. This will cause the FET (2N4360) to turn on and also turn on the transistor (2N2222). When the transistor turns on it will allow current to flow through the LED and make it light. A blinking LED could be used to make the effect better.

Phone Line In use LED with 2N2222
Click here to download the full size of the above Circuit.

Leave Comment

characters left:

New Circuits



Popular Circuits

Battery Charger
12 Volt Fluorescent Lamp circuits
Digital weight scale
LED Hat Display with Pong using an Arduino
Control motor PWM schematic
PARALLEL BUS REVEALED Conclusion of the first-ever PBI usage guide
Atari Punk Stepped Tone Generator
Flash Trigger
Ensemble RXTX Builders 2