phone busy circuit

Posted on Feb 7, 2014

Have you ever been using the modem or fax and someone else picks up the phone, breaking the connection Well, this simple circuit should put an end to that. It signals that the phone is in use by lighting a red LED. When the phone is not in use, a green LED is lit. It needs no external power and can be connected anywhere on the phone line, even mo

phone busy circuit
Click here to download the full size of the above Circuit.

unted inside the phone.

Leave Comment

characters left:

Related Circuits

  • New Circuits



    Popular Circuits

    Mini 10W Amplifier
    Auto poweroff for power supplies circuit
    Dual Litz Honeycomb Coils Crystal Radio
    Fog Lamp Sensor Circuit
    DIY 6T9 Tube (Valve) Single-Ended Amplifier Kit
    3 voltmeter method of measuring choke
    Simple Transistor Amplifier Circuit Schematic and Explanation
    DIY Intercom Design Thread 4
    XTR108 VREF driven by the excitation circuit diagram of the bridge