Mobile incoming call indicator

This circuit can be used to escape from the nuisance of mobile phone rings when you are at home. This circuit will give a visual indication if placed near a mobile phone even if the ringer is deactivated.

              When a call is coming to the mobile phone, the transmitter inside it becomes activated. The  frequency of the transmitter is around 900MHz.The  coil L1 picks up these oscillations by induction and feds it to the base of Q1. This makes the transistor Q1 activated.Since the Collector of Q1 is connected to the pin 2 of IC1 (NE555) , the IC1 is triggered to make the LED connected at  its output pin (pin 3) to blink. The blinking of the LED is the indication of incoming call.

Circuit diagram with Parts list.


  • The coil L1 can be made by making 150 turns of 36 SWG enameled copper wire on a 5mm dia plastic former.Or you can purchase a 10 uH coil from shop if available
  • The circuit can be powered from a 6V battery
  • Assemble the circuit on a good quality PCB.
  • C1 & C3 are to be polyester  capacitors
  • The electrolytic capacitor C2 must be rated 10V


  1. Anonymous said...:

    hi sir,
    i m doing this project by using 10uH coil which looks like a resistor.
    after applying 6v (using four 1.5v cell in series)supply to it LED blow up

  1. SUMIR said...:

    Hello, Friend

    I have uploaded the corrected version of same circuit....

    I have made some minor changes at the Pin 3 of IC555.
    Now It will work perfectly

    View Images:-

    Follow the above link and see the circuit

  1. bradley blunt said...:

    hello. I would to attempt this project but i have no idea how this would look like or how it would go together on a strip board. please help.

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