diagram ingram

Mobile Incoming Call Indicator Circuit Diagram

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.
Notes:

•   
  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.