This is one of my most attracted circuit published in Electronics For You years back. But still it is in limelight .More than 200 students selected the circuit as their engineering project. It detects an active mobile phone even in the silent mode and beeps. It’s range is 2 meters radius. It is ideal to monitor Mobile phone restricted areas like Examination hall and Confidential rooms. It detects, Incoming and Outgoing calls, SMS, MMS, Video capturing, Photo capturing etc. I have slightly modified the circuit to increase its range. Check this updated page to get full details including the project report and video of the circuit.