This document describes a mobile phone detector circuit that can sense the presence of an activated mobile phone from 1.5 meters away. The circuit uses a tuned LC circuit to detect radio frequencies between 0.9-3GHz emitted by mobile phones. When a signal is detected, an LED will blink and a buzzer will sound. The circuit aims to prevent mobile phone use in places like exam halls or confidential meetings. It works by using a capacitor to capture phone signals and an op-amp to convert this to a voltage that triggers an alarm. Future plans include extending the detection range and adding a signal jamming function.