Cell phone detector project is one of the best mini project in electronics engineering branch because it tell how communication can be interrupt and which band of frequencies are being used. In mobile communication, generally in GSM technology, there is two type of frequencies band that are used. One is call baseband frequency through which voice our data is being transmitted and other is frequency is called as signalling frequency through which signalling is done like call connection, call hold, call waiting etc. signalling frequency is low frequency band and the baseband is a high frequency band. In Cell phone detector project, we make a circuit which is oscillating at signalling frequency band and which any same frequency is found near it it, this circuit become is resonance mode and high current or voltage is generated at the output.