Cell Phone Detector

Circuit Projects has made a sort of pointless yet cool gadget... a cellphone detector. It is a pretty basic project as long as you have some decent soldering skills. However, the detector can only pickup signals and not the actual conversation since the signals are encrypted. Below the picture is the complete list from the website

R1, R5 : 100K 1/4W Resistor
R2, R6 : 1k 1/4W Resistor
R3, R7 : 8.2M 1/4W Resistor
R4, R8 : 220 Ohm 1/4W Resistor
R9 : 2.2K 1/4W Resistor
D1, D2 : BAT43 Schottky Diode
C1, C2, C4 : 100nF Polyester Capacitor
C3 : 100uF 16V Electrolytic Capacitor
L1, L2 : See Text
U1 : LM358
J1 : 8 Pin Socket
J2 : Stereo Jack
1 x 9V Battery
1 x 9V Battery Socket
1 x LED
1 x On/Off Switch