Metal detector circuit electronic project

This metal detector circuit electronic project is an very simple circuit that is based on common electronic parts .
This metal detector circuit is based on transistors and will provide an visual indication using a LED and an acoustic sound that will inform you when a metal is detected .

This metal detector must be powered from a simple 9 volt battery an it needs some little adjustments.
To adjust these circuit you need to power it on and move it away from any metal object .
You must turn RV2 potentiometer fully clockwise and RV2 potentiometer anti-clockwise.

With SW1pressed you must turn RV1 anti-clockwise until the LED is about to light and all further sensitivity adjustments should now be done by turning RV2 . To set maximum sensitivity , turn RV2 until the LED is weakly lit. The brightness of the Led indicates the distance and the size of the metal object detected .
The L1 and L2 coil must be on the same support that must have a 8mm diameter . L1 has 120 turns from 0.3mm Cu wire and L2 has 43 turns from 0.3mm Cu wire .