This circuit can detect only electrical wires connected to the mains (live wire). It has an LED for visual signalization and a buzzer for audio. As the electrician places the detector closer to the electrical wire the LED will flash at a higher frequency.
As you can see the schematic of the wire detector circuit is quite simple. The first stage has the antenna in base of T1; capacitor C1 is used for filtering parasite high frequency signals which are captured by the antenna.
The low freq signal is captured through C4 and is applied to the amplifier stage (T2) and then to the pulse shape filter made with R10, R11, C3 and T3, T4 and T5. The final stage (T5) is a current amplifier for the LED or you can place a buzzer too.
The antenna is a pcb loop that look like in the schematic with length of 50 mm and width of 20 mm. The trace width has 4 mm.
Wire detector testing and adjustments
Connect the 9V battery and place the circuit close to a electrical wire that is connected to the main volage. Adjust P1 rotating the cursor to the left completely. Press the push-button and the LED should start flashing. Now adjust P1 until LED is dim. In this moment the detector circuit is set to maximum sensitivity.
Wire detector specifications