Wall wire detection circuit

This is the electrical schematic diagram of detection only. TX is a sensing piece, which induces an AC signal near the AC wire and sends it to the gate of
the junction N-channel field effect transistor VT1 . VT1 has half-wave rectification and amplification effects on AC signals. When there is no signal, the drain of VTI outputs high level , and VT2 and VT3 are both cut off. The LED doesn't light up.   In the negative half cycle of the signal. Make the gate of Tl more negative relative to the source. So the VT1 output is still high level. L.ED does not emit light; and when the signal is in the positive half cycle, VT1 outputs low level , and VT2. VT3 is turned on and the LED lights up. R2. R3 and e add bias voltage to VT1 to improve the sensitivity of detection.