The circuit uses a bridge rectifier circuit to convert AC into DC.
A 12v zener diode limits the operating voltage of the circuit to 12v. A tiny
Schmitt trigger inverter and a phototransistor detects the ambient light intensity.
If there is sufficient light, the inverter disables a push-pull oscillator circuit.
The oscillator, with a differential output, drives a charge pump circuit which when
activated, provides sufficient gate-source voltage to a pair of n-channel FETs to turn
them on fully. The transistor switch can handle both AC and DC with a current in
excess of 5 amps.