The card takes the power switch circuit principle. Generally, the card power take-off switch has three parts: the high and low voltage power conversion part, the identification card part and the output part. Among them, the conversion of the power supply is in various ways, such as a switching power supply type, a RC capacitor, a transformer type, and the like.

The high-low voltage conversion part supplies the alternating current to the identification part and the output part through the rectification step-down to the DC low-voltage power supply.

The identification card section detects whether the inserted card conforms to the preset standard (mainly the second to eighth modes described above)

The output part receives the standard signal of the identification card part and turns on the AC power (fire line). This part has 30A, 40A, etc. according to different load requirements.