1、DETECT OUTPUT TTL LEVEL: The output TTL level can be detected by a microcontroller, power supply can be 3‑5V, can also be connected to PLC 24V level 2、PLC TERMINAL: When connecting to the PLC input terminal, the COM terminal of the PLC is connected to the 24V input terminal of the power supply, connect the signal output OUT of the board, and the GND on the optocoupler board is connected to the negative pole of the power supply 3、WITH 2P AND 3P TERMINAL: The green 2P 5.0 terminal is connected to 220V voltage, and the 3P terminal is connected to the input of the microcontroller 4、STABLE HIGH LOW LEVELS OUTPUT: Can be used to detect the existence of 220V AC power, and stably output high and low levels (NPN output) 5、LED LIGHT INDICATOR: When there is 220V input, the LED is on, the optocoupler is turned on and the output is low. When there is no 220V input, the LED is off, the optocoupler is not connected. The output is pulled high by the resistor