Output TTL level can be detected with the microcontroller. The power supply can be 3-5V Can also access PLC24V level Then the PLC input terminal of the PLC COM power supply 24V input termination of the board signal output OUT, optocoupler board GND power negative Blue 2P 5.0 terminal connected to 220V voltage 3P terminal connected to the microcontroller input. Specification: 1.Board Size:73x15mm 2.Functuon:Testing whether AC 220V is existed colour: green Material: plastic Package Contents: 5 x Optocoupler Isolation Module warning: When the power module in the power of the board after the white wire frame can not Contact any device .. because it is high voltage. Note the of electricity. Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.