Modbus Relay modules

1. VCC, GND: DC7-24V power input

2. IN, GND: DC3.3-30V optocoupler signal input

3. A +, B-: RS485 communication interface, A +, B- are connected to A +, B-

4. Relay switch signal output

NC: normally closed end, the relay is short-circuited to COM before pull-in, and left floating after pull-in;

COM: public end;

NO: Normally open, the relay is suspended before the pull-in, and shorted to COM after the pull-in.

5. Relay indicator: lit when the relay is on

6. GND, RXD, TXD: TTL level UART communication interface, GND, RXD, TXD are respectively connected to GND, TXD, RXD of the external control terminal