Isolated RS485/232 interface board for Siemens S7-200 Smart PLC. Isolate RS485 and RS232 signals; Effectively solve the problems of ground loop interference and port burning caused by different ground potential of each RS485/232 node; Anti-lightning and anti-interference; Built-in RS485 terminal resistor (switch); Maximum communication distance: 1000m. Completely compatible with the Siemens non-isolated interface board SB CM01; Directly replaceable; Convenient to use.