GW 01 02 R is a Ring Redundancy Protocol Converter. In a RS485 network, 32 devices can be multidropped. Since this loop can travel upto 1.2km, there are many chances that there may be a cable break, causing the communication of the later devices to stop. You end up losing critical data. Redundancy in a 485 multidrop loop is not possible
The Redundancy scheme involves both these RS485 ports along with a specially designed firmware. GW 01 02 R also provide Modbus RTU to Modbus TCP conversion.