The 1785-BEM PLC 5 Backup Communication Module is a backup communication module by PLC which is installed in a single I/O slot on the 1771 chassis and which allows for high-speed communication transfer between 2 connected PLC processors. The 1785-BEM backs up the processor’s data and information to prevent the loss of data in the instance of failure in the system. The module requires a backplane current of 0.6A at 5V DC, and it is capable of enabling the PLC-5 processors with 32-bit input capability on the processors image table. The 1785-BEM is designed with a switch assembly which consists of 4 switches set in varying positions, and it requires a field wiring arm (26-14 AWG) which has a wiring arm torque of 9 pounds-inches.
The 1785-BEM uses a copper wire with 26–14 AWG size as conductors, and it comes with the 1771-CD cable connector for DH+ and Remote I/O (RIO) communication. It has an HSSL communication speed of about 1.2 Mega Baud and it has a factory-built 0.25A relay at 24V DC (resistive). Keying to the backplane is achieved by a connection between pins 8 and 10 and pins 34 and 36 of the backplane top connector and it is CE, UL, and CSA-certified. The 1785-BEM has a factory-designated operating temperature range between 0 and 60 oC (32 and 140 oF) at a humidity range of 5-95% without condensation, and it has a storage temperature range of -40-85 oC (-40-185 oF).
