- Record both modules’ switch settings and cable positions before disconnecting the backup pair.
- Restore matching PLC-5 application files before placing the primary and secondary processors back in service.
- Test normal transfer and forced switchover behavior after reconnecting the HSSL and relay wiring.
1785-BCM links the control responsibilities of two supported PLC-5 processors rather than operating as a standalone controller.
Its chassis interface, HSSL path, and external relay form the hardware layer used by the documented primary and secondary arrangement.
A service replacement should be evaluated as part of the entire backup pair, including processor catalogs, project files, wiring, and transfer behavior.
Availability, condition, price, and shipping time for 1785-BCM are confirmed during quotation.
Allen-Bradley 1785-BCM PLC-5 Backup Communication Module Manuals, Datasheets, Links
Important Notice: Other accessories, manuals, cables, calibration data, software, etc. are not included with this equipment unless listed in the above stock item description. All prices are shown in USD.
- The official compatibility list covers selected PLC-5/15 through PLC-5/60 processors.
- The module belongs in the local 1771 I/O chassis of the backup arrangement.
- Primary and secondary projects must represent the same documented machine strategy.
- The high-speed serial link communicates at the documented 1.2 Mbaud rate.
- Cable continuity and connector seating are essential to backup-partner communication.
- The customer relay can provide an external indication for the backup system.
- Confirm keying positions and the 1771-WG wiring arm before insertion.
- Restore the saved backup configuration before controlled switchover testing.
- Verify processor ownership, I/O response, and relay indication before production.
- Primary and secondary PLC-5 systems that require automatic transfer of control after a primary-processor fault
- PLC-5 backup architectures using the 1.2 Mbaud HSSL link between paired 1785-BCM modules
- Backup installations that use the customer relay for external status or switchover indication