Allen-Bradley 1785-BCM Backup Communication Module

The Allen-Bradley 1785-BCM Backup Communication Module is a PLC-5 era redundant communications device that provides a high-availability path for DH+ (Data Highway Plus) and Remote I/O networks, enabling automatic switchover between primary and backup links to keep critical I/O updates flowing. Used with PLC-5 controllers, it commonly pairs with the 1785-BEM backup expansion module to support seamless failover and data integrity during network faults. The BCM is designed for installation in a PLC-5 chassis and supports DH+ communications and RIO bridging, preserving uninterrupted data exchange for I/O modules and remote devices when the main communication channel experiences interruptions. Typical applications include manufacturing lines and process-control systems where uninterrupted DH+ or RIO communications are essential. Supported PLC-5 processors include models in the L11B, L30B, L60B, and L80B families and other PLC-5 CPUs compatible with BCM configurations. Automatic switchover is a key capability, enabling the backup path to assume control without operator intervention and helping minimize downtime in mission-critical control loops.