The 1785-BCM PLC-5 is a Backup Communication Module made by Allen-Bradley and manufactured by Rockwell Automation. This backup module facilitates high-speed communication between multiple Programmable Logic Controllers from the PLC-5 family of processors. This backup communication module backs up the processor data in case of an unexpected system or power failure. This Allen-Bradley 1785-BCM PLC 5 Backup Communication Module occupies one slot on a 1771 Input/Output chassis, and the module is interoperable with both of the 5/60 and 5/80 range of PLC-5 processors. The 1785-BCM PLC-5 draws a 1 ampere backplane current at 5 Volts of Direct Current. The Allen-Bradley 1785-BCM PLC 5 Backup Communication Module comes with a Field Wiring Arm (Part Number 1771-WG) which has a screw torque of 9 inches-pounds. This wiring arm uses 26-14 American Wire Gauge (AWG) stranded or solid copper wire as a conductor.

The Allen-Bradley 1785-BCM PLC-5 Backup Communication Module requires a compatible connector cable (Part Number 1771-CD) in order to make use of its DH+ and Remote Input/Output capabilities. This Backup Communication Module can communicate on the HSSL Network at a rate of 1.2 Megabits per second. The Allen-Bradley 1785-BCM PLC 5 Backup Communication Module has an onboard relay with a current rating of 0.25 amperes at 24 Volts Direct Current (resistive). This module is keyed to the backplane through the connecting bands between pins 8 and 10, as well as backplane pins 34 and 36. The Allen-Bradley 1785-BCM PLC 5 Backup Communication Module can operate continuously without de-rating within the working temperature range of 32 degrees to 140 degrees Fahrenheit, or at a humidity ratio between 5% and 95% non-condensing. This module features a storage or non-operation temperature range of -40 degrees to 185 degrees Fahrenheit.

SLC 500 programmable controllers can be configured depending on the user needs. This family of modular hardware provides the opportunity to select suitable processor, power supply, and I/O modules depending on the user application and requirements. Amongst the variety of modules available for this family of controllers, 1785-BCM is a fast and reliable backup communication module which provides high-speed backup communication and switchover of the Data Highway Plus (DH+) and remote I/O links. The 1785-BCM is a part of the backup system which enables high-speed communication between two PLC-5 processors, should a fault occurs in the primary processor this module permits the secondary processor to take control of the process. The 1785-BCM module also provides high-speed transfer of data table values from the primary to the secondary system for backup purposes. This module provides a 4K words buffer for the data table values in case of any fault in the primary system. The module permits control to the secondary processor when the system experience any power failure, processor fault, or any change in the mode of operation. This module is compatible with PLC-5/15 Series B, as well as, -5/20, -5/25, -5/30, -5/40 and -5/60 processors. The power consumption of 1785-BCM is rated at 1 ampere at 5 volts DC. This module features UL and CSA Certifications.