General Electric IC687RCM711 Redundancy Communications Module

The GE IC687RCM711 is a specialized hardware solution for high-availability automation. This module enables Hot Standby (HSB) configurations within the Series 90-70 PLC ecosystem. It creates a dedicated synchronization link between primary and secondary processors. Consequently, the system maintains continuous control during hardware or software transitions. This functionality remains vital for industries where downtime causes significant financial or safety risks.

Advanced System Synchronization

The module manages high-speed data transfers to keep the backup CPU updated. It operates at 500 KB/s to ensure both processors remain in exact lockstep. Because of this rapid exchange, the backup unit assumes control instantly if the master fails. The hardware manages the transfer of internal registers and I/O states automatically. This process eliminates the need for complex custom synchronization code.

Furthermore, the unit features a rugged internal design for industrial environments. It draws power directly from the 5V PLC backplane. This configuration simplifies installation by removing the need for external power supplies.

Interface and Manual Overrides

The front panel provides immediate visual feedback through five green LED indicators. These lights track the status of the local module and the remote link. Additionally, they confirm whether the associated CPU is currently active or in standby mode.

Operators can use the integrated physical pushbutton for manual maintenance tasks. This button triggers a controlled switchover between the redundant processor pair. However, the system requires a short stabilization period before reversing the control direction. This safeguard ensures that the receiving CPU is fully synchronized before accepting the load.

Application and Installation

Engineers typically deploy the IC687RCM711 in mission-critical Distributed Control Systems (DCS). It supports distance requirements of up to 15 meters between redundant racks. This allows for flexible cabinet layouts in large control rooms. The module fits into a single slot, which optimizes rack space for additional I/O. Proper grounding and shielded cabling ensure signal integrity across the redundancy link.

Technical Specifications