Allen-Bradley 1771-LI Loop Controller Interface Module

The Allen-Bradley 1771-LI Loop Controller Interface Module is a PLC-5 compatible interface that provides a dedicated RS-485 twisted-pair link between a central PLC processor and up to 15 1771-LC Loop Controllers. It mounts in a single 1771 I/O chassis slot and communicates at 4,800 bits per second, enabling timely exchange of control data between the PLC and the loop controllers. The module draws 1.3 A from the backplane and is powered from a 5 VDC supply, delivering reliable loop-control communications within a PLC-5 system. In operation, the 1771-LI transmits setpoints from the PLC to the loop controllers while returning loop status, measurements, and control signals for centralized monitoring and adjustment. This configuration is ideal for distributed analog control across processes requiring multiple loop controllers—such as temperature, pressure, flow, or level control—where scalable, coordinated loop management is essential and where a single interface must reliably manage communication to several 1771-LC devices.