Allen-Bradley 1756-DHRIO DH RIO Interface Module

The Allen-Bradley 1756-DHRIO is a two‑channel DH+/RIO Bridge/Scanner module for ControlLogix that sits in a 1756 backplane to connect legacy DH+ and Remote I/O networks to a modern ControlLogix system. Channel A handles DH+ traffic while Channel B carries Remote I/O data, enabling bidirectional message routing between a DH+ network and Remote I/O endpoints through the ControlLogix controller. The unit provides three terminal blocks and supports dual‑channel operation, letting you bridge between DH+ devices and RIO I/O or other DH+/RIO paths without additional adapters. It is used to exchange data with legacy DH+ devices and RIO racks via MSG-style communications while housed in a 1756 chassis. Rockwell Automation discontinued the 1756-DHRIO as of December 31, 2024; existing installations may still rely on this module where replacements are needed.