Allen-Bradley 1756-CNBR ControlLogix Communication Module

The Allen‑Bradley 1756-CNBR ControlLogix Communication Module is a ControlNet interface card for ControlLogix controllers that bridges the controller backplane to a ControlNet network and enables data exchange with remote I/O devices. The CNBR variant adds redundancy with two BNC connectors for ControlNet media and a Network Access Port (NAP) RJ‑45 with shield, providing primary and redundant media paths. It can be installed as a local head communication module or as the head of a distributed I/O rack, and it is powered directly from the ControlLogix backplane. The module weighs about 0.7 lb (0.3 kg). Operating temperature ranges from 0 to 60 C (32 to 140 F), with storage ratings down to -40 to 85 C and 5–95% relative humidity (non-condensing). These features support reliable ControlNet communication in ControlLogix systems, especially where media redundancy is desired.