Allen-Bradley 1747-L20C SLC 500 Digital I/O Module

The Allen-Bradley 1747-L20C is a 20-point SLC 500 fixed-controller processor unit that integrates 12 digital inputs (24 V DC, sink) and eight relay-contact outputs in a single module for backplane-based control. It provides 1K words of user memory and DH-485 communications, enabling straightforward networking with other SLC 500 devices. The unit is powered from 120/240 V AC line power and requires up to 200 mA from a 24 V DC supply to power its on-board logic. This configuration is well-suited for compact discrete-control tasks such as small machines or packaging lines, where the 12 inputs monitor sensors or limit switches and the eight relay outputs drive relays or contactors. As a member of the SLC 500 family, the 1747-L20C supports legacy automation architectures and integrates with Rockwell Automation software environments designed for these fixed-controller systems.