Allen-Bradley 1747-L20B SLC 500 Processor Module

The Allen-Bradley 1747-L20B SLC 500 Processor Module is a fixed‑hardware PLC processor in the SLC 500 family, designed for compact machine control. It provides 20 I/O points in a single module, featuring 12 inputs that accept 120 VAC signals and eight triac outputs for switching AC loads. Firmware revision FRN 6 is associated with this model. Built for use in 1747 backplane systems, the L20B is programmed with Rockwell Automation’s RSLogix 500 ladder logic to implement discrete control, sequencing, and interlock tasks. This processor is commonly employed in small‑to‑mid sized automation tasks where a 12‑in/8‑out footprint suffices, such as simple machinery controls, conveyors, and packaging line segments. In typical installations, it operates alongside other 1747-series I/O modules within a rack, enabling straightforward, reliable control of AC loads through fixed I/O points.