Allen-Bradley 1747-L20A SLC PLC Processor Module

The Allen-Bradley 1747-L20A is a fixed-hardware SLC 500 processor unit that provides a compact 20-point I/O footprint: 12 inputs at 120 VAC and 8 AC/DC relay outputs, all powered from a 120/240 VAC supply. It includes 1K words of user memory, executes ladder logic programmed in the RS-Logix 500 environment, and is commonly programmed via the 1747-PT1 handheld terminal for field updates. Its physical form measures about 5.72 in W x 1.37 in D x 5.15 in H and weighs roughly 0.37 lb, with a 0–60 C operating range. The module supports DH-485 communications and is suitable for small to mid-size automation tasks requiring relay-based I/O and straightforward integration into an SLC 500 rack; high-speed counter capability is not provided on this model. A Belden 9463 cable is a typical connectivity option for processor-to-I/O linkage in many installations. The 1747-L20A is designed to be compatible with standard SLC 500 fixed-hardware chassis and can be expanded with compatible I/O modules to scale the control system as needed.