Allen-Bradley 1745-LP103 Programmable Logic Controller Processor Unit

Allen-Bradley 1745-LP103 SLC 100 Processor Unit is the fixed-base PLC processor module that combines the CPU, power supply, and a deterministic scan engine into a single enclosure for the SLC 100 family. The LP103 variant supports a total of 16 I/O points: ten discrete inputs and six discrete outputs, suitable for compact machine control tasks. It uses battery-backed CMOS RAM to store the ladder logic program, with a documented memory of 885 words, and provides an EEPROM memory module interface for program loading and data storage. A built-in expansion unit connection port enables attaching compatible 1745 expansion modules to extend I/O as needed. User interaction is facilitated by an Auto/Manual control switch and diagnostic LEDs, along with battery compartment and I/O status indicators for quick health checks. The unit supports AC input voltage configurations on its I/O lines, with input voltage options in the 85–132 VAC or 170–265 VAC ranges, aligning with the legacy SLC 100’s broad voltage tolerance. The LP103 is explicitly marketed as a 1745-LP103 Processor Unit for SLC 100 and, like other LP variants, is designed to operate within a fixed I/O base, without plug-in 1746-style I/O modules. This model is discontinued by the manufacturer, reflecting its retirement from current production while still commonly found in legacy automation and machine retrofits.