Allen-Bradley 1771-IA Programmable Logic Controller Module

The Allen-Bradley 1771-IA is an eight-point digital input module for the 1771 I/O family, designed to interface external switches and sensors with a PLC-2 controller through a 1771 backplane. It provides eight discrete input channels that accept nominal 120 V AC or DC signals, with a per-channel current rating around 75 mA, enabling direct reading of on/off devices in industrial environments. As part of the Series C 1771 I/O lineup, the 1771-IA supports standard 1771 backplane addressing in compatible chassis and can be configured for half-slot, 1-slot, or 2-slot addressing within chassis A or B. This module is commonly used to monitor binary sensors such as limit switches, door switches, and other digital devices to feed the PLC with real-time input status for discrete control and monitoring tasks in factory automation. With its eight input points in a compact form factor, the 1771-IA helps consolidate wiring and simplify panel layouts while maintaining compatibility with legacy PLC-2 configurations and the broader 1771 I/O ecosystem.