Allen-Bradley 1771-A2B SLC 500 PLC I/O Module

The Allen-Bradley 1771-A2B is an eight-slot universal I/O chassis for PLC-5 remote I/O networks, designed to accept 1771 I/O modules and to be powered by a compatible 1771-P4S power supply module. As an eight-wide backplane, it provides space for a mix of 1771 I/O cards and has external dimensions of roughly 35.6 cm (length) × 34.1 cm (width) × 3.05 cm (height). The chassis is used with PLC-5 remote I/O architectures and can connect to PLC-5 controllers through remote I/O adapters such as the 1771-ASB, enabling distributed I/O across a factory floor. It is not a standalone PLC processor; rather, it serves as the physical I/O backbone within a PLC-5 system, hosting standard 1771 I/O modules for input and output functions. Typical applications include expanding an existing PLC-5 control system with additional I/O points distributed across multiple remote locations on a manufacturing, packaging, or process automation line, while maintaining centralized control and straightforward wiring through the 1771 backplane scheme.