Allen-Bradley 1771-AL IO Adapter Module PLC-2

The Allen-Bradley 1771-AL is a PLC-2 local I/O adapter module that provides the interface between a PLC-2 controller and 1771 I/O chassis. This adapter enables the PLC-2 CPU to address and communicate with I/O modules mounted in 1771-series racks, acting as the local I/O link in classic AB control architectures. Designed for use with any 1771 I/O chassis, the 1771-AL preserves compatibility across the 1771 family and supports the standard backplane and bus addressing schemes used by PLC-2 systems. In practice, it is used to connect PLC-2 processors to distributed I/O modules for control of sensors, actuators, and simple industrial processes within environments that still rely on 1771-series remote I/O. The module’s purpose is to enable local I/O expansion and interconnection, without introducing new control capabilities on its own. When sourcing, verify that your system is a PLC-2 installation and that the 1771 I/O chassis is compatible with the 1771-AL adapter to ensure proper electrical and addressing compatibility in legacy automation setups.