Allen-Bradley 1771-A4B 16-Slot I Chassis Rack

The Allen-Bradley 1771-A4B is a 16-slot I/O chassis (rack) from the 1771 I/O family, designed to host up to sixteen modular I/O modules on a single backplane-backed chassis. This Series B assembly is a back-panel mountable, general‑purpose rack used within Allen‑Bradley 1771 I/O systems to organize and route signals between I/O modules and the controller. With sixteen slots, it provides a compact, scalable housing for a mix of input, output, and specialty modules, all sharing a common backplane for data transfer and addressable I/O. The designation 1771-A4B identifies its 16-slot configuration and its revision within the 1771 family, distinguishing it from earlier variants. Typical applications include industrial control setups that require modular, field-expandable I/O in a single chassis, simplifying wiring and maintenance by consolidating multiple I/O points in one rack.