Allen-Bradley 1785-L40B Programmable Logic Controller

The Allen-Bradley 1785-L40B Enhanced PLC-5 Controller is a mid-range PLC-5 CPU module designed to sit in 1771 I/O racks to execute control logic, manage I/O operations, and coordinate communication across industrial networks. It offers up to 48K words of user memory and supports up to 2048 I/O points, enabling sizable control schemes in manufacturing plants, material handling systems, process control, or machine automation. This PLC-5/40 series processor uses ladder logic programming and provides Data Highway Plus (DH+) / Remote I/O communication, plus a configurable RS-232/422/423 serial port for serial device integration. It supports multiple local and remote chassis, enabling scalable configurations within a single PLC-5 system. Common replacements include 1785-L60B and 1785-L80B, with compatibility reference to 1756-L61 in mixed-platform environments.