Allen-Bradley 1747-L551 CPU Module for SLC 500 PLC

The Allen-Bradley 1747-L551 SLC 500 CPU Module is a PLC CPU processor for SLC 500 (SLC 5/05) systems. Designed for chassis-mounted installation in an SLC 500 rack, it executes control logic, manages I/O, and provides Ethernet Channel 1 and RS-232 Channel 0 communication between field devices and networks. Key specs include 16K words of user memory, up to 4096 inputs and 4096 outputs, up to 480 analog I/O points, and as many as 32 simultaneous connections, with a scan time of approximately 0.9 ms per Kword and battery-backed RAM for memory backup. Part numbers listed are 1747-L551 / 1747-OS501, and common replacements include 1747-L552, 1747-L553, and 1769-L32E; the module is discontinued, though support and repair options remain available for industrial automation control and communication.