Allen-Bradley 1747-L551 ENet RS-232 Controller

Allen‑Bradley 1747‑L551 is a SLC 5/05 CPU for the SLC 500 family that combines built‑in Ethernet and RS‑232 communications in a single modular controller. It provides 16,000 words of user memory and supports up to 4,096 I/O points, enabling it to run standard SLC 500 ladder logic programs while coordinating a mix of digital and analog modules in a compact chassis. The onboard RS‑232 port supports DF1 serial communications to peripheral devices, and the integrated Ethernet interface allows networked data exchange with host PCs, HMIs, or other controllers. As a long‑standing member of the SLC 500 ecosystem, the 1747‑L551 is typically installed in a compatible SLC 500 rack to manage I/O timing, sequencing, and remote communications across both serial and Ethernet networks. Note: Rockwell Automation announced the SLC 5/05 family, including the 1747‑L551, is discontinued for sale as of December 31, 2021.