Allen Bradley 1747-L551 Ser C 1747-OS501 C FRN 11 SLC 500 5/05 CPU Processor 16K
(Surplus Unit Working Used 1747-L551 Ser C 1747-OS501 Ser C FRN 11. 16K words total 12K words for data or prog) 4K words for data). Allen Bradley SLC 500 1747L551 1747OS501 1747-L551/C Date Varies. While many Allen Bradley / Rockwell Automation products will have firmware already installed, we makes no representation as to whether a PLC product will or will not have firmware and, if it does have firmware, whether the firmware is the revision level that you need for your application or not.