Series Five PLCs were designed as GE’s mid‑range controllers, combining features from the earlier Series One, Three and Six families. They use 6‑ or 8‑slot base units, modular CPUs and a range of I/O including analog and motion modules, and can expand to thousands of points using remote racks. Programming is via the vintage Logicmaster 5 software. While robust and modular, Series Five hardware is decades old and lacks Ethernet or modern programming environments. Keep it running if you must, but plan to replace it with a contemporary PAC.