The PACSystems RSTi (now under Emerson) is GE’s answer to modular, Profinet‑centric remote I/O. It features compact DIN‑rail‑mounted modules with dual Ethernet ports, hot‑swap capability and robust diagnostics. The system supports a broad range of I/O types, including safety and specialty modules, and integrates with multiple fieldbus adapters. While RSTi brings modern capabilities, it still requires proprietary software and can be pricey. If you’re already committed to PACSystems, it’s a logical choice; if not, you may find comparable, more open I/O solutions elsewhere.