Control Panel only x Control Panel + Remote I/O

[leomiranda]

Generally in the projects of my company we provide just one Control Panel to control our skid, all instruments signals (AI, DI) go directly to this CP (Control Panel) and our PLC communicates with the OIL Rig master PLC. But in one client standard I saw this information that we must follow: “Local Control Panel with Remote I/O cabinet (Remote I/O if required)”.
When a remote I/O cabinet turns necessary to be used (Control Panel + Remote I/O Panel)?
Sorry for my dumb question, but I don’t work with automation!