Which statement best describes central supervisory control system?

• A. Decisions are made at a single central computer.
• B. It logs data but does not enable local controllers.
• C. Decision making equipment is located in various locations and the system enables/disables local controllers.
• D. It operates only with direct digital control at field devices.

Answer: (C)

In a central supervisory control system, decision-making is distributed across locations and the supervisory layer has the ability to manage the local controllers. This means there isn’t just one central computer making all decisions; instead, supervisory equipment spread across different sites coordinates actions and can enable or disable the local controllers as needed. This setup lets operators oversee multiple zones, respond to alarms, and implement high-level commands while the field controllers handle the actual process control. The other scenarios don’t capture that coordinating oversight: a single central computer would be truly centralized, data logging with no control actions misses the supervisory role, and relying only on direct digital control at field devices lacks the overarching supervisory layer that coordinates across locations.