Central direct digital control systems are typically used for supervisory control instead of closed loop control. Which option expresses this?

• A. Supervisory control instead of closed loop control.
• B. Direct local closed loop control at each device.
• C. Open-loop control with no feedback.
• D. Data logging only.

Answer: (A)

Central direct digital control systems operate by supervising the overall process rather than running every control loop at the device level. The central controller watches sensor data, makes coordinated decisions, and directs actions through other controllers or devices—providing oversight, sequencing, alarms, and setpoint management. That supervisory role is what the option captures: it states that supervisory control is used instead of implementing closed-loop control at each device. The other ideas describe scenarios that don’t match how central supervision works: local closed-loop control at each device would shift the control effort to the devices themselves; open-loop control has no feedback to correct errors; and data logging only does not perform any control action.