What are the two states of a controller?

• A. Automatic and Manual
• B. On and Off
• C. Standby and Active
• D. Local and Remote

Answer: (A)

Controllers operate in two modes: automatic and manual. In automatic mode, the controller continuously measures the process variable, compares it to the setpoint, and automatically computes the manipulated variable to steer the process toward the desired value using its control algorithm (like PID). In manual mode, the operator overrides the automatic logic and directly sets the output, which is useful during tuning, commissioning, or abnormal conditions. Other terms like On/Off describe a power state, Standby/Active isn’t the standard control-mode terminology, and Local/Remote refers to where control is performed rather than how the controller determines its output.