Which type of controller is designed for basic zone control using a standard wall-mounted temperature sensor?

• A. Unitary controller.
• B. Air handling unit controller.
• C. Universal input-output controller.
• D. Application-specific controller.

Answer: (A)

Basic zone control uses a compact, self-contained control loop that reads room temperature from a standard wall thermostat and drives a single output to maintain the setpoint. A unitary controller is designed for exactly this role: it provides the sensing, control logic, and actuator output in one package for a single zone, using a common wall-mounted temperature sensor. The other types are more specialized or broader in scope: an air handling unit controller governs an AHU with fans and dampers and multiple zones; a universal input-output controller offers flexible I/O for various sensors and actuators but isn’t inherently tailored to simple, single-zone thermostat control; an application-specific controller is customized for a particular system or process, which isn’t necessary for basic zone control. So, the best fit is the unitary controller.