What type of control is connected directly to the sensors and actuators that it communicates with?

• A. Direct digital controller (DDC)
• B. Programmable logic controller (PLC)
• C. Distributed control system (DCS)
• D. Smart thermostat

Answer: (A)

Field-level digital control is what this item is about: the device that sits directly at the sensors and actuators it controls, running the control logic locally and communicating with the rest of the system. That role is filled by a Direct Digital Controller. It wires directly into sensors like temperature or humidity sensors and to actuators such as dampers, valves, and relays, handling the control loops on the spot and sharing data with the building automation network. A programmable logic controller is a versatile industrial controller that can connect to field devices but is used across a broader range of processes and environments; a distributed control system involves many controllers spread across a plant with a central supervision layer, not typically the single device that directly interfaces with every field device in a building; and a smart thermostat is a single-zone, consumer-focused device, not the field-level controller for an entire BAS.