Field interface device is an electronic device that follows commands sent to the device from the CPU of a central-direct digital control system. Which option correctly defines this device?

• A. An accessory that stores historical data for reporting.
• B. An electronic device that follows commands sent to the device from the CPU of a central-direct digital control system.
• C. A wireless transceiver that broadcasts sensor readings to the cloud.
• D. A user interface for manual control of local actuators.

Answer: (B)

This item tests understanding of how a field interface device functions in a central Direct Digital Control system. The field interface device sits at the boundary between the control logic in the CPU and the field equipment. Its main job is to receive commands from the CPU and carry them out in the field, translating the CPU’s digital control signals into the appropriate actions or signals for sensors and actuators, and, when needed, sending field data back to the CPU in a usable form. This keeps the centralized controller in charge while the field devices operate correctly and safely.

The other descriptions describe different roles: storing historical data is a data recorder or historian, broadcasting sensor readings to the cloud is a telemetry or gateway function, and a user interface for manual control is an HMI used for local operator control. These functions don't capture the core duty of following CPU commands to drive field devices, which is what a field interface device does.