Which statement best describes a peripheral device in automation systems?

• A. A device that processes data inside a central computer.
• B. A device that stores data in cloud storage.
• C. A device that is connected to a PC or building automation system controller to perform a specific function.
• D. A device that generates power for sensors.

Answer: (C)

In automation, a peripheral device is a hardware item that connects to a central controller to carry out a specific task. These devices extend the system’s capabilities by providing sensing, actuation, or signal conditioning, and they rely on the controller to decide what to do. They don’t process data themselves inside the central computer; instead, they execute commands or measurements as directed by the controller.

For example, a temperature sensor or a valve actuator is a peripheral because it plugs into the controller and performs a function that supports the system’s control logic. They’re connected via appropriate communication or I/O interfaces and send data back or receive control signals.

The other descriptions don’t fit because processing inside the central computer is what the controller does, cloud storage is about where data is kept rather than a device that performs a function in the control loop, and a device that generates power isn’t performing a control action. The essential idea is a device wired to the controller to execute a specific function.