Which of the following is an example of an INPUT device?

• A. Motor coil
• B. Pressure switch
• C. Red pilot light
• D. Auxiliary contact

Answer: (B)

An input device is something that provides information to the control system. A pressure switch detects a physical condition (pressure) and, once the setpoint is reached, changes its electrical state to send a signal to the controller. This makes it an input device because it supplies data about the process to the control system.

A motor coil is an output device because it uses electrical energy to create motion. A red pilot light is also an output device, indicating status to humans. An auxiliary contact is a secondary contact used within a control circuit to provide interlocking or feedback, and while it carries signals, it doesn’t by itself sense a process parameter.