A(n) __________ is an input switch that senses the position of a machine member by mechanical means and converts the position into an electrical signal.

• A. Limit switch
• B. Proximity switch
• C. Pressure switch
• D. Photoelectric switch

Answer: (A)

Position sensing with a mechanical actuator turning into a switch signal is what a limit switch does. It has a physical actuator—a lever, plunger, or cam follower—that is moved by a machine member at a defined position; when triggered, its internal contacts open or close to produce an electrical signal to the control system. This provides a discrete, positive indication of end-of-travel or a specific position, based on mechanical movement. In contrast, a proximity switch detects presence without contact using fields (magnetic, inductive, capacitive, etc.), so it doesn’t sense position via mechanical interaction. A pressure switch responds to fluid pressure, not the location of a machine part. A photoelectric switch uses light to detect presence or edges, also without relying on mechanical movement of the machine member to generate a position signal.