Which term describes a switch with one input and one output contact?

• A. An on/off switch that allows current to flow when closed
• B. A two-way switch
• C. A switch with one input and one output contact
• D. A normally closed contact

Answer: (C)

A switch that controls a single circuit path uses one movable contact (pole) that connects to one fixed contact (throw). This setup is called a single-pole switch (SPST). It describes exactly one input and one output contact, which is why it’s the best fit here. An SPST can be normally open or normally closed, meaning the circuit either opens or closes when the switch is actuated, but the essential idea is the single path between input and output.

The other descriptions point to different configurations: a two-way switch implies more than one path or position to switch to, a normally closed contact describes the default state rather than the contact count, and an on/off description focuses on function rather than the number of contacts.