What distinguishes a selector switch?

A selector switch is specifically designed to allow the user to choose between different circuit paths or functions within a circuit. This versatility is essential in various electrical applications, as it enables operators to control which circuit is active at any given time. By using a selector switch, one can route power or signals to different components or systems based on the selected position of the switch.

The other options presented do not accurately capture the primary function of a selector switch. While some switches may indeed turn on one circuit or serve other specific purposes, such as changing voltage levels or acting as an emergency shutoff, these characteristics do not define what makes a selector switch unique. Instead, it is the ability to select from multiple circuit paths that sets it apart and makes it a valuable component in many electrical systems.