<P> The moving part that applies the operating force to the contacts is called the actuator, and may be a toggle or dolly, a rocker, a push - button or any type of mechanical linkage (see photo). </P> <P> A switch normally maintains its set position once operated . A biased switch contains a mechanism that springs it into another position when released by an operator . The momentary push - button switch is a type of biased switch . The most common type is a "push - to - make" (or normally - open or NO) switch, which makes contact when the button is pressed and breaks when the button is released . Each key of a computer keyboard, for example, is a normally - open "push - to - make" switch . A "push - to - break" (or normally - closed or NC) switch, on the other hand, breaks contact when the button is pressed and makes contact when it is released . An example of a push - to - break switch is a button used to release a door held closed by an electromagnet . The interior lamp of a household refrigerator is controlled by a switch that is held open when the door is closed . </P> <P> A rotary switch operates with a twisting motion of the operating handle with at least two positions . One or more positions of the switch may be momentary (biased with a spring), requiring the operator to hold the switch in the position . Other positions may have a detent to hold the position when released . A rotary switch may have multiple levels or "decks" in order to allow it to control multiple circuits . </P> <P> One form of rotary switch consists of a spindle or "rotor" that has a contact arm or "spoke" which projects from its surface like a cam . It has an array of terminals, arranged in a circle around the rotor, each of which serves as a contact for the "spoke" through which any one of a number of different electrical circuits can be connected to the rotor . The switch is layered to allow the use of multiple poles, each layer is equivalent to one pole . Usually such a switch has a detent mechanism so it "clicks" from one active position to another rather than stalls in an intermediate position . Thus a rotary switch provides greater pole and throw capabilities than simpler switches do . </P>

What type of switch is a computer power button