toggle switch

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Large toggle switch, depicted in circuit 'open' position, electrical contacts to left; background is 1/4" square graph paper

A toggle switch is a class of electrical switches that are actuated by a mechanical lever, handle, or rocking mechanism.

Toggle switches are available in many different styles and sizes, and are used in countless applications. Many are designed to provide, e.g., the simultaneous actuation of multiple sets of electrical contacts, or the control of large amounts of electric current or mains voltages.

The word "toggle" is a reference to a kind of mechanism or joint consisting of two arms, which are almost in line with each other, connected with an elbow-like pivot. In the phrase "toggle switch" it specifically refers to one kind of mechanism that can be used to implement a positive "snap-action." However, the word "toggle switch" has come to mean any kind of switch with a short handle and a positive snap-action, whether it actually contains a toggle mechanism or not.

Bank of toggle switches on a Data General Nova minicomputer front panel

In electronics, the word "toggle" has come to mean circuits that embody an electronic analog of a mechanical snap-action. That is, bistable switching circuits are sometimes called "toggles." In particular, the word can be used for a toggle flip-flop, a circuit in which an impulse causes a transition from whichever state to another state and it´s depends of the output Q. By further extension, in software, the act of switching from one to the other of two states can be called "toggling", as in "He toggled the switch, and the computer's lights blinked".

When used in computer programs, the term "toggle" is used to indicate turning a feature on, or off, typically by pressing one key to turn the feature on, and then pressing the same key again, to turn the feature off.

The advantages of such a switch are quite simple. The light is quite handy to turn on and off. But the disadvantages are that the lever which protrudes form the actual switch may become stiff and then harder to use.