What Is a Toggle Switch?

A toggle switch is a mechanism that does one of only two things: "On" and "Off." The familiar bat-handle switch might provide power to a piece of farm equipment, or nestle among many switches and dials on an airplane control panel. Other examples are the familiar up/down handle of a light switch, and the fancier button that turns on your stereo. Some circuit breakers operate by way of a toggle switch.

Definition

The noun "toggle" refers to a pin or knob that keeps something fastened, with applications in the nautical, fashion and carpentry worlds. A knot with a toggle will not untie, and put a ship at danger. A toggle is what a car coat wearer expects to button up. A bolt with a movable crosspiece at the end holds fast in the wall.
The intransitive verb "toggle" means to switch between two options, which brings our discussion to the word "switch." Relevant meanings for the noun "switch" include "a shift or change" and "a device that shifts or changes something."
It follows, then, that a toggle switch refers to a mechanism that changes status. An electric toggle switch is a spring-loaded mechanical device that opens or closes an electric circuit when toggled, or manually moved. Depending upon its position, the switch completes or interrupts the flow of electricity.

History

Joseph Swan demonstrated his new invention, the incandescent lamp, in 1878, and Thomas Edison, his similar invention within the year. What was needed was an effective on/off device. Englishman John Holmes invented the first quick-break light switch in 1884. In 1898, Newcastle-upon-Tyne in northeastern England became the first electricity-lighted city, thanks in part to the toggle switch.

Electric Toggle Switches

Electric toggle switches may be single-pole or double-pole, may handle various current loads, and may connect one or more terminals when switched.
A Single Pole-Single Throw (SPST) switch opens or closes one circuit between two terminals. A Single Pole-Double Throw (SPDT) switch connects one terminal to either of two terminals (three-terminals in all). A Double Pole-Single Throw (DPST) switch has four terminals that connect or disconnect two pairs of terminals simultaneously, and a Double Pole-Double Throw (DPDT) switch (six terminals) connects one pair of terminals to either of two other terminal pairs.

Uses for Physical Toggle Switches

A building contains many light switches; any that simply turn a light on or off, as opposed to dimming it, probably is some form of toggle switch. Appliances and other sorts of machinery usually have a Power On/Power Off---a toggle switch. Some circuit breakers fall into the toggle switch category. Complicated machinery from lift trucks to airplanes have one or more banks of toggle switches. Musicians use mixing boards, with multiple input and output channels, each of which is actuated by a toggle switch. The applications are legion in a variety of industries, including industrial controls, marine panels, ground transportation, marine transportation and agriculture.

Software Toggle Switches

Think beyond the mechanical, and you have a software toggle, which may refer to several options, not just two. A software toggle can allow switching among many choices--windows on your computer screen, for instance. Press a certain key (or combination of keys) once, and you move from Choice 1 to Choice 2. Press it again, and you go on to Choice 3. After you navigate all choices, the next keypress returns you to Choice 1.
A software toggle switch is a section of computer code that includes an array of choices, only one of which may be true at a time. One example is a checkbox list in which only one option may be activated. You may order either a fish or vegetarian or chicken luncheon at the convention for which you are registering online. If you click "vegetarian," and try to add "chicken" with another click, the software toggle switch disconnects "vegetarian," as you click "chicken."

Resources

• Blue Sky switches
• Boat controls
• Surplus Sales of Nebraska switches