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Toggle Switches

Toggle switches are among the most basic and most common of all electronic components, the switch moves contacts that either provide a path for current to flow through or moves those contacts in such a way that the path is cut. The toggle switches most people will be familiar with are light switches. You can learn more in our complete guide to toggle switches.

How Does a Toggle Switch Function?

Toggle switches may vary a bit in function from one to the next depending upon their configurations. However, the basics are the same.

When the actuator (the toggle itself) is moved, the armature in the switch moves the contact into position either energizing the circuit or de-energizing it. Once the switch is moved from one position to the other, it typically stays that way. There are also momentary switches, which energize or de-energize a circuit for as long as they are actuated and then go back to their normal state once the actuator is released. This is accomplished via a spring mechanism that exerts a force on the armature from the inside.

Contact Configuration of a Toggle Switch

  • A single pole single throw (SPST) switch is the simplest and most common type of toggle switch. These switches allow simple on and off operation for a single circuit. Most light switches are SPST switches.
  • Single pole double throw (SPDT) switches can be used to change where a voltage is directed. The double throw means that the switch can be used to energize two different circuits - one at a time - from a single source of energy.
  • Double pole single throw (DPST) switches allow an operation that is very similar to having two SPST switches hooked together in one device. The switch can turn two circuits on and off. These are very convenient when more than one device needs to be controlled with the same switch.
  • Double pole double throw (DPDT) switches allow two different circuits to be served by the same pole. These are used in applications where a circuit may need to have changing voltages applied to connected devices.

There are also switches with the designation CO, such as SPCO (single pole changeover) switches. These have an off position in the middle of the switch and can be used to energize or de-energize two different circuits attached to the device.