Toggle switches are mechanical devices that make or break electrical connections in a circuit by the closing or opening electrical contacts when the protruding actuator is manually moved (toggled) from one position (throw) to another. Toggle switches are defined by their number of poles and throws. Pole refers to the number of separate circuits that the switch controls. A single-pole, single throw switch controls just one circuit as in a simple on/off switch that connects or disconnects two terminals. Changeover contacts are double throw.