Switches are used to control the flow of electrical current. Either fully allowing or fully cutting off the flow of electricity. A switch works like a valve that is always either fully open or fully closed. There are many switch arrangements, some of which are shown below.

The simplest switch is the Single Pole Single Throw (SPST) switch. This switch is often used as an "On/Off" switch. It controls the current flow in a single circuit. The Single Pole Double Throw (SPDT) switch can control current from, or to, either of two circuits. Sometimes a double throw switch is referred to as an "On/On" switch. Some double throw switches have a center position where there is no connection to either circuit. This is sometimes referred to as a "center-off" or an "On/Off/On" switch.

Double pole switches are essentially two single pole switches that work in unison. These are used where two circuits need to be controlled simultaneously. The dashed lines shown with the double pole switches indicate that the switches work together.

Some switches are spring-loaded and return to the original position when released (either "on" or "off", depending on the switch and how it is used). These are called momentary-contact switches.

Basic Switch Types


Single Pole Single Throw (SPST)


Single Pole Double Throw (SPDT)
Rotary Switch
Rotary Switch


Double Pole Single Throw (DPST)
Double Pole Double Throw (DPDT)
Normally-open Pushbutton Switch

Normally-closed Pushbutton Switch
Open Switch
Closed Switch

Styles of Switches
Styles of switches

Top row: circuit breaker, mercury switch, rotary switch, dip switch (slide type), surface mount switch, magnetic reed switch; Bottom row: wall switch, bat handle toggle switch, inline switch, pushbutton switch, rocker switch, microswitch.

Ganging switches (and other devices)

Notice that the double pole switches above are essentially two switches connected by dashed lines. This means that the two switches work off one handle or knob. This is called ganging and is also used for other devices that need to work in unison. Ganged devices may be widely separated on a schematic diagram but will be connected by a dashed line.