Difference between Single Pole Switch and Double Pole Switch

Updated on June 28, 2018

A switch is a device that is used to control current flow in an electrical circuit. A simple switch provides electrical connection between two terminals when a conductor connected to one terminal is brought into contact with another terminal. There are two types of pole switches, namely: the single pole and the double pole switch. We’ll tell you more about these switches and their differences in this article.

Summary Table

Single Pole Switch Double Pole Switch
Has two terminals for SPST (single pole, single throw) or three for SPDT (single pole, double throw)Has four terminals for DPST (double pole, single throw) or six for DPDT (double pole, double throw)
Controls a single circuitCapable of controlling two circuits simultaneously

Definitions

single pole switch
A single pole, single throw (SPST) knife switch

A single pole switch usually refers to a single pole, single throw switch (SPST). It is a switch that provides a simple connect or disconnect capability across two terminals. It is commonly used for on/off applications such as light switches.

double pole switch
A double pole, double throw (DPDT) knife switch

A double pole switch may refer to a double pole, single throw switch (DPST). It is simply the combination of two SPST switches simultaneously controlled by a single mechanism.

Single Pole Switch vs Double Pole Switch

The main difference between a single pole switch and a double pole switch is related to the number of terminals they have and the number of circuits they control. A switch is said to be “open” when there is no current flow between two terminals and is “closed” when the current flows from one terminal to the other. A common application of a switch is to turn the room lights on or off.

A single pole switch can either be an SPST (single pole, single throw) switch or an SPDT (single pole, double throw) switch. An SPST is a switch that has two terminals, while an SPDT has three terminals. It is a switch that toggles connection between one common terminal to either of two other terminals.

A double pole switch, on the other hand, is essentially a switch that allows or disallows current flow between two distinct lines or circuits at the same time. It can either be a DPST (double pole, single throw) switch or a DPDT (double pole, double throw) switch. A DPST has 4 terminals, while a DPDT has 6 terminals. This is essentially two SPDT switches that are controlled by a single mechanism.

Single pole switches control only a single circuit whereas double pole switches are capable of controlling two circuits simultaneously.

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