What is SPDT Switch? its features, working & applications

SPDT stands for Single Pole Double Throw, a switch that consists of three terminals and connects the source terminal and one of two output terminals.An SPDT switch allows for an “ON/ON” configuration, which means the switch’s input terminal is always completing one of the two possible circuits that the switch controls.

  • If the switch is in the “ON-1” position, the connection between the input terminal is established with the first output terminal, thus completing the first circuit.
  • If the switch is set to “ON-2,” the second output terminal establishes the connection with the input terminal, thus completing the second circuit.

Features of SPDT Switch

  • It has three terminals: common, normally open (NO), and normally closed (NC)
  • The common terminal is connected to either the NO or NC terminal depending on the switch position
  • It can be actuated manually or by a mechanical or electrical signal
  • It can handle moderate to high current and voltage ratings, depending on the specific model

Working of SPDT Switch

  • In its default position, the common terminal is connected to the NC terminal
  • When the switch is actuated, the common terminal is connected to the NO terminal instead
  • This action can be used to switch between two different circuits or to control the direction of current flow in a circuit
  • The switch can be spring-loaded so that it returns to its default position when the actuating force is removed

Advantages of SPDT Switch:

  • It is less cost
  • It is reliable for most the applications
  • It can work with high voltages & currents.
  • High switching currents let the device control relays, pumps & drive motors.


  • Switching between two power sources
  • Controlling the direction of current flow in a motor or other electromechanical device
  • Selecting between two different signal sources in a circuit
  • Circuit protection and safety, such as shutting off power to a device in case of a fault or overload.

Overall, SPDT switches are versatile components that can be used in a wide range of electrical and electronic applications.

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