What are the differences between SPST, SPDT, DPST, and DPDT switches?
Date: 02/12/2025
It’s important to note that these classifications do not define the number of positions a switch may have, nor whether it is momentary or maintained. A switch of any type can be designed as a single- or multi-position switch, and can operate in a momentary or latching mode depending on the application.
WHAT IS AN SPST SWITCH?
SPST (Single Pole Single Throw) switches are the simplest type of switch. They feature one pole and one throw, meaning they simply open or close a single circuit. SPST switches are ideal for basic on/off control.
Key features of SPST switches:
One pole, one throw: simple on/off function.
Wiring: extremely straightforward with just 2 terminals.
Applications: lighting, basic motor control, alarms, or any circuit where a single connection needs to be made or broken.
APEM SPST switches:
WHAT IS AN SPDT SWITCH?
SPDT (Single Pole Double Throw) switches are among the simplest and most commonly used types of switches. They feature one pole and two throws, allowing you to connect a single input to one of two output terminals. SPDT switches are typically used for simple on/off control (just like a SPST) or toggling between two circuits. In addition, they can be used to monitor the activation of a function, since activating the switch causes one contact to open while the other closes.
Key features of SPDT switches:
One pole, two throws: simple switching between two circuits.
Wiring: easy to wire with just 3 terminals.
Applications: ideal for basic controls in control panels, lights, motors, and alarms. can also be used to monitor the activation of a function.
APEM SPDT switches:
WHAT IS A DPST SWITCH?
DPST (Double Pole Single Throw) switches are the double pole version of SPST switches, with two poles and one throw per pole. This means you can control two circuits simultaneously, but without the flexibility of switching between multiple states. It allows already your system to have redundant output with twice the same information for increased safety. DPST switches are commonly used in simple systems where dual control is needed but multiple options aren’t required.
Key features of DPST switches:
Two poles, one throw: ideal for simple dual-circuit control.
Wiring: simple, with only 4 terminals.
Applications: common in systems that need to control two circuits at once without requiring multiple switching options (e.g., power source control).
APEM DPST switches:
WHAT IS A DPDT SWITCH?
DPDT (Double Pole Double Throw) switches are more advanced versions of the SPDT switch, with two separate poles, each able to connect to one of two output terminals. This allows the control of two independent circuits simultaneously or use the 2 circuits for redundancy.
DPDT switches are often used in systems where the operator needs to switch between two different power sources or control two separate devices with one switch.
Key features of DPDT switches:
Two poles, four throws: controls two circuits at once.
Wiring: more complex wiring with 6 terminals.
Applications: often used in motor control, power source switching, and machinery systems that require independent control of two circuits.
APEM DPDT switches:
SPDT VS DPDT VS DPST: A QUICK COMPARISON
Here’s a side-by-side comparison to quickly highlight the main differences between SPST, SPDT, DPDT, and DPST switches.
SPST (Single Pole Single Throw) | SPDT (Single Pole Double Throw) | DPST (Double Pole Single Throw) | DPDT (Double Pole Double Throw) | |
Poles | 1 pole | 1 pole | 2 poles | 2 poles |
Throws | 1 throw | 2 throws | 2 throws | 4 throws |
Wiring complexity | Very simple (2 terminals) | Simple (3 terminals) | Simple (4 terminals) | Complex (6 terminals) |
Typical applications | Basic on/off, lights, alarms | Control panels, lights, motors | Motor control, power source switching | Motor direction, power switching |
Switch types | Toggle, rocker, push button | Toggle, rocker, slide, push button | Toggle, rocker, push button | Toggle, rocker, slide, push button |
Price | Very affordable | Affordable | More expensive due to complexity | More expensive due to complexity |
Schematics
SPST
SPDT
DPST
DPDT
HOW TO CHOOSE BETWEEN SPST, SPDT, DPST, OR DPDT SWITCHES
Selecting the right switch depends on the complexity of your system and what you need to control:
SPST switches are perfect for the simplest tasks—just turning a single circuit on or off.
SPDT switches let you toggle between two circuits, making them ideal for slightly more advanced applications.
DPST switches control two circuits simultaneously without the complexity of multiple throws—great for
simple dual-circuit systems.
DPDT switches handle two circuits at once with multiple switching options, making them suitable for complex tasks like reversing motor direction or switching multiple power sources.
NEED HELP CHOOSING THE RIGHT SWITCH?
If you’re unsure whether an SPST, SPDT, DPST, or DPDT switch is best for your project, APEM’s experts are ready to help. Our team can guide you through the selection process to find the best switch for your specific needs.
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