SPST, SPDT, DPST, and DPDT Explained - Littelfuse What do SPST, SPDT, DPST, and DPDT mean? SP and DP refer to single pole and double pole, ST and DT refer to single throw and double throw. Pole refers to the number of circuits controlled by the switch: SP switches control only one electrical circuit. DP switches control two independent circuits (and act like two identical switches that are mechanically linked). What is a Single Pole Double Throw (SPDT) Switch For example, a SPDT switch can connect to create a Ready Mode and a Standby Mode in a printer. Single Pole Double Throw (SPDT) Switch Circuit. Below is an example of a circuit which utilizes a single pole double throw switch. You can see above how a SPDT can be wired up to put a circuit in either one of two modes. When the switch is connected Spdt toggle Switch Wiring Diagram | Free Wiring Diagram Variety of spdt toggle switch wiring diagram. A wiring diagram is a streamlined standard photographic depiction of an electrical circuit. It shows the elements of the circuit as simplified forms, and also the power and also signal links between the tools.