Switch function (ON) = return spring
Pole types:
SPST = single pole and single throw
SPDT = single pole double throw
DPST = double pole and single throw
DPDT = double pole 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 as two identical switches that are mechanically connected).
“Throw” refers to the outer position of the actuator: ST switches close a circuit in only one position. The other position of the handle is off. DT switches close a circuit in the Up position, as well as the Down position (On-On). A DT switch can also have a middle position (often On-Off-On).
