Switches Technical Information
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Basics of... Switches 
Terms
Pole: Number of sets of switch contacts.
Throw: Number of conducting positions, known as single or double.
Momentary: Temporary contact switch, goes back to rest position when released.
Open: Switch is not conducting.
Closed: Switch is conducting.
Pole & Throw Classifications
Single Pole, Single Throw (SPST): An on-off switch. A simple switch with one set of poles and one throw.
Single Pole, Double Throw (SPDT): This switch can be wired on-off or on in both positions and can power on two different circuits (A or B) in example.
Double Pole, Single Throw (DPST): A pair of single SPST on-off switches which work together.
Double Pole, Double Throw (DPDT): A pair of SPDT switches which work together.
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