SPDT means single pole double throw. It switches current either to one circuit, or a second circuit. An ordinary contact is single pole single throw, (on/off).


00 SPDT switch in position B


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single poll double throw

one common with either a closed contact or a open contact


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Rocky_T_Squirrel, Esq.

Hi, What does "SPDT" refer to? Sentrol makes a magnet switch with no "SPDT" I can't figure it out. Steven

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can't figure it

Google is your friend....

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Just in case you run into them, the same reference it made to relays too.

SPST Single pole single throw SPDT Single pole double throw DPST Double pole single throw DPDT Double pole double throw.

and obviously three pole. Four pole, etc .

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Years past these were also referred to as Type "C" contacts used especially in Direct Wire systems to cause a "Double Drop" (open and short to ground) when the device was tripped. This needed a 4 wire loop or a correctly wired 2 wire circuit with end of line resistors installed.

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Electrical Parlance for "Single Pole- Double Throw" as in a switch.

Steven wrote:

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Mike Sokoly

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