SP means single pole, DP is double pole.
Back in the old days of power, they used to turn switches on and off wtih a
big wood pole. A "double pole" is sorta old speak for two circuits that can
turn on and off.
Single throw means one place you can connect the pole. Double throw is two
a double pole single throw thermostat allows you to turn both sides of the
filament on and off -- much safer than leaving it always energized.
A single pole thermostat would be OK on a 110 volt system.
Christopher A. Young
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