NPN stands for negative, positive, negative. It is also known as sinking.
PNP stands for positive, negative, positive. It is also known as sourcing.
The NPN (negative, positive, negative also known as sinking) and PNP lines are used to signal the light to turn on or off. The NPN line requires a signal of ground potential, typically less than 1VDC to activate. The PNP line requires a signal between +4VDC and +24VDC to activate. If the light is being used in continuous operation either the NPN can be tied to ground or the PNP can be tied to +24VDC. For a light to function properly, apply either an NPN or PNP signal, not both.
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