It's like Carl Boyd said but another way to look at it is that when the
output is ON, PNP will give you +12V out (when used with a 12V supply) and
NPN will give you 0V out.

RogerN

"Karl Townsend" wrote in message
anews.com...
I'm about to purchase a photo eye. http://tinyurl.com/6bjmeb

What's the difference between PNP and NPN? I just want an eye that's NC
powered by 12VDC that uses very little power.


Karl