I purchased some 3-terminal switches online, but when I received them, they didn't work for me. I need the normally-closed function, and when I put my ohm meter across the normally closed terminals... nothing. When I put the magnet close... nothing. The normally open circuit seems to work fine--N/O until the magnet comes close, then closed. I sent the switches back as defective.
It seems that the security world these days doesn't want much to do with N/C switches, and I understand why. And if I peruse switches on line, they are mostly N/O.
Unless I look at overhead door switches, and then I see that most of them are advertised as N/C. Are they N/C when the magnet is near? Or when the magnet is absent?
(Amazon.com product link shortened)36274503&sr=8-10&keywords=garage+door+magnetic+switch#customerReviews
I'm wondering if different folks are describing it differently. I thought that "normally" meant with no magnet near. Is that correct?
I even saw an overhead door switch advertised as NC/NO, but it only had two leads--how the hell could that be?
I don't want to buy more stuff and find out it won't work.