On Thu, 29 Apr 2010 16:49:51 -0400, "RBM" wrote:


"Bitzer" wrote in message
...
I'm replacing a broken surface mount magnetic switch mounted on my garage
door that controls a signal light in the house that comes on when the door
is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?

As an electrician, I've been through this numerous times over the years. It
clearly depend on who you are talking to, and what trade they're in. IMO,
the "normal" position is the state the switch is in when nothing affects it.
Alarm people have the opposite take on it. My solution is to always buy
devices that come in the "form C" which is both open and closed circuits,
this way you can't go wrong


Yeah, then you can put one wire on the "common" and flip a coin.

Wire it NO and if the light goes off when it should come on then wire
it NC.

My best guess is that you should wire it NO and the magnet will close
the switch.