Here's a link to see what they look like
(Only the switch is OPEN with the magnet
engaged).
http://cgi.ebay.com/Lot-3-spst-magnetic- contact-switch-49-495-archer-
NIB_W0QQitemZ6025121124QQcategoryZ41969QQssP
ageNameZWDVWQQrdZ1QQcmdZViewItem
The one I used was a N.O./N.C. with a
common pole so it could be used either
way. At first I used the wrong type and I
had to use a constantly running computer to
reverse the switch sensing via software.
The powerflash module triggers with a
switch contact or applied voltage. Perfect
for use with the magnetic switch as it
provide that switch contact when the magnet
moves away from the switch. I don't think
it would interfer with your alarm setup as
the module has house and unit code 'wheels'
on it so you can set it to what you want to
match the chime or lamp modules.