Honeywell 947 Frequently Asked Questions

What Do Normally Closed and Normally Open Mean?
"Normal" is the normal state of an opening, such as a door. Normally open/closed refers to the state of a contact connected to a door in its normal position.
Added:

When Would I Need a Honeywell Steel Door Contact?
Steel doors present problems for traditional door/window sensors. A steel door magnet, which is a bit stronger can solve the problem.
Added: