Normally open (NO) contacts mean that current does not flow through them in its normal state. You open a panel or access box, see. Normally open (NO) and normally closed (NC) are two different terms that are used extensively in the world of electrical components, electronics, and engineering. The problem is what is normal? A standard wired alarm door contact is, in its uninstalled state, open. However, when installed in a door jam with a magnet on. In electrical systems, NO and NC stand for Normally Open and Normally Closed, respectively. The switchable type is a SPDT (Single Pole Double Throw) type, and can be switched from NC to NO or NO to NC.