Abstract: A device for use with security systems for residential or commercial buildings is disclosed which prevents an entrance door to the building both from being locked without first activating the security system, and from being unlocked without first deactivating the security system. The system uses an electromechanical interlock to prevent a deadbolt from being moved from an unlocked position to a locked position until the security system is armed. The eletromechanical interlock also prevents the deadbolt from being moved from the locked position to the unlocked position until the security system is disarmed.