In the fields of access control is the selective restriction of access to a place or other resource. The act of accessing may mean consuming, entering, or using. Permission to access a resource is called authorization. Locks and login credentials are two analogous mechanisms of access control.
Alarmed exit devices are for unlocking a door and souning alarm during emergency conditions people of an emergency panic device, or a push bar . The mechanism consists of a spring-loaded metal bar fixed horizontally to the inside of an outward-opening door. When the lever is either pushed or depressed, it activates a mechanism which unlatches the door allowing occupants to leave quickly from the building.