Access Control System refers to exerting control over who can interact with a resource. Often but not always, Access Control System involves an authority, who does the controlling. The resource can be a given building, group of buildings, or computer-based information system. Access control is, in reality, an everyday phenomenon. A lock on a door is essentially a form of control. When a credential is presented to a reader, the reader sends the credential’;s information, usually a number, to a control panel, a highly reliable processor.
The control panel compares the credential’;s number to an access control list, grants or denies the presented request, and sends a transaction log to a database. When access is denied based on the access control list, the door remains locked. If there is a match between the credential and the access control list, the control panel operates a relay that in turn unlocks the door.