69. ACCESS CONTROL SYSTEM OPERATION

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. The control panel also ignores a door open signal to prevent an alarm. Often the reader provides feedback, such as a flashing red LED for an access denied and a flashing green LED for an access granted.The above description illustrates a single factor transaction. Credentials can be passed around, thus subverting the access control list. For example, Alice has access rights to the server room but Bob does not.


Alice either gives Bob her credential or Bob takes it; he now has access to the server room. To prevent this, two-factor authentication can be used. In a two factor transaction.The presented credential and a second factor are needed for access to be granted. The second factor can be a PIN, a second credential, operator intervention, or a biometric input. Often the factors are characterized assomething you have, such as an access badge or passcard, something you know, e.g. a PIN, or something you are, typically a biometric input.


Agrigentum there is a single four-panel door carved in stone. In the Blundell collection is a bas-relief of a temple with double doors, each leaf with five panels. Among existing examples, the bronze doors in the church of SS. Cosmas and Damiano, in Rome, are important examples of Roman metal work of the best period; they are in two leaves, each with two panels, and are framed in bronze. Those of the Pantheon are similar in design, with narrow horizontal panels in addition, at the top, bottom and middle. Two other bronze doors of the Roman period are in the Lateran Basilica.