The ADD5110 provides an interface between a card reader and the advanced central controller (AC5102 or AC5200) for up to two card readers. When a cardholder presents the access card at an entry or exit reader the ADD5110 reader interface interprets the encoded information and sends this data to the controller. The controller then checks the validity of the cardholder‚ and if the appropriate permissions have been assigned‚ the controller sends a message back to the reader interface allowing it to unlock the door and provide passage. It can also report the status of the door (locked or unlocked) at any time.