The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 13, 1989
Filed:
Mar. 17, 1988
Richard Ozer, Brookline, MA (US);
Edward DeSantis, Boston, MA (US);
Brett Tomlinson, Brighton, MA (US);
ADT Inc., Parsippany, NJ (US);
Abstract
The access control system according to the present invention provides for the centralized control of the system operating parameters, including all times, access codes, alarms, error messages, and pass-coded indications. The access control system communicates with a plurality of remote card readers, at which point the user enters a code to gain entry into the protected areas. The access control system according to the present invention selectively stores limited information at each card reader location, wherein access control is still maintained, even if the central data system becomes inoperative. Moreover, the communication between the central data system and the plurality of card readers includes data transfers through a plurality of subsystems, each having a data processing program therein. The system according to the present invention provides for efficient communication between asynchronous operating subsystems through the controlled use of a first-in-first-out (FIFO) data register pair. In this manner, each subsystem according to the present invention operates independently until a data transfer is initiated, causing the other operations to be suspended to permit the transfer of data. The FIFO allows for data to be transferred at different rates between subsystems, allowing freedom in subsystem operation and data transfer rates.