Access control system having centralized/distributed control
Patent 4839640 Issued on June 13, 1989. Estimated Expiration Date: 
March 17, 2008. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
March 17, 2008. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent ReferencesStatistical multiplexing system for computer communications Self-contained programmable terminal for security systems Communication system with slot time error detection Patent #: 4570257 InventorsAssigneeApplicationNo. 07/171154 filed on 03/17/1988US Classes:340/5.33, Including link to remote indicator235/382, Permitting access340/3.51, Polling or roll call340/5.28, Timed access blocking340/5.5Input from central location for plural controlled devicesExaminersPrimary: Griffin, Robert L.Assistant: Smith, Leonard E. Attorney, Agent or FirmInternational ClassG07C 9/00 (20060101)AbstractThe 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.Other References
| |
