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Door Objects for Access Control
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The first versions of access control used early CPUs with several readers connected to multiplex communication boxes. As systems grew, the communications strategies became more complex, unwieldy, and slow. The industry moved to distributed processors that could make the access decisions promptly and subsequently transmit the history of the transactions back to the central systems. These distributed processors were set up to store card numbers, access criteria for the doors that are served by them, and some number of historical transactions. The history was added for the case where the communication line is lost to the central CPU (host computer) or if the system is using dial-up communication. Since all of the manufacturers call their distributed processors by different names, I will use the generic term Smart Remote Box (SRB) for these distributed processors.

Along with the complexity of the SRBs came the full interaction ofaccess control systems with alarms for the access controlled doors. An alarm contact on a card-in/free-exit door must be shunted for valid transactions.  When entering, a valid card read will shunt the alarm.  When exiting, various devices that will automatically detect a person that was exiting are used. These devices are typically called a REX, which stands for Request to Exit. The process of accurately determining when a door is secure, in transition, held open, or in a forced open state continues to be a challenge today.

Attempts at false alarm reduction continue to be made by theusers of large systems. Many large systems today have more false door forced alarms and too many door held alarms to allow the central monitoring area to function appropriately. There are only so many calls to which a given set of rovers can respond. And it is useless to spend the dollars for a rover to respond to a false signal from the system. There is a great economic need to clean up this part of the access control industry. There are enough differences in the various doors and hardware that are served by any manufacturer’s systems that all of the possible scenarios of operation have not been fully considered in the design. Thus, there is a need for operational change. Getting the manufacturers to make these changes is difficult because it is very expensive to do safely and correctly. The ramifications are great.

The microcode structure that defines the SRB actions at a particular door have historically been stored in Programmable Read Only Memory (PROM). To change the code in a PROM, the chip must be replaced, thus requiring physically visiting each SRB. In the last few years, FLASH memory has become available which allows the microcode program in the SRB to be downloaded from the host without the need to physically visit each SRB. With flash memory, the process of changing the operation of an SRB is much more efficient. Flash memory has made it possible to accomplish a door object based microcode download from the host computer.

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