Q: The requirement that listed receivers must be used connected to central station computers seems archaic. Why can’t the central station computer process the signals directly?
A: This is a good question. The answer is found primarily in two documents: NFPA 72’s requirement that systems needs to be “listed for the application” and to UL 1981 that asks for alarm signals to be first processed by receivers and then fed to redundant computers.
UL 1981 prescribes that a central station’s computers are an adjunct to the front end receivers. As such these computers are not listed. The software, however, is “classified” by Underwriters Laboratories (UL). It is, therefore, checked for compatibility in its recommended hardware configuration. The hardware/software package, however, is not run through a full listing program.
A listed central station should be able to revert to processing alarms with only its receivers in a degraded mode using an offline data base. These procedures are required to be practiced periodically by the central station company.
While technically they can, central station monitoring software companies do not want to perform the DACT (i.e. “dialer”) receiver function because it requires specialized hardware and will some day become obsolete. Often receiver manufacturers design receivers to process alarms from their panels, especially when proprietary dialer formats are involved.
The future, however, is IP, using either intranet or the public Internet. Processing alarms in that mode is a natural function of modern software operating systems. Efforts are underway to standardize the IP protocol used in alarm panels. Fortunately, this is being done early in the evolution of IP to forestall the proliferation of proprietary DACT protocols.
Simplistically, there is no fundamental reason why central station computers cannot be listed as receivers today. These “receivers” would be “listed for the purpose” as receivers and would also accomplish the entire processing function. But the practicality is that this possible listing effort is arduous and expensive. Furthermore, when completed would yield platforms that are short lived. With the constant change and progress of computer technology, the ability to buy and install the same versions listed would be very difficult to achieve and probably not desired anyway.
With the use of front end receivers, a central station is able to “manually” process alarms in the event of a catastrophic failure of the central station computers. In a “receiver-interfaced-to-computer” world, this is a characteristic worth keeping.
However, a creative way to preserve this level of response availability can be accomplished in a strictly computer processing environment. In such an environment, two or more computers would have to be protected from failure mechanisms that will render them inoperative. Perhaps the only way this can be accomplished is with a tertiary computer or by geographically dispersed redundant processing.
Using the consensus process, the industry can define the “processing environment” required. The appropriate NFPA and UL committees should debate this issue with a view toward the IP future.
Louis T. Fiore is a consultant from Sparta, NJ. He is Past President of CSAA (1997-1999) and President of L.T. Fiore, Inc. His practice includes the use of wireless and the Internet for alarm monitoring, as well as regulatory issues for security systems in general. He also serves as Chairman of Central Station Alarm Association’s (CSAA) Alarm Industry Communications Committee (AICC) and Standards Committee. He is the current chairman of the SIA’s Security Industry Standards Council (SISC) and a long-time member of the Supervising Station Committee of NFPA 72. Send your questions to [email protected].
