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New fire alarm communication technologies
by Art Black
There is a quote from the Silicon Valley establishment that technology doubles every 18 months. The quote actually refers to computers, but from a fire alarm viewpoint, it applies equally to the transmission technologies of the quickly evolving communications revolution.
Today, home and business telephone service is being provided not only by the regulated regional Bell operating companies but by new, nontraditional, unregulated providers such as the cable industry, broadband carriers (VoIP), and others. Because these nontraditional providers attempt to emulate the phone company for voice service, many people assume that these technologies can use digital alarm communications systems (DACS) “just like the phone company.” This is incorrect.
In fact, the question of using DACS is complicated and seems to be getting more complex, particularly with regard to the requirements of NFPA 72, National Fire Alarm Code ®.
To understand NFPA 72’s requirements for DACS, a little history is needed. In the past, when a new transmission technology was developed, the concept was brought to the appropriate technical committee, and, with the technical committee’s consensus, the requirements for that particular technology were put into the standard. With the technology recognized by the standard, the next step was getting it tested and listed by Underwriters Laboratories and marketing it.
A quick read of Chapter 8 of the 2007 edition of NFPA 72 show that, at various times in the past, a number of specific technologies, such as active and directly connected non-coded signaling, were recognized in the code. In the 1980s, a “new” invention called digital alarm communications systems was developed, using regular seven-digit loop-start telephone lines. Since these devices used passive communications and one could never be sure whether the phone lines were active, the committee rejected the technology. Only on the third attempt did the committee agree to put DACS into the standard, and only then with some safeguards to protect against the inherent unreliability of the public switched telephone network.
Those safeguards included the redundancy that is still in the standard. Digital alarm communications transmitters ( DACTs ) and digital alarm communications receivers ( DACRs ) had to be connected from a protected premises to a copper, POTS, loop-start telephone line, provided by the phone company. A DACT may only be connected to a copper connection POTS telephone line going to a regulated phone company central office. That is STILL the requirement for DACTs and DACRs, and nontraditional providers need to adhere to the requirement if they are to comply with the NFPA 72.
How do cable “phones,” internet “phones,” or other non-traditional communications methods meet the minimum requirements of NFPA 72?
For the 1999 edition of the code, the Supervising Stations Technical Committee decided to write a generic performance-based section to deal with emerging technologies in lieu of putting additional specific technologies into the code. In the 2007 edition, these requirements are found in Section 8.6.4, Other Technologies.
The cable and VoIP industries need to configure their products to meet the requirements of Section 8.6.4.
Most of the requirements of this section are easily met, although two subsections will present technical challenges to the VoIP and cable industries: emulation of a loop-start telephone, and provision of a minimum of 24 hours of standby power for the premises portion of the communications link.
The cable and VoIP industries need to focus on getting their products listed under Section 8.6.4 and not believe their own advertising. When it comes to DACS, the new phones are not “just like your old phone, only less expensive!”
Art Black is the chair of NFPA 72 Supervising Station Technical Committee, which is the responsible technical committee for DACS. The views of the author are not to be considered formal interpretations of NFPA 72.
The Building Fire Safety Systems Section shall be open to those NFPA members professionally involved in design, approval, manufacture, distribution, installation, maintenance, and certification of alarm, detection, suppression, security, and smoke control systems. The section shall also be open to users, owners, and those responsible for training on such systems. The purpose of the section shall be as follows:
In this Section: