By Shawn Welsh
What New Code Changes Mean for Sole-Path Cellular
Among the many improvements found in the latest edition of the National Fire Alarm and Signaling Code (NFPA 72- 2010), one should be of particular interest to fire-system Integrators: cellular technology is now permitted as a sole means for alarm communications. This welcome change allows the integrator to earn revenue from the alarm system's communications path without burdening the customer with the expenses and inconveniences of a landline.
Of course, change always brings with it some opposition and that means Integrators must educate Authorities Having Jurisdiction (AHJ) on the aspects that most directly affect their businesses.
Recently, I wrote an article entitled, “Cellular as a sole communications path for fire.” It explains how using cellular as a sole communications path benefits both the end customer and Integrator Although the market offers just a few UL 864-listed products—such as Telguard's TG-7FS—savvy dealers are already leveraging this code change.
What integrators are saying
"The benefit of cellular as the sole path is huge for the industry as a whole," said Alan Foreman, the operations manager of Washington Alarm in Seattle. "To the end user customer, it's transparent and it works like it's supposed to. They also like the cost savings from not having to install a backup line or landline. For us, the dealer, it's affordable and can be installed quickly."
You’ll hear such praise from integrators everywhere: sole-path cellular indisputably helps the bottom line. As you can imagine, the challenge isn't in persuading customers to adopt—they do so readily because of savings and convenience. Rather, the challenge is in gaining regulatory approval.
Most often, resistance on the part of AHJs falls into three categories: awareness, applicability and reliability. Awareness and applicability are closely linked. Even if a jurisdiction is already using NFPA 72 2010, the sheer number of changes from the 2002 edition means that the sole-path allowance clause, which is hidden in the appendix under general communications, can easily be overlooked. As such, integrators must understand the code well enough to help an AHJ locate and correctly interpret the sole-path clause. Just such a “code walkthrough” can be found in the sidebar or downloaded from SD&I's website at ________________.
For jurisdictions still operating under the 2002 edition, cellular is mentioned only as a suitable secondary path for a DACT. ButiIntegrators in these jurisdictions shouldn't give up hope. The 2002 edition clearly allows the concept of Equivalency (Section 1.5) and under Equivalency Cellular can be approved as a sole path. This is the case because cellular is deemed equal to DACT and private radio by its inclusion in the newer and more recently vetted 2010 edition.
However, even if an informed and prepared integrator convinces the AHJ of cellular's applicability, he or she still must defend its reliability. Questioning the reliability of the cellular network generally means questioning the durability of the hardware (e.g., towers), the robustness of the software (e.g., message transmission) and the presence of an adequate backup path.
Cellular path redundancy
The usual suspect is the cell tower. Many people assume a cellular device communicates with only one cell tower and that the tower represents a potential point of failure. This is not true. Just like a point-to-multipoint mesh-networking product, a cellular device can also communicate with multiple towers offering path redundancy. In the rare case that the primary tower is taken down for any reason, communications are immediately resumed through the next visible tower. The challenge is proving that multiple cell towers are actually in range of the installed location. To this end, some manufacturers can indicate that multiple towers are visible through their equipment's LEDs, which should ease the AHJ's concerns on an installation-by-installation basis.
Even though the cell tower often comes to mind during a cellular outage, subsections of a cell network can also experience temporary service outages. The GPRS network is actually an overlay network that operates on top of the GSM network. The former delivers IP data, while the latter delivers voice and SMS. But if the GSM network is down then everything is down: IP data, voice and SMS. This is rare because voice is the carrier's main source of revenue and, as such, is engineered for redundancy. In fact, even the U.S. Government tracks outages based only on voice minutes lost; it doesn't pay any attention to data outages. As a result, brief data outages are not a critical issue.
Because the GPRS network is a subset of the GSM network, IP traffic can suffer an outage while voice and SMS traffic still flow as usual. This is not a condition that many people would notice, but in the case of sole-path fire communications the line must be supervised every five minutes, which means even a brief outage would be detected. If this occurs, regulations stipulate that the site personnel and central station must be notified. For systems relying exclusively on GPRS, these brief but periodic outages will frustrate the customer and tarnish an Integrator's reputation, which is why some equipment manufacturers always include SMS as either the primary or backup communications method. With SMS backup, even if the GPRS network fails the fire-communications protection remains intact and no one needs to be notified. This is another point to stress with an AHJ to demonstrate the resiliency of cellular as the sole-path.
Like many prior technologies, cellular must overcome resistance based on awareness, applicability and reliability. However, as with earlier code improvements, AHJs will gradually warm to the idea of cellular as the sole path for communications. With code knowledge and the proper equipment, savvy integrators can calm the AHJ’s safety concerns and, for those efforts, watch as their RMR and customers’ sense of appreciation grow.
“The sole-path allowance clause is hidden in the appendix under general communications.”
“The challenge today is in gaining regulatory approval from the AHJ.”
Shawn Welsh is vice president of marketing and business development for Telular Corporation, Atlanta.