The ABCs of Security Alarm Signaling
Let’s examine the most prevalent types of alarm signaling systems, the pros and cons of each method, and discuss how they’re being applied.
Although the use of add-on digital dialers over POTS was an improvement over dedicated lines, it did not address the need for more detailed information (i.e. room, hallway, floor, or as is the case today, the exact device). Information is critical if first responders are to be effective. For example, because seconds count when there’s a fire, it’s important firefighters know where a fire began and where it has migrated to – all before they arrive on the scene.
In due time, the digital dialer migrated directly onto the alarm panel motherboard. This direct connection with the central processor enables the digital dialer to transmit zones and points to central station operators, which provides for a better informed response. This includes a variety of trouble codes, such as low battery, AC power failure, keypad tamper, missing device, failure to communicate and others.
In brief, the most utilized form of alarm signaling to this day involves the use of traditional telephone lines using POTS in conjunction with the public switched telephone network (PSTN).
“The primary reason is because POTS was such a ubiquitous form of person-to-person communication for so many years, that it simply takes a long time to go away,” says Dave Roberts, vice president of engineering for DMP. “Combine that with consumers already paying for this technology for their own use, and the alarm dealer could essentially use it for free to transport alarm signals. A free-to-use service that generates recurring monthly revenue is hard to give up for an alarm dealer.”
POTS is probably the most fault-tolerant signal transport method in existence where it comes to alarm signaling. Not only is it free to alarm dealers to use when it’s already in place, most telephone carriers are able to provide a dial tone more than 99% of the time. That is another reason the alarm industry has fought to keep it. It’s hard to replace free and reliable.
Why POTS Is Losing Ground
There are several disadvantages associated with POTS that give ample cause to consider a cellular or IP-related solution. The first is the relatively slow data transmission rates (bandwidth) experienced using POTS for sending alarm signals. The second is a general lack of mobile applications. The third is the speed in which POTS lines in homes are going away for a generation of people that opt for cellphones only.
For example, panels using POTS lines for communication typically do not communicate faster than 300bps, while today panels on cell or network communicate at broadband Internet speed. The greater the bandwidth, the better that data transmission rate and the faster response the client will realize. But wait, there’s more.
Metallic lines also are susceptible to an assortment of other problems worth noting. First, data sent along metallic phone lines can be corrupted or destroyed by electromagnetic (EM) sources, such as lightning, nearby high-voltage lines and sunspot activity. There’s also the possibility of deliberate sabotage, either on a local or catastrophic scale. Possible sources include the deliberate introduction of intense EM through an electromagnetic pulse (EMP) weapon. In addition, there could be someone armed with a pair of wire-cutters outside the premises (line-cut) or even a motor vehicle striking a nearby utility pole/pedestal.
Besides these issues, POTS is on the wane for two additional reasons. First, more and more households are switching exclusively to cellular or broadband VoIP. Second, POTS is gradually disappearing as telephone carriers work to retire their metallic cable infrastructure, replacing it with fiber or some other type of transmission media. Communication carriers are constantly working to convince the FCC that the public’s interest is best served by the development of an all-digital communication infrastructure. In fact, if AT&T had anything to do with it, obsolescence would have been declared long ago.
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About the Author
Al Colombo
Al Colombo is a long-time trade journalist and professional in the security and life-safety markets. His work includes more than 40 years in security and life-safety as an installer, salesman, service tech, trade journalist, project manager,and an operations manager. You can contact Colombo through TpromoCom, a consultancy agency based in Canton, Ohio, by emailing [email protected], call 330-956-9003, visit www.Tpromo.Com.
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