Current trends in fire alarm communication technologies

As POTS becomes more rare, companies turn to IP and GSM connections


The monitoring of fire alarm communications via phone lines has been the industry standard since the mid-1980s. Although telecommunications technologies have improved significantly with the evolution of the Internet, the quality of fire alarm communications has steadily declined in recent years. Following telecommunications' lead, it appears the fire industry could also seek benefit from the World Wide Web.

Calling Complications

The PSTN (public switched telephone network) was originally a network of fixed-line analog telephone systems. The pair of copper wires that ran from a central switch office to a subscriber's residence or business was referred to as a "subscriber loop". Each central office housed an enormous bank of lead acid batteries used for back-up power in the event of an outage.

Today, only the older parts of the PSTN utilize analog technology and many new telecommunications provider installations utilize digital systems. Advances in digital communications and increased use of fiber optic cable in place of copper wire have greatly benefited the likes of AT&T, Sprint and Verizon. It is much less costly for telecommunications providers to use multiplexed systems that remove the need for thousands of separate copper pairs to each subscriber. Fierce competition among service providers utilizing these technologies to offer a wider range of television, voice and Internet services is also believed to be the impetus for the rapid reduction in analog technology.

Many sorts of devices, including fire alarm control panels, primarily operate via analog signals. The original 48 DC voltage supplied by subscriber analog circuits (known in the industry as POTS or "plain old telephone system") has also declined to as little as six volts of off-hook voltage. As a result, communications between new and existing installations of both fire and security alarm panels have become particularly dicey as of late.

Boxes supplied by service providers to convert signals from digital to analog are a common "patch", but these have garnered mixed results. Unfortunately, increased incidents of trouble alarms have come about from this patch's analog to digital conversion at the subscriber end or the central office, followed by the digital to analog reconversion at the central station.

Technical Clarifications

As with any new technology, there's always trepidation about being the first to implement it. Many dealers and integrators have voiced their fear of a big learning curve associated with anything related to the Internet.

Considering this new alarm communications method relies on the integrity of a facility's Internet or intranet network, it's recommended an IT department or IP provider be involved. It's good to know how this IP alarm monitoring operates. However, given this technology's ease of installation and high level of reliability, it's not necessary to go back to school for a degree in computer programming.

Confusion between IP and VoIP (voice over Internet protocol) also needs some clarification. Instances where both terms are used interchangeably have increased in frequency.

In layman's terms, VoIP is a combination of hardware and software that enables people to use the Internet as the transmission medium for "voice" telephone calls, or in this case, fire alarm signals. When VoIP transmits a phone conversation or alarm signal, these analog tones are diced up into numerous digital "samples" of data and sent via the Internet (see diagram accompanying article).

It's not uncommon for a couple of these digital samples to be dropped during the transmission. This is called analog to digital sampling and accounts for those instances when a syllable or two are dropped within a conversation using two regular, landline phones. This same scenario can happen to VoIP fire alarm panel communications whereby a sampling of alarm tone (DTMF or dual tone multi-frequency) information can be lost in transmission.

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