A Lone Radio: Ask the Security Alarm and Monitoring Expert

Q Can a radio system alone be used to monitor a fire alarm installation and still meet local AHJ requirements that refer to Underwriters Laboratories and NFPA codes? In other words, can a radio system, connected to a central station, stand alone as a...


Q Can a radio system alone be used to monitor a fire alarm installation and still meet local AHJ requirements that refer to Underwriters Laboratories and NFPA codes? In other words, can a radio system, connected to a central station, stand alone as a communications means for a fire alarm?

A The conventional wisdom is that you must use two telephone lines to monitor a fire alarm and you can use a radio system to replace one of the two telephones. This certainly meets the National Fire Alarm Code, NFPA 72, assuming all of NFPA 72's other requirements are also met. But, it may not be commonly known that there exists several radio-based systems that can stand alone to monitor a fire alarm system.

Radio systems that can be used as primary are systems that mimic two-way wired systems, certain one way radio systems and wireless IP systems. The easiest stand alone radio technology to grasp is two-way Radio Frequency (RF) Multiplex Systems as described in NFPA 72 2002 section 8.5.3.4. A few manufacturers have equipment available today that are listed as two-way Radio Frequency (RF) Multiplex Systems.

The only type one way system that can be used as primary is one that meets the requirements of NFPA 72 2002 section 8.5.3.5. This section of NFPA 72 is uniquely crafted for one way systems that meet certain requirements. The most important requirement is that it requires two independently powered and separately located receivers or repeaters. The separate location requirement is usually met by placing the receivers or repeaters on two towers or building tops.

And Then...
Q Are these the only requirements for such systems contained in NFPA 72?

A The other requirements involve the integrity of the signals from premises to central station, supervision and loading (number of premises units on a radio channel). These requirements are not unlike those for other radio technologies.

The last of three alternatives requires a small leap of faith and is only possible with alarm panels that are already "IP compatible." Virtually every major manufacturer of control panels has announced such products. Many are in use today.

According to the codes, it is possible to use a wireless IP link or wireless IP modem for alarm monitoring. While equipment operating on CDMA and GSM wireless networks are available, this has not yet been reduced to common practice. The rationale is as follows: NFPA 72 section 8.5.4 was constructed to allow the use of IP for fire transmission. IP is IP, wired or wireless. The code makes no reference to the "downstream" equipment or communications technique, other than the fact that a nationally recognized testing laboratory for communications should list it.

Once again, the only requirement is that a national recognized testing laboratory (for example, Underwriters Laboratories) lists the connected communications equipment. UL uses UL 1950 as a standard for such products. This opens the door wide for a manufacturer of a wireless IP link, after attaining UL 1950, to be used as a stand alone wireless link back to a central station. It should be noted at this writing, no manufacturer has done so.

One possible usage is if an IP connected system uses any available broadband connection, such as DSL, and you are concerned about the reliability of the broadband connection, you can back up the wire broadband connection with a wireless IP connection.

This is accomplished as follows: First, you must purchase a simple, low cost, UL 1950 listed router with a port for a back up modem. Additionally, a wireless IP modem is connected to the back up port and configured properly. Whenever the DSL link fails, the wireless IP modem begins to handle the alarm traffic without missing a beat. The central station can differentiate which path is being used by the IP address.

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