How2Day: Communication Methods of Fire Alarm Systems

There are several communication methods of fire alarm systems due to improvements that have been made with wireless technologies. The older methods used existing telephone lines and secure call boxes for communication. The National Fire Alarm Code provides requirements for the newer wireless methods. The reliability is basically equal for each method. There are advantages for some methods in extreme circumstances, such as dense urban settings or campus arrangements.

Coded radio boxes are used by municipalities when there is no copper-based, copper cabling within a single network or infrastructure. They are used as master boxes to transmit alarms from protected places for public fire reporting. They require a primary power source as well as a backup power source. According to Fire Alarms Center, coded radio boxes can be powered by a utility distribution system, power supplied by the user, or by batteries. Coded radio boxes eliminate the physical problems and high costs of metallic conductors. For example, it eliminates extensive cabling in the fire protected area, which is expensive to install and vulnerable to damage.

DACS are most often used with dual telephone lines, but they can be used with wireless technology. According to Bunker's "Fire Alarm Systems Go Wireless," DACS' are required to use a primary land-based telephone line and a secondary means that can be any of the following: "a cellular telephone connection, a one-way radio system, a one-way private radio system, a private microwave radio system and a two-way RF multiplex system."

Cellular transmitters use cellular telephone networks for communication. These transmitters must be listed for use with DACS since DACS uses a cellular transmitter paired with a land line. Thus, cellular transmitters give enhanced security against land based telephone outages from vandalism or other damage. It's advantageous to use cellular transmitters; they are inexpensive, available and reliable because they use the same widespread, established cell network.

Radio frequency transmission communicates between a supervising station and the protected area through a One-Way Private Radio System and Two-Way RF multiplex systems. A One-Way Private Radio System cannot receive alarms, but Two-Way RF systems will transmit the data in both directions. These systems are best suited for dense urban and campus settings.

DARS do not require dedicated receivers located in a specific geographic area because transceivers act as repeaters for transmitters. A repeater is a radio receiver and a radio transmitter that receives low-level signals. The repeater sends the signals at a higher frequency, allowing the signal to cover longer distances without degradation.This method is very reliable because the signals have multiple pathways to the supervising station. They do not rely on cellular technology, and are safer during telephone outages.

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