Magazine Articles

Military Technology Applied to Municipal Fire Alarm Systems

IMSA Journal
January/February 2002

The US military developed a proven radio based technology and is now making it available for private industry applications. Keltron Corporation, a long time manufacturer of municipal alarm monitoring systems, has integrated the technology to create a wireless fire alarm radio network.

The network uses a unique two-way, digital packet data approach ensuring end-to-end supervision. Each remote subscriber transceiver unit functions as a node in the overall network allowing packets of data to flow through the network using a store and forward concept. This signal transmission format eliminates dedicated repeaters, tower sites, rental fees, and critical signaling paths. The network is in a continual state of developing dynamic, self-routing and redundant paths from each remote subscriber to the head end receiving location.

The self-healing capability of the technology insures continued operation when a subscriber discontinues service or a transceiver fails. Because every message sent in the network is acknowledged and each transceiver is programmed to periodically send check-in signals, the entire network is supervised. Once the remote transceivers are programmed with an account number and proprietary cipher code, they will automatically enroll in the network after powering up.

The robust nature of the network has earned it listings under numerous Underwriters Laboratories (UL) standards including Remote Supervising Station Fire Alarm Systems. The National Fire Protection Association (NFPA) Chapter 72 code is also met by the digital network paving the way for acceptance by insurance companies and underwriters as well as fire chiefs and inspectors nationwide.

Network benefits include ease of use, simple programming and installation and virtually no ongoing maintenance. Being an extremely cost effective solution for replacement of dedicated telephone lines provides a path to orderly and phased transition to this state of the art technology. The head end alarm receiving and annunciation equipment accepts older style signaling technologies, such as reverse polarity, tones, coded signals and digital communicators when needed.

All received signals are presented to the system operator in simple field-programmed ENGLISH text. The information presented includes the event type with date and time stamp, as well as location identification, and suggested response instructions and procedures. Network operators can program new subscriber units locally or remotely, thereby avoiding expensive installation charges. Unlike cellular or telecommunications systems providers, the technology is user owned, avoiding recurring fees and high sign up costs.

Reliable and virtually instantaneous reception of remote signals is insured by design. The network grows in size and strength every time a transceiver goes on line. The "cellular" like structure of this peer-to-peer radio network adapts to any terrain, changes in environments or the network, and atmospheric conditions by selecting the most optimum route available from a list of routes stored in transceiver memory that are being constantly and dynamically evaluated.

Software Applications

Software in the alarm receiving system provides a field-programmable database of instantly retrievable event messages and a test mode to minimize needless operator interruption, as well as interfaces to CAD or pocket pager systems. Programmable outputs can be used for a variety of critical functions, including coding horns and other devices. Redundant systems, master clock interfaces, remote programmability, historical reporting and multiple operator positions provide the system flexibility required to meet even the largest and most demanding municipalities needs. A sequential rotating event display, two color printing, and event reporting prioritization insure all system information and resources are available to the operator when needed. Printers and printer interfaces are also available.

System maintenance software runs on a PC that is not required for network operation. Accessible are indications of network conditions including routing paths, subscriber unit programming parameters, and network unique indicators such as network connectivity (Netcon) and link layer. Text messages can also be sent between the subscriber unit and the system maintenance PC to facilitate troubleshooting or to provide emergency communications.

Subscriber units may be polled by the head-end to ascertain their status immediately upon request such as after severe inclement weather. Signals to a subscriber unit from the head-end can be forced through a predetermined routing path to aid in network troubleshooting as well as remote programmed which can save countless hours of labor.

Proprietary technology is used to insure that reliable communication paths are always available. Cipher codes insure that multiple networks operating on the same frequency within the same area do not conflict with one another. Each subscriber unit self-tests to further increase system integrity. Active collision avoidance protocols insure each transmission is made without collision by other subscriber units. Distributed intelligence insures the network provides optimum performance at all times. The system is also self-supervising and provides both audible and printed indications of any internally detected faults or malfunctions in supervised modules.

Technical Aspects

Subscriber transceivers feature alarm panel interfaces that vary from simple dry contact or polarity reversal inputs to smart interfaces for digital communicators and intelligent addressable Fire Alarm Systems. Consequently, the system implementation can be as simple as reporting general or zoned alarms or it can report events by specific addressable point.

The system is virtually jam-proof and each network contains a unique owner code to prevent unauthorized use and increase system integrity. The networks typically operate in the 450 to 470 MHz operating frequency and meet FCC narrow band requirements.