Wire has been the de facto standard in signaling since the early 1800s when it was first used in telegraphy to carry information on enemy troop movements in Europe.
“Bavarian minister Montgelas called in local scientists to develop an optical telegraph, envisioning an apparatus like the semaphore system. But they fashioned something entirely different: a system to telegraph enemy positions using electricity flowing through wires,” writes William Greer, author of “A History of Alarm Security,” published by the National Burglar & Fire Alarm Association.
War often becomes the mother of invention. In this case, it meant the difference between life and death.
Since then, the technology that drives communications has advanced as society’s needs have changed. For example, since the central station concept was first developed in the 1800s (see sidebar), mobile forms of communication have made alarm monitoring easier and faster to deploy. Given our fascination with wireless gadgets, it’s likely soon that radio will become the predominant method of signal transport from alarm system to central monitoring station.
Whether the application involves backup or primary reporting, radio-based systems are a viable means of communications, and their use is growing each day.
Abandoning traditional POTS
The alarm industry has a long and successful relationship with the telephone wire, and it’s still the most used signaling method, although wireless reporting is growing quickly.
“The most common form of communications for burglar [and fire] alarm systems is a telephone line. Most modern alarm panels have a built-in digital communicator for this type of communication,” write Charles Aulner and Bryan McLane, authors of “Low Voltage Systems Design & Installation,” published by National Training Center (NTC) of Las Vegas.
The digital alarm communicator transmitters (DACT) contained in modern alarm panels are specifically designed for plain old telephone service (POTS), which is part of the public telephone switched network (PTSN). A DACT is the portion of a control panel that handles communications with the central monitoring station and transmits and receives data.
Other means of signal transmission usage, such as cellular and the Internet, have affected the alarm business. For example, an increasing number of home and business owners are turning to voice over Internet protocol (VoIP). This often is accomplished using a broadband connection, such as digital subscriber line (DSL) and data over cable.
Because traditional alarm panels are designed for POTS-based communication, problems have arisen when clients switch from conventional POTS/PTSN to DSL or data over cable. In this case, the DACT is unable to consistently connect with the central station receiver. The result is less than reliable operation.
Redundancy by radio
The disappearing telephone wire can be replaced by using long-range radio technology. Not only will radio address these issues, but it can be used to redundantly back up POTS/PTSN.
The fact is, where there is a hard-line telephone wire, metallic or fiber, there’s the propensity for communication disruption. Common failures include unintended mechanical failure and deliberate sabotage.
In the life safety arena, alarm technicians often make use of radio technology as a backup signal path to a hardwire cable. This is done to satisfy Section 220.127.116.11.1.4 of the National Fire Alarm Code, NFPA 72, 2007 edition.
NFPA 72 calls for two or more paths for alarm and trouble signals. One way for that is to use a single telephone circuit with a backup radio system. Possible selections for the backup include cellular and traditional private or public long-range radio. The code also mentions others. For a list of the criteria for acceptable backup signaling methods, refer to NFPA 72, Section 8.6.4.
Often, the same radio technology some installers use for backup communications also can be used in lieu of a cable. Fire and burglar alarm systems often are monitored this way.
Public or private?
There are two basic types of long-range radio systems available today: public and private.
“Public radio networks provide all receiving and control hardware for the network and charge network users a fee to use the service,” write Aulner and McLane. “Service is usually offered in multiple geographic areas and allows alarm signals to be retransmitted to anywhere in the country. Private radio networks are typically local networks owned and operated by local companies to provide local wireless monitoring to their local customers.”
AlarmNet by Honeywell, IntelliNet by AES, Keltron’s Life Safety Alarm Monitoring, AlarmLink and Bosch’s Safecom all are examples of private networks. Uplink by Numerex, DSC’s GSM transceivers, Telguard Digital by Telular Corp. and DMP’s Digital Alarm Radio all are examples of public radio networks.
A typical private long-range radio system consists of a single-point transceiver mounted on a tower. When the area of coverage exceeds the capability of a tower, repeaters are positioned throughout the intended areas of coverage.
The central tower typically receives radio telemetry signals from single- and bidirectional ancillary radio reporting units connected to burglar and fire alarm systems. Repeaters extend the reach of the main antenna. The frequencies used are allocated to a local entity that, in turn, includes the lease for the radio service as part of a monthly monitoring and service fee to individual alarm owners.
Public radio-based long-range radio systems differ. These networks usually are quite extensive, and they support more than just alarm telemetry data. The commonly used cellular network is a good example because some stretch across the entire United States. In other cases, the owner of the cellular network may just cover regions or entire states.
Benefits of mesh technology
Traditional long-range radio has worked fine for many decades, but mesh networks extend the reach of the central station in an affordable manner.
Traditional long-range radio requires the use of expensive repeaters. Instead of spending a ton of money on repeaters, alarm companies can build their own network over time by installing an interactive network that centers on subscriber transceiver units that, themselves, act like repeaters.
“Mesh technology is a multinodal technology where, from an AES standpoint, the brains are in the transceivers that make up each of the nodes that make up the network,” said John Milliron, national sales manager for AES Corp. of Peabody, Mass. “Each transceiver in a network has the ability to optimize itself to most efficiently bring back the information they’re responsible for transporting to the receiver.”
Each subscriber transceiver in a mesh-type network is capable of routing information in multiple directions using multiple subscriber units. Because each subscriber unit also acts as a repeater, the central receiver can get data through any number of subscriber units. In a private or cell-based system, when the one cell/repeater tower goes down, the data from the subscriber unit that depends on it for communication will not reach the central station.
Keltron Corp. of Waltham, Mass., also offers a long-range radio system that uses mesh technology.
“The mesh network that is created is constantly monitored for optimal performance and reliability,” said Keltron CEO David Wilbourn. “Distributed intelligence and dynamically evaluated transmission paths ensure that the system always uses the most reliable path to the central receiver.”
Keltron’s mesh technology is widely used in the institutional marketplace, such as colleges, universities and government.
“Large multibuilding facilities choose the Keltron active network radio system because it leverages their existing investment in fire alarm control panels, enables them to choose nearly any brand of equipment, eliminates expensive telephone or direct wiring, and is highly scalable for future expansion,” said Steve Sargent, Keltron director of sales.
Keltron can decipher alarm signals from anyone’s fire alarm panel. These signals are then forwarded to the central station for action, using a common communications format.
Both Keltron and AES systems operate on the distributed intelligence concept where every subscriber unit has the capacity to route signals from other interactive subscriber units to a main radio receiver at a centralized location. Not only does this eliminate the need for expensive towers every 20 to 50 miles (near line of site), but it also eliminates the need for maintenance and other ongoing costs typical of a multiple-repeater system.
NFPA 72, Section 18.104.22.168, lists the requirements for two-way radio frequency (RF) multiplex systems. Since both of these mesh-type networks qualify for Type 4 classification under Section 22.214.171.124.4.1, alarm companies that use them do need POTS. Type 4 systems must be situated so they are in constant and ready contact with at least two RF receiving sites. The system also must contain two transmitters that have the ability to either supervise all RF transmitters on-site or dispersed throughout the site among all the other RF transmitters. Failure of any RF unit must be reported to the supervising station.
Each subscriber unit knows exactly where it resides within the network by listening to all radio traffic on the network. Each node is able to determine its relative position in the network, routing signals in the best way possible, for clarity and redundancy. Wireless long-range radio just may be the way to go.
COLOMBO is a 32-year veteran in the security and life safety markets. He currently is director with FireNetOnline.com and a nationally recognized trade journalist located in East Canton, Ohio.