Redundancy Bridges the Communication Gap
“What happens if someone cuts my phone line?” As alarm dealers, we’ve all been asked this question.
It wasn’t all that many years ago when my only truthful answer was, “The alarm signal won’t be transmitted, but your bell/siren will still sound, hopefully scaring the intruder away.”
I can’t count how many times I have used that response, but I have always been truthful with my customers. This was during the time when the only economical method of alarm transmission was the digital communicator (I hate to date myself, but also the tape dialer). Of course, this is no longer the case, given the myriad of alternatives we have today.
Some of those alternatives are physical protection of the phone line, buddy systems – short-range signals sent wirelessly to a nearby home or business – long-range radio, and cellular (voice and control channels). Each has its own set of advantages and disadvantages, and is offered from various suppliers. In addition, central stations can do their part by establishing reliable emergency procedures. Physical Measures Protect the Line, But Not the SignalPhone lines may be physically protected from harm in the first place. Lines that are buried, as opposed to overhead wiring, are obviously better protected. But even buried lines have to emerge from the ground somewhere. There are some products that provide physical enclosures for the network interface, and provide the ability to install tamper switches to be connected to the alarm panel installed at the premises.One of the first electronic devices to detect loss of phone service was the telephone line fault monitor. Line fault monitors are designed to detect the characteristic voltage/current that exists on a working phone line. They typically derive their operating power from the alarm control panel, and their sensing circuit is connected in parallel to the phone line they are supervising. They typically provide a SPDT (single pole, double throw) dry-contact relay output, which the installer can make use of in different ways.Although these devices are great at detecting and locally informing of telco line loss, they cannot send the signal to the central station. They can only inform the occupants that their phone line has a problem.Buddy Systems Notify Neighboring SystemsWhat if the phone line is out of service due to nature, an accident or an intentional cut? An additional option is to install a buddy system.
A buddy system is one that will send a signal, typically via a short- or mid-range wireless transmitter, to a nearby home or business whose phone line is intact and report the alarm from that location’s alarm system. The receiver, the buddy location, would then be connected to a zone on the buddy system, indicating an alarm at the affected location. This could be redundant to its own alarm digital transmission or be connected in such a way—through a telephone line fault monitor as previously described—so it would only activate the buddy signal if the phone line is inoperative. Long-Range Radio Can Stand on Its OwnIn the mid-1980s, another technology emerged. The long-range radio offered a whole new type of alarm transmission. At first, this method was considered as a backup to digital communicators. But today, many of these radios are UL Listed and don’t even require a telco hook-up at all. The product is a two-way system, which means every message gets acknowledged, according to Brian Rockett of AES Corp. In addition, every transceiver is a repeater and so the system grows “stronger and longer” with every installed unit. Finally, as an automatic repeating system, it is not necessary to build or rent radio towers which can be expensive. Cellular Backup Is Available in 2 FlavorsCellular transmission is another method of getting a signal through. One company, for example, offers two distinctly different product lines in this area. One product uses the voice channels of the cellular network and produces a normal landline dial-tone for the alarm panel to “hear.” According to the company, whether it is a fax, access control or digital video system, computer modem, Internet connection, etc., you can plug it into its device.The second product line is a store and forward-type product that uses the control channel of the cellular network. Digital data sent by the alarm control panel is first routed to the company’s communications center to be encoded and decoded. Then, the signal is forwarded to the dealer’s central station.Similar to the company’s product mentioned above, another manufacturer uses the control channel of the cellular network. The company’s product uses a trip input from the alarm control panel for activation. One of the inputs can be connected to the bell output terminals of the alarm control and detect if the voltage is either steady (burglary) or pulsing (fire), and report it accordingly. SAI Establishes Model for Central Stations to FollowSecurity Associates Int’l Inc. (SAI), headquartered in Arlington Heights, Ill., passed a rigorous test when it reported no dropped signals following Seattle’s 6.8-magnitude earthquake earlier this year.SAI’s network consists of two fully redundant host sites, which support four servers that centrally manage alarm traffic for all nine regional SAI Command Centers. Each server has the capacity and resources to support the entire SAI dealer base. A triple redundant frame relay/ISDN network, involving multiple carriers for local and long-distance data services, interconnects all SAI Command Centers. SAI has instituted a Disaster Recovery Plan, which, even before the Seattle incident, was implemented when hurricanes ravaged Florida, winter storms pelted Cleveland and high winds swept through Dallas, disrupting local Command Centers. A customized manual has been created for every Command Center detailing what should be done in a variety of emergency situations, such as how to start the generator if it doesn’t start automatically.
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