How Do Your Alarms Communicate

By Rich Abrams, CSS
January 2001
Reprint Protection News

There are many ways that a signal from a fire or burglar alarm can reach the receiver; from POTS (the telephone line that you talk on every day) to sophisticated radio transmitters that seem to have been designed for the CIA. Whatever method your security system is using, the important function is to get the correct data from the device (motion detector, heat detector, door contact, etc.) to the base station where dispatching occurs.

The oldest method (except for smoke signals from our Native American friends!) is the regular telephone wire. In the older systems, each account leased a copper wire connecting them to alarm company central station via the local telephone company switching station. Developed in the 1870’s to measure changes in current at a box in a store or home, it is still used by many private customers. One problem is that the communication flow depends on a solid connection between the two points – if a wire is cut on a pole, the earliest systems show an alarm. Over the past few years, telephone companies have begun to phase out this type of service, since maintenance costs are high and switching equipment is dated.

The answer is derived channel monitoring – where the phone company provides a special device at the switching station and another at the alarm company. The digital signals are then monitored by the phone company for quality control – so line faults can be reported and alarms transmitted more securely. Please note this system is an option: not available in all areas of the country.

A third source may use a cell-phone similar to what you probably carry with you today. It was marketed in the 1980’s and allows the alarm user to transmit data on the same system that local cellular phone companies provide. There is a charge, of course, as you are paying for the phone number and usage. A typical system has an alarm control interface, a cell phone mounted in a cabinet with back-up power, and an outside antenna if needed. This device allows for alarms to be transmitted even if local phone service is down, providing that it can "hand-shake" with a cellular tower site. Upgrades are ongoing, such as the same technology that allows you to operate your laptop computer in the car. (Telemetry)

Another plan of action is radio, again this is a newer technology developed in the past twenty years. The simplest type simply substitutes a two-way radio (such as your officers use in the field) to transmit alarm information from one building to another instead of a phone line. This requires a dedicated radio channel as well as line-of-sight reception. A better solution is becoming part of a commercial network, where tower sites and equipment are maintained by a private company and channels are shared based on repeating the messages from office building roofs, water towers, mountaintops and other elevated locations.

Whatever method that your security department chooses to move the alarm information from the point of occurrence to the receiving station, make sure that you can provide interference-free data and your staff is able to interpret and dispatch the information. As technology grows into the twenty-first century, new ideas about alarm transmission will be unveiled and older technology will be challenged by parts shortage, lack of technical support, or noise on the line. This article does not offer any specific vendor names or ultimate solutions – but I hope that you will examine your burglar and fire alarm system with an eye toward data transmission.

Rich Abrams is employed by Yale University Security Office in the central alarm station. He is a former police and fire dispatcher with fifteen years of experience in alarms and emergency communications, and a member of IFPO and ASIS