“With perimeter security, you have the opportunity to know that someone is knocking at your door, as opposed to waiting until they penetrate your boundary and are standing in your living room,” says Jeanne McGuire, national marketing manager for Perimeter Products of Fremont, Calif. This is the mindset that commercial, industrial and governmental facility operators have adopted post-Sept. 11, 2001.

Since these tragic events, nuclear power plants, water utilities and other medium-to high-risk commercial, industrial and governmental facilities have all re-evaluated their outdoor perimeter security so that catastrophe can be averted.

Recently passed legislation requires that water, electrical and gas utilities conduct vulnerability assessments, called Risk Assessment Methodology (RAM). The legislation also requires that upgraded certified security systems be installed. This, in turn, has driven the demand for exterior perimeter security in the utility sector.

The highest risk applications, such as nuclear power plants, may have as many as four layers of different perimeter security technologies. Most, however, employ two sensor technologies, along with video and/or audio verification, and two-way voice.

Unfortunately, outdoor perimeter security systems have a penchant for causing false alarms. It’s a good thing then that there are a multitude of products available to meet the various needs of applications in the real world.

1 Sensor Does Not Fit All Applications

Needless to say, the cookie-cutter approach to high- and midlevel outdoor security does not work. An installer/integrator must adequately evaluate the risk and the site. Some factors that should be considered include terrain, weather and wildlife. These factors, as well as many others, will influence which kinds of technologies should be used.

The nature of what is being protected also influences how the system is monitored. A maximum-security prison has different requirements than a car lot, yet both need perimeter security. In most cases, on-site response teams handle high-risk facilities, while medium-risk sites can often benefit from off-site or central station monitoring.

Fence Sensors Require Well-Maintained Fences

Despite the wide variety of installations, some basic rules need to be followed to prevent false alarms.

Fence sensors should be mounted on fences that are well maintained and are quiet with minimal vibration. “The condition of the fence is critical,” says McGuire. “You cannot have pieces of loose fabric flopping up against braces. You can’t have hog rings loose and flapping around. You can’t have heavy vegetation growing up around the fence either.” Additionally, privacy fences should not support fence sensors.

Technology Targets False Alarms

Much of the proprietary technology incorporated in today’s perimeter protection systems also helps reduce false alarms. Mark Thomas, sales manager for Beaverton, Ore.-based Fiber Sensys says his company’s fiber-optic fence sensors have mathematic algorithms that weed out nuisance signals.

“They are looking for different signatures that are put out in terms of frequencies that are generated by, for example, the cutting of a fence. This will generate a high frequency that is very sharp and short in duration,” he says. “On the other hand, a climber will generate frequencies that are lower, yet longer in duration.”

Larry Thomas, vice president of ProTech in Reno, Nev., says his company’s dual-technology motion sensor can determine the exact distance a target has to move to generate a valid alarm signal. “We can field adjust the sensor for a specific distance in inches. The most sensitive position in our sensor requires that a target move 4 inches. If something moves less than 4 inches, it is ignored as being a valid alarm.”

Don’t Be Afraid to Ask for Help

All of this technology may be a bit confusing to those who are new to or have only dabbled in outdoor perimeter security. Manufacturers are eager to help. “We are very willing to talk to them when they have a particular circumstance to see how it could be approached,” says McGuire.

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