Perimeter protection serves all sorts of purposes, so it comes in many forms. Sometimes you need low-tech solutions, such as fencing, lighting, concrete barriers, or even an old-fashioned moat. But more often security professionals are turning to electronic devices ranging from simple motion detectors to video systems that rely on so-called intelligent video software.
To choose the best perimeter protection system for your site, you must start by considering the effectiveness of the technology for the area, its immunity to false alarms, and your available budget.
Here is a look at a few of the electronic perimeter protection technologies available, along with comments from several systems integrators with experience in designing and implementing successful solutions.
Tattletale Fencing
A cable system—using radio reflectometry—is woven into the fence fabric around several large municipal water facilities. The technology works by pairing two wires within a single, continuous cable. Any change in the relationship between the two wires, such as a cut or pinch, will create an alarm situation. This technology can locate intrusions within 10 feet and graphically display on a map the perimeter and point of intrusion, while directing a PTZ surveillance camera to the spot. Wind and weather do not affect this technology, because it knows the difference between the simultaneous movement of several sections of fence and the independent movement of only one section.
Leaky Coax
For more than 30 years leaky coaxial cable (LCX) has been used as a viable means of perimeter detection, in particular in military, nuclear and airport installations. A facility outlines its fenced perimeter with parallel LCXs buried about two inches underground. By employing two cables, one transmitting an electrical signal and one receiving, this method generates a continuous electromagnetic field above ground. Intruders moving over the cables will disturb the field, leading to detection.
San Jose, CA-based RFI Communications & Security Systems created a perimeter protection system for one homeowner who wanted to know when anyone approached his property—even before coming into contact with the estate’s perimeter fence.“Leaky coax did the job and met the customer’s expectations,” said Brad Wilson, president of RFI.
One benefit of leaky coax is that it is invisible to would-be intruders, making it more difficult to defeat. However, leaky coax may not be the right choice for all environments. Areas that experience extremely cold winters, for instance, may not get the greatest benefit from LCX, because frozen ground and several inches or feet of snow can significantly reduce the sensitivity of the buried cables.
Mircrowave: Oldie but Goodie
Microwave technology is another choice for perimeter protection. Microwave systems use pole-mounted transmitters and receivers to set up a volumetric pattern that works best for perimeters up to 300 feet, although the technology is sometimes used for up to twice that distance. Current microwave systems can interface with video surveillance and access control systems so that breaches are displayed on a monitor and cameras are automatically pointed to provide live video of the intrusion area.
Skip Sampson, vice president of Koorsen Fire & Security, based in Indianapolis, said his company uses microwave technology to protect energy transmission sites and other locations.
“We have found that microwave produces fewer false alarms,” he said. “It may be one of the older technologies on the market, yet it is protecting more fence than any other technology we offer.”
Microwave technology is a little less accurate than some other systems in precisely pinpointing the site of an intrusion. Most microwave systems are accurate to about five feet. And while it is virtually impossible to hide the transmitters and receivers, the system’s visibility may act as a deterrent.
Infrared and Vibration Detection
Two other perimeter protection methods may prove effective in certain settings, but both have built-in limitations that hamper their widespread application.
Infrared systems detect any movement that causes a break in an infrared beam, setting off an alarm. However, this technology requires a straight line-of-sight installation. Outdoor applications are rare, because animals and other non-threatening items can easily break the beams and cause a high percentage of false alarms.
Vibration detectors can be buried at long intervals to protect miles of perimeter. The U.S. Border Patrol uses vibration detectors in largely uninhabited areas of the Southwestern states along the border with Mexico. This technology requires a quiet environment, making it ineffective for areas with regular vehicular traffic or movement of large numbers of people or animals.
Cameras Work Where Others Don’t
The wave of the future in perimeter protection seems to be the use of video. The camera is becoming the point of protection. It serves as the only option in certain instances. For example, a steel company wanted to protect its shipping facility on one of the Great Lakes. It was too large and active an area to make older perimeter protection methods cost effective, and the environment was hostile in winter. Only a wireless video system, monitored around the clock by company security personnel, would work.
One of the latest technologies to enter the market is known as intelligent video or video analytics. Intelligent video uses software to automatically and continuously analyze live video images and generate alerts when violations of user-determined criteria are detected.
Unlike the technologies we’ve discussed so far, video analytics use highly complex algorithms to determine differences between non-threatening events, such as windblown paper, and threatening events, such as moving people.
Users can create rules so that the software will alarm on any object left unattended in a critical area, or any car parked for more than 10 minutes in front of an airport terminal. Alerts are created if people or vehicles cross virtual tripwires drawn on video displays by the user.
By automating video monitoring, intelligent video software improves the performance of on-site security personnel by permitting them to extend their coverage to other areas of concern.
While the technology offers tremendous potential, it does have some drawbacks. For one thing, video analytics depends upon light. If cameras cannot detect images due to darkness or inclement weather, there is no video to analyze. As a result, intelligent video works best in interior spaces.
There are thermal infrared cameras capable of providing video of intruders at night or in thick fog or smoke. These cameras do work with intelligent video software, but they can cost as much as $50,000 per channel.
“Overall, video analytics is still very expensive, limiting most of its uses to homeland security and other government applications,” said Jim Coleman, president of Operational Security Systems. “But intelligent video has come a long way and is getting close to being ready for general application. The trick today is to find those narrow applications where the technology fits.”
In the end, the best advice is to work with an experienced systems integrator to determine which solution will fit your budget, the environment and the scope of the project.
Dave Shelton is president of D/A Central Inc., a 47-year-old systems integration company serving Michigan and the northern Midwest. D/A Central is also a member of SecurityNet Inc., an international network of systems integrators closely interacting to serve national-level clientele with local attentiveness at every location.
