D2-Detection

by Robert Gruber, PSPMaster Halco Security Solutions Group

Previously, we discussed the first 4-D principle--deterrence. Now let’s move on to the second principle, detection.

Realistically speaking, there is no special boundary that will keep a dedicated intruder out, so for perimeter protection, it is important that an intrusion detection system of some sort be incorporated. With an intrusion detection system installed - one that works well, we will at least know when someone is attempting to breach our perimeter. The problem with intrusion detection systems is that there are so many in the marketplace—literally, a plethora—that choosing the right one for your needs requires understanding a variety of different technologies. Just look in a trade magazine to see mechanical “shaker” systems, electromechanical vibration sensors, taut wire, video, fiber optic, and the list goes on and on…

The most important thing about deciding which technology to use is to identify the characteristics of the medium to which the intrusion detection system will be attached. You probably would not want to put a mechanical shaker on a very rigid decorative fence, nor would you want to use a copper wire incorporated sensor around a high powered antenna field. This is where it becomes important for the security integrator to be as familiar with the type of deterrence barrier as he is with the type of detection sensor. Unfortunately, many security technicians will just grab the first available intrusion detection system in his inventory and attach it to the fence he’s working on. It may or may not work properly. Although most sensors are sophisticated enough to prevent false alarming, there could be a great deal of nuisance alarms due to using the wrong system. Nuisance alarms are those which are legitimate because the sensor picked up activity it was designed to look for, but it was not the activity of ultimate interest related to security protection. On the other hand, in the case of the “shaker” being used with a very rigid fence, there may be no alarm at all, in a situation where one is definitely needed. Bottom-line, the deterrence and detection systems must correspond with perimeter security goals, usage patterns, and appropriate materials.

If economically feasible, it is always a good idea to build a bit of redundancy into an intrusion detection system. The practice of installing multiple types of sensors for intrusion detection (all, of course, being appropriate for the perimeter), will increase the probability of detection tremendously, and/or will cut down “nuisance” alarms dramatically. It is an “and/or” statement because the use of multiple alarm sensors can be programmed in an “AND” logical configuration, thereby mainly reducing nuisance alarms or an “OR” logical configuration to raise the probability of detection by making the entire system more sensitive.

There are many factors to consider when choosing the appropriate type of sensor(s) for the system. Not only do we have to make sure that the sensor(s) are the right type for the fence and related barriers, but intrusion detection designs must take in environmental, geographical, and psychological considerations.