Introduction

Fiber SenSys intrusion detection systems offer an extremely wide range of features and customization options that allows our products to integrate well with a variety of fencing styles.  Our alarm processors are designed to be used with mesh style fences, and are capable of being implemented with many other fence styles and other applications. 

Although the alarm processors offer numerous user configurable parameters, fence quality plays a major role in the level of security.  Fence quality is an often overlooked consideration that must be taken into account during the planning and design phase prior to installation.

Conducting a Site Walkthrough

Participating in a site walkthrough is a vital part of the design stage for an installation.  During the site walkthrough, the following questions related to the design of the system must be answered:

• What is the desired level of security?
• Will the fence need any additional repairs before installation?
• Is there a large deviation of rigidity between fence panels and fence posts?
• Will the site need added levels of security in addition to Fiber SenSys?
• How many zones will there be?
• What will be the lengths of each zone?

Higher security sites often implement higher numbers of zones as well as additional levels of security such as cameras and/or microwave barriers.  Military sites typically have a maximum zone size of 100m (110yd), which allows for a identification of where an intruder is located. Before a Fiber SenSys installation is initiated, flaws in the fence should be identified and corrected.  Some commonly overlooked flaws include trees standing near the fence line or large gaps along the length of the fence.  Having a good idea of what to look for and what measurements are needed before conducting a site walkthrough makes the design process faster and more effective.

Testing Fence Deflection

One of the primary considerations that effect the sensitivity of the system is the amount of tension on the fence.  Installations implemented on higher tension fences typically outperform those with less tension.  Having a consistent fence tension throughout is also a vital consideration.  Nearly all chain link fences are built with reinforced sections for stability. Adding additional cable in conduit to these sections adds sensitivity, which is an important technique for making the perimeter consistently sensitive. We refer to the routing of additional sensing material at high tensioned sections as "sensitivity loops."  If the style of fence transitions from a chain link style to a different fence design, a new zone must be added and tuned specifically for the differing fence type. During a site walkthrough, we recommend that the tension levels on the fence be measured.  Higher security installations typically require that the chain link fence has a higher degree of tension.

The fence deflection can be measured using a spring scale (also sometimes called a "fish scale" and can be purchased at an angling store) and a tape measure. According to military standards, high security Priority Level 1 (PL-1) installations must have a maximum of 2 inches (5cm) of deflection from its resting position when 50lb (22.5kg) of force is pulling on the center of a chain link fence panel. For standard lower security installations, we recommend a maximum of 2 inches (5cm) of deflection for 30lb (13.5kg) of pulling force. The fence deflection should be measured at a point when the fence appears to have its least amount of tension.

Conclusion

Performing a detailed site walkthrough goes a very long way in executing an effective and high security installation and is a step that is often overlooked.  The amount of security on a protected perimeter is only as good as the fence quality. Following the fence contruction standards that are set by both Fiber SenSys and the United States Armed Forces ensures the highest amount of protection from potential intruders.