Exterior Intrusion Detection Sensors: Exterior intrusion detection sensors are customarily used to detect an intruder crossing the boundary of a protected area. They can also be used in clear zones between fences or around buildings, for protecting materials and equipment stored outdoors within a protected boundary, or in estimating the POD for buildings and other facilities. Because of the nature of the outdoor environment, exterior sensors are also more susceptible to nuisance and environmental alarms than interior sensors. Inclement weather conditions (e.g., heavy rain, hail, and high wind), vegetation, the natural variation of the temperature of objects in the detection zone, blowing debris, and animals are major sources of unwanted alarms. Due to this vulnerability, it is extremely important that enclosures are located and installed properly and that adequate physical protection is provided. Several different types of exterior intrusion detection sensors are available: (a) Fence sensors; (b) Buried line sensors; (c) Video motion sensors