models provide only sensitized areas which must be carefully positioned to
provide adequate protection. Higher cost models provide sensitized points
on the digitized image (the larger the number, the higher the cost) which
then must be desensitized individually, as desired, if nuisance stimuli are
present. Extensive operator training is required to maximize system
d) Changing lighting shades and reflections from standing water can
produce nuisance alarms. The more expensive models have some capability to
reject such nuisance stimuli. Careful camera placement, camera field of
view selection, and configuration of sensitized image areas are more
effective countermeasures against nuisance stimuli.
e) Very large coverage areas require multiple cameras and may
require multiple processors if the maximum capacity is exceeded.
f) Visual masking by objects within the camera's field of view will
g) The most cost-effective application of this sensor to date has
been in large open interior areas where no standing water will be present
and which have a relatively low activity level.
4.2.7 Interior Sensor Summary. Sensors form the "front line" of the
integrated security system. Interior sensors are the last line of defense
in providing protection to sensitive resources. Table 4 provides a summary
of the strong and weak points of most sensors discussed in this section.
Misapplication or "force fitting" of sensor products by vendors can lead to
a false sense of security. Table 5 provides, in summary form, application
guidelines for sensor selection. Table 6 provides more detail in this area
for the most widely used volumetric motion detection sensors. Finally, it
must be reemphasized that quality installation is critical. The most well
designed sensor subsystem will not work if installed improperly.
4.3 Exterior Fence Sensors. Fence sensors are designed to detect
attempts to climb over, lift up, or breach a line of security fencing. Some
types detect climbing better than breaching attempts. Others do the
reverse. Most fence sensors are designed for installation on an existing
fence; others can form a stand-alone barrier themselves. Fence sensors vary
in principle of operation and in ease (complexity) of installation. Some
characteristics are common to all fence sensors: all require lightning
strike protection both for themselves and the fence; all are affected
adversely to a greater or lesser degree by wind; all can be bypassed by
tunneling under or bridging over the fence; and all will perform best on a
well-constructed chain link security fence, designed and installed in
accordance with DM-13.01, Physical Security.