Electromagnetic Point Sensor. This device detects a frequency
change caused by the reflected impedance of an intruder entering an antenna's
field. Two oscillators are tightly coupled to the antenna. A change in
sensor adjusts automatically to changes in the background noise level. As
the background noise level increases, the sensitivity is automatically
reduced, but detection range is also shortened.
Geophone Point Sensor. Geophone sensors are normally buried
in the ground to detect seismic disturbances generated by intruders. This
sensor is sensitive to seismic and acoustic energy sources and far-field
effects must be discriminated against.
Point Sensor. Magnetic point sensors contain one or
more magnetometers that
are used to detect the movement of ferrous objects.
Using two magnetometers
spaced at various distances, it is possible to
determine the direction
of motion of such ferrous targets.
10) Infrared Beam Sensor. Exterior infrared intrusion detection
systems can be active or passive. Passive sensors detect changes in thermal
changes in signal power between a transmitter and a receiver. Generally,
multiple beams are employed in columns at the ends of a detection zone. An
intruder passing through one or more beams causes a "beam-break," thus
generating a signal. As this sensor can be defeated by tunneling, seismic
sensors should be used as well.
Exterior IDS Detection at Building Exteriors. Several candidate
options for use at building exteriors are briefly described here.
Ported Coaxial Cable Sensors. In addition to use in the clear
zones between perimeter fences, the Ported Coax Cable System (described in
par. 18.104.22.168) can also be used around the exterior of buildings.
Vibration Sensors. Vibration sensors can be mounted on or within
walls and roofs to detect intrusion attempts at facility exteriors. The
simplest vibration sensor is a mechanical contact switch designed to actuate
when the surface on which the sensor is mounted starts to vibrate.
Grid Wire Sensors. Grid wire sensors may be embedded in the walls
or roof of a building. When the barrier is penetrated, the wire is broken
causing an alarm.
Exterior Closed-Circuit Television
Introduction. This section provides a summary of the function and
placement of CCTV's applicable minimum requirements; and the types of CCTV
equipment available. Sources of more detailed design information include: