In general, a double fence perimeter configuration having a strain-sensitive
cable taut wire on the inner fence, and MFS or PCCS for detection with a CCTV
(for assessment) in the clear zone is used to protect critical military
resources such as special weapons or designated Command, Control, and
Communications (C3) facilities.
Interviews with representatives from the Navy, Air Force, Army, and
USMC showed general agreement with the above most commonly deployed sensor
choices. In some cases, it was found that a given military service might
interpret differently what constitutes a critical resource requiring the
The following briefly summarizes some important characteristics of
the above sensors. Generic configurations are described since the
performance of one manufacturer's sensor may differ in detail from another's.
Performance is also site- and installation-dependent. Sensors must be
evaluated for their capability to detect targets against which they are
expected to be used, and for their vulnerabilities to the source of nuisance
alarms expected to be encountered. Each sensor has its own vulnerabilities
to natural background disturbances and capabilities for target detection.
For more details see the sources listed in par. 4.5.1.
Strain-Sensitive Cable. This sensor detects intruders by use
of a fence-mounted transducer cable which sends analog signals to an
electronic signal processor when the cable is disturbed. The transducer is a
coaxial cable with shielding (Teflon) between the center conductor and the
shield outer conductor. The incoming signal from the sensor cable is fed
into a signature filter; signals that closely resemble intrusion signatures
pass through the filter, generating a count. If the total count exceeds a
preset limit within a preset time, an alarm pulse is generated. The basic
system consists of a signal processor and a transducer cable. The transducer
cable is typically installed in 328-foot (100-m) sectors, which are monitored
by a signal processor. Each sensor sector provides one alarm output. The
strain-sensitive cable will not detect threats on the fence outriggers. This
requires a taut wire sensor.
"Y" Taut Wire Sensor (YTWS) System. The YTWS consists of a
fence-outrigger-mounted sensor and control unit that employs a twisted barbed
wire pair stretched to about 75 pounds (34 kg). Wire deflections caused by
climbing, pulling wires apart, or cutting the wires produce alarms. The YTWS
system consists of two sensor arms in a "Y" configuration, each with six
sensor switches, dual Expander Isolation Circuit Assemblies, and twelve taut
wires running the length of the sensor sector. Each taut wire is connected
to a sensor switch at the switch arm so that a switch is actuated and an
alarm generated by deflecting any of the taut wires. Slider arms in the
outrigger plane at each fence post maintain taut wire separation along the