shall be mounted within a prewired channel fastened to the fabric
fence post at the midpoint of each section. Outrigger barbed wire
and tripwire may share the same switch. Each taut-wire fence post
shall mount to the normal security fence (chain link) fabric posts
or other barrier via standoffs to position the taut-wire
approximately 150 mm 6 inches from the fence fabric or other
barrier. Mount freestanding taut-wire fence posts in concrete to
support the taut-wire fence system. Each barbed wire strand shall
be pretensioned and clamped to the lever arm of the displacement
switch, such that the lever is in the neutral (off) position;
therefore, the forces applied by the barbed wires are balanced
equal in opposite directions. Tripwire shall be pretensioned in a
like manner. Tripwire shall be linked to the top switch in the
sensor switch channel by a special subassembly that includes a rod
which shall serve as a lever to transfer movement of the tripwire
to the end of the actuating lever arm of the sensor switch.
Abnormal displacement of a switch lever resulting from cutting or
deflecting its attached wire, as by climbing on or through fence
strands, shall initiate an alarm condition. Damping mechanism in
the sensor shall reduce alarm threshold due to slowly changing
phenomena such as ground shifting, daily and seasonal temperature
variations, and winds up to 56 km/h 35 mph. Sensor switch shall
provide electrical contact closure as the means for initiating an
alarm condition, whenever the wire clamped to the vertical center
bolt is pulled laterally in any direction by an amount not over 19
mm 0.75 inch. Housing for switch assembly shall be covered by a
neoprene cap to retain the center bolt (lever arm), which
functions as a lever to translate movement of the attached
horizontal wire into contact closure. When the neoprene cap is
firmly seated on the cup-shaped polycarbonate housing, it shall
function as the fulcrum for the lever (bolt). Upper exposed end
of the lever shall be threaded to accommodate clamping to the
horizontal wire. The lower end of the lever, which is fashioned
to serve as the movable electrical contact, shall be held
suspended in a small cup-shaped contact that floats in a plastic
putty material. The plastic putty shall retain a degree of
elasticity under varying temperature conditions and provide the
sensor switch with a self-adjusting property. This provides the
switch with a built-in compensating mechanism that ignores small,
very slow changes in lever alignment (which may result from
environmental changes such as extreme temperature variations and
ground creepage due to weather conditions) and to react to fast
changes only, as caused by manual deflection or cutting of the
wires. Provide metal slider strips having slots through which the
barbed wires pass. Wires shall be prevented from leaving the
slots by rivets. Purpose of the slider strip shall be to
translate forces normal to the barbed wire to a horizontal
displacement of the sensor. Install one slider strip pair, upper
and lower, on every fence post except where sensor posts or anchor
strips are installed. Separation between slider elements along
the fence shall be [3000] [_____] mm [10] [_____] feet. Attach
barbed wires of sensor to existing specially installed fence
posts, called anchor posts, located equidistant on both sides of
sensor posts and at ends of sensor zone run. Anchor strip shall
be a strip of steel plate on which are installed fastening plates.
Weld strip or otherwise attach the strip to anchor post and ends
of tensed barbed wires wrapped around the fastening plates.
Attempts to climb on fastening plates or on the attached barbed
wires shall cause plates to break off, creating an alarm and
SECTION 13703N
Page 37
Previous Page
