Stun/Lethal or Lethal Electrified Fence Design and Construction
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View Between Interior Chain Link Fence and Stun/Lethal or Lethal Electrified Fence
| Fence Design A typical prison electrified fence may be as short as a couple of thousand feet, or as long as a mile or more. Regardless of length, the Stun/Lethal or Lethal fence components located within the space between an institution's perimeter chain link fences will include intermediate posts spaced at approximately 20 feet on center, with 16 or more electrified wires strung on insulators on these posts. Strain posts, which are larger and constructed of thicker steel, are located at the ends of each zone, at changes in direction of the fence wires, and wherever additional strength is needed. The fence is energized at over 5,000 volts. |
| Control System In addition to providing a very secure barrier and acting as a physical and psychological deterrent to escape attempts, the fence design incorporates a sophisticated control and monitoring system that notifies prison staff upon any tampering, attempted breach, or the presence of persons in prohibited locations. Among other things, this monitoring system goes into alarm status if any of the fence wires are cut (causing an open circuit) or shorted. This is done by monitoring the current through the fence wires and the voltage at the receiving end of the wires throughout the system. Rate-of-change compensating circuitry prevents rain, snow, temperature, and other environmental factors from triggering "nuisance" alarms. |
| Fence Power
and Control System Reliability The power side of the fence system includes current-limiting circuits, which enable the fence to continue supplying power to the fence wires even if, for example, a chain or other object were thrown onto the fence. No circuit breakers will be thrown; rather, the fence power system will continue to deliver a Stun/Lethal or Lethal flow of current to the fence wires, and the fence control system will display visual and audible alarms on all of the Stun/Lethal or Lethal fence monitors, which are usually located at the sallyport guard tower, the main entrance guard tower, and central control. Likewise, the RANS voice annunciated radio system will dispatch a similar alarm message that will include the number of the zone within which the attempted breach occurred. A backup generator will maintain power to the fence whenever utility power is lost. Upon loss of utility power, uninterruptible power supply systems will maintain power to the fence control system until the dedicated emergency generator starts and is "on line", producing power exclusively for the Stun/Lethal or Lethal electrified fence and its control system. |