fences. Stand aloneStand-alone electric fences act as the sole perimeter barrier. This type is normally found as one of many layers of perimeter security around high security establishments, meaning that in order touch it, an intruder would have had to previously bypass at least one physical barrier. Stun–lethal fence A "stun–lethal" electric fence can be set to deliver a non-fatal shock if touched once, and a fatal one if touched a second time. 12-foot-high "stun–lethal" fences have been in use for some time in many US state prisons, like those in Arizona. The Federal Department of Corrections added them in 2005 to two prisons in Coleman, Florida, and prisons in Tucson; Terre Haute, Indiana; Hazelton, West Virginia; Pine Knot, Kentucky; and Pollock, Louisiana. A "stun–lethal" fence may also consist of two fences; one set of wires forming a conventional pulsed DC non-lethal fence, the second set (interleaved with the first) forming a 6.6kV AC lethal fence, energized when the DC fence detects an intruder. Alternatively it may consist of a single, AC or pulsed DC fence capable of running in "safe", "unsafe" or "lethal" modes by varying the DC pulse energy, AC/DC fence voltage or fence on–off duty cycle. Lethal fence Electric fences designed to carry potentially lethal currents can be used for anti-personnel purposes. In 1915, during World War I, the German occupiers of Belgium closed off the border with neutral Netherlands, using a 300 km electric fence running from Vaals to Scheldt. Germany also erected a similar fence to isolate thirteen Alsatian villages from Switzerland. Electric fences were used to guard the concentration camps of Nazi Germany during World War II, where potentially lethal voltages and currents were employed, continuously rather than in pulses. Some prisoners used the electric barbed-wire fence to commit suicide. During the Algerian War the French erected the electrified Morice Line. Sections of the inner German border were lined with a 3 m (10 ft) high electric fence to deter potential defectors from East Germany. Similarly, the Czechoslovak border was lined with high electric fence during Cold War to prevent emigration from Czechoslovakia. Electric fences are used in similar fashion at some high-security prisons and certain other installations. Typically a nonelectric fence is constructed on either side of such an installation, or the deadly current is carried out of casual reach atop a wall. North Korea uses electric fences to seal off parts of