Electric fence
The effects of the shock depend upon the voltage, the energy of the pulse, the degree of contact between the recipient and the fence and ground, and the route of the current through the body; it can range from barely noticeable to uncomfortable, painful or even lethal.
Early alternating current (AC) fence chargers used a transformer and a mechanically-driven switch to generate the electrical pulses.
Later systems replaced the switch with a solid-state circuit, with an improvement in longevity but no change in pulse width or voltage control.
[3] Companies which have developed this technology include the Norwegian Nofence,[4] the Australian Agersens[5] (brand name eShepherd)[6] and the American Vence.
[7] In many countries such as Switzerland or Austria, virtual electric fences are currently not allowed due to concerns about animal welfare.
In 2023 and 2024, industry-funded studies by the Venn Research Association and Agroscope found their effect on goats and cows to be comparable to traditional electric fences.
[8][9] First published in 1832, Chapter 7 of Domestic Manners of the Americans by Fanny Trollope describes an arrangement of wires connected with an electrical machine used to protect a display called "Dorfeuille's Hell" in the Western Museum of natural history in Cincinnati,[10] which she herself invented.
[11] Published in 1870, Chapter 22 of Jules Verne's Twenty Thousand Leagues Under the Seas, describes "The Lightning Bolts of Captain Nemo" – the use of electrification of a structure as a defensive weapon.
Published in 1889, Mark Twain's novel A Connecticut Yankee in King Arthur's Court, uses an electric fence for defensive purposes.
David H. Wilson obtained United States Patent 343,939 in 1886, combining protection, an alarm bell, and telephone communications.
He constructed an experimental 30-mile electric fence energised by a water wheel in Texas in 1888, which proved successful at keeping cattle separated, but was deemed impractical as a business venture.
[sentence fragment] An early application of the electric fence for livestock control was developed in 1936–1937 by New Zealand inventor Bill Gallagher.
[19] In 1969 Robert B. Cox, a farmer in Adams County, Iowa, invented an improved electric fence bracket and was issued United States Patent No.
Typically, one or more strands of wire, synthetic tape or cord are mounted on metal or plastic posts with stakes at the bottom, designed to be driven into the ground with the foot.
Rapid laying-out and removal of multiple-strand temporary electric fencing over a large area may be done using a set of reels mounted on a tractor or all-terrain vehicle.
For sheep, poultry, and other smaller animals, plastic electric netting may be mounted on insulating stakes – this is also effective at keeping out some predators such as foxes.
Electrified fences are also increasingly used on both domestic livestock and wildlife (game) farms in Africa as a management tool to exclude predators from entering or exiting a camp.
The initial shock will causes the pangolin to adopt its defence of rolling into a ball, often resulting in it inadvertently wrapping itself around the electrified wire.
Pangolins found alive while wrapped around an electrified wire may suffer debilitating neurological damage if they have experienced prolonged exposure to the electric current.
Electric fences are occasionally employed to discourage suicide attempts on tall structures, and to reduce the incidence of graffiti and other petty crime.
Due to the high levels of crime in South Africa, it is common for residential houses to have perimeter defences, such as electric fences.
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 the Scheldt.
[13] 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.
[31] Similarly, the message from the command of the Mauthausen concentration camp to the widow speaks of “suicide by touching the power line,” while the death certificate only mentions that “Doctor Israel Georg Benjamin” died on August 26, 1942 at 1:30 a.m.[32] Hilde Spiel, on the other hand, writes in her autobiography that Benjamin was killed.
[33] A former Nazi prisoner testified to the American Military Tribunal in Dachau, Germany, August 13, 1947 that Jews were forced to jump into electrically-charged fences to be burned death.
The witness, who preferred to remain unidentified because of fear of reprisals, testified that he saw Franz Koffler, one of the accused, beat five Jews and order them to jump into the wired fences.
Sections of the inner German border were lined with a 3 m (10 ft) high electric fence to deter potential defectors from East Germany.
[36] Similarly, the Czechoslovak border was lined with high electric fence during Cold War to prevent emigration from Czechoslovakia.
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.
In a similar system, the collar uses GPS signals to determine proximity to a predetermined "virtual fence" without a physical installation.
