Sonar fence

{{Infobox Location
=Sonar fence
=DHARMA Initiative

The '''high-frequency sonar fence''' was a continuous stream of high-intensity sound waves generated by a series of evenly-spaced pylons surrounding the Barracks. It was built by the DHARMA Initiative. {{crossref}} The range of the waves reached only as high as the top of the pylons. {{crossref}} With the potential to render someone walking through the fence unconcious, or even Life and death them, the waves could cause severe cerebral hemorrhaging to humans who passed through them. Although humans could physically breach the barrier before the sonic waves triggered side effects, the Man in Black could not pass between the pylons or overcome them while the fence was active. {{crossref}} {{crossref}}

==On the Main Island==
===Mentions and encounters===
{{I=Curtain-keypad.jpg=left=200=A keypad is used to enable the fence. The actual keypad is a HID model RKL55. {{crossref}}}}
The sonar fence was first mentioned in the DHARMA Initiative Barracks video, seen by Ben Linus when he first arrived on the Island. The film described the fence as serving to protect the Barracks area from the Island's abundant wildlife. Ben encountered the sonic barrier as a child, while running out of his home. He later obtained the code to deactivate the sonic barrier and, as a test, sent a rabbit through the barrier before crossing it himself. {{crossref}}

Kate, Locke, Sayid, and Rousseau encountered the sonar fence on their mission to rescue Jack. According to Mikhail Bakunin, their prisoner, and the DHARMA cabling map discovered by Sayid in the Flame, the fence extended all the way around the area containing the Barracks. {{crossref}}

Locke appeared to kill Mikhail by shoving him through the barrier. {{crossref}}. After passing through it, he began shaking violently, foaming at the mouth and bleeding from the ears. He collapsed on the ground and appeared to have died. However, Mikhail did actually survive, and later helped save Naomi after encountering Desmond and the others who were attempting to find her. {{crossref}} After he returned to the Others' camp, Ben commented, "I thought you were dead." Mikhail responded, "I am fortunate the pylons were not set to a lethal level." {{crossref}}

After seeing what happened to Mikhail, Locke, Kate, Sayid, and Rousseau made a ramp out of a tree trunk in order to scale the barrier and bypass it. In doing so, they did not break the connection between each barrier pylon, which Sayid guessed was the trigger for the sonic waves. {{crossref}} 

{{I=3X15 MonsterJuliet.jpg=right=250=The Monster cannot pass the sonar fence. {{crossref}}}}
As shown by Ben in his flashback, the barrier could be deactivated. Kate and Juliet encountered the inactive fence while running from the Monster. After crossing to the other side, Juliet entered the code 1623 into a data pad, and after lifting a panel and turning a knob, the fence was reactivated. The Man in Black (whilst in Smoke form) then attempted to attack the pair but was repelled by the sonar fence - which appeared to act as a physical barrier against the smoke. After the Monster retreated, Juliet explained, "We don't know what it is but we know it doesn't like our fences." {{crossref}}

When a young Ben deactivated the fence, he used the code 54439. This code was changed every day according to the orientation film he and Roger watched upon arrival to the island. The fence intensity seemed to be controllable at a continuous scale going from red to green to black, where green was presumably a repelling but less harmful effect. {{crossref}}

The fence was seen in excellent condition after the final skip in time of the Island. Juliet shouted for Daniel to immediately stop as he almost walked through it. Amy faked disabling the fence by using earplugs. Sawyer, Jin, Miles, Daniel, and Juliet walked through the fence, which rendered them unconscious. Richard Alpert managed to get past the fence, and claimed that his people could do so with ease. {{crossref}}

===Early warning system===
{{I=Code14J.jpg=right=200=Locke answers the system's telephones call. {{crossref}}}}
The '''early warning system''', created by the DHARMA Initiative, warned the residents of the Barracks via an automated telephone call that consisted of a woman's voice repeating "'''Code 14-J'''". The system was activated when a WikipediaDuress code was entered to disengage the sonar fence.

In the extended version of the Barracks video, new DHARMA members were instructed how to disarm the sonar fence. They also received an explanatory leaflet from Security. http// "14-J" was their code for trespass of a Hostile on DHARMA Initiative territory, in violation of the truce. {{crossref}}
Alex activated the early warning system after being kidnap by Martin Keamy and the mercenary team. Forced at gunpoint to deactivate the fence, she entered the panic code 1623, initiating the warning phone call at Barracks's house (2004)'s house in the Barracks. {{crossref}}

==On Hydra Island==
{{I=6x08 NewFences.jpg=250=left=Widmore's team assembles their own sonar fences. {{crossref}}}}
After Widmore's submarine arrived on Hydra Island, members of Widmore's team set up equipment appearing to be a portable version of the sonar fence pylons, surrounding the dock area. {{crossref}}

After the retrieval of Jin by Widmore's team, the Man in Black (in John Locke's form) tried to get him back, but he was unable to pass across the pylons due to the activation of the fence. In addition to the dock area, additional pylons had been set up in the meantime on a beach to block passage to the Ajira plane. {{crossref}}

The latter were removed after the plane was rigged with C-4. The fence was temporarily deactivated by Sayid, in order to let Jack go to the cages and free his partners, while the Smoke Monster attacked Widmore's men who were responsible for watching them. {{crossref}}

{{I=Sonic wall season1.jpg=200=right=A fence seen in {{ep}}.}}
* Juliet mentioned "fences" in the plural possibly hinting of other similarly protected facilities on the Island.  {{crossref}}
* A notation near the top of the blast door map stated, "DHARMA Protocol- No stations past security barrier".
* In Season 1, a fence can be seen in the distance. It is likely a real fence in Hawaii that was accidentally filmed. {{crossref}}
* There were keypads or control panels on both sides of the fence. {{crossref}}
* A deleted scene from {{ep}} involved Miles, without any apparent knowledge of the sonar fence, correctly detecting that the fence was inactive.
* One way to bypass the fence was by taking the tunnels underneath the Barracks.  Another was to climb directly over the top of the pylons. {{crossref}}
* The sonar fence was one of the landmarks visible when the Island appears underwater in the flash-sideways timeline. {{crossref}}

==Unanswered questions==
*Why is the Man in Black unable to go through the fence?


esBarrera sónica
frClôture à ultrasons
itLa Base
plBariera ultradźwiękowa
ruЗвуковое ограждение
CategoryIsland locations
CategoryDHARMA Initiative
CategoryIsland structures