J-Link

== Overview ==
Junction links, more commonly known as J-Links are the connection junctions where Snowpiercer's segments of cars are able to connect / disconnect. 
Interior: The interiors differ from the grey-blue standard links, featuring blue and teal stripes painted on the walls. At the center of either side are small windows. At the back left of the J-link is a teal and orange box on which contains the manual locks to arm / disarm the connection process. 
Exterior: It appears as though there are canonically different styled J-link exteriors seen throughout the show. In S01 EP09, The 3rd Class J-links have a box-like connector featuring 2 levels. Above is the doors to pass through each cars hallways, and below is a garage-like door which seals off the Subtrain corridor. In S02 EP10, the aquarium J-link appears to be a shorter version of the standard car link. In S03 EP03, when the derailed cars of the Pirate Train are uncoupled, the link between the carriages is again the standard car link exterior. 
With the inconsistent history of the VFX department and external footage on the show, it is possible the team didnt bother to create a first class J-link exterior and just used the standard links instead. It is also possible the shows budget and timeframe could have played a role in this. 
== Technology ==
File:Lever box.png
File:J-link signs.png
Lever Box: The Lever Box houses instructions as well as a small metal lever used to arm / disarm the decoupling process. In order for the decoupling process to be successful, the Link operator must pull the lever at the same time an engineer turns the J-Link keys in the Engine. The J-Links cannot be released if the train is on lockdown, with an exception being the ones in the Aquarium car. 
File:J-Link Door Seal.png
Door Seals: Once a J-Link decoupling is triggered, the operator has just a few second to exit before a circular door seals off the link in both directions. The circular doors also feature windows to view either into, or out of the link. 
== J-Link Placement: ==
With J-links spread across the entire train, it appears as though there is not entirely a consistent placement with their locations. In S01 EP09 there is a segment of 7 carriages disconnected. In S02 EP10, there is a J-link placed at the 10th car (First Class Aquarium). In S03 EP03, when Wilford derails the last 4 cars of the Pirate Train, we find out there is a J-link at the rear of the library. 
Some known locations: 
* Before the Incarceration Chamber Car
* At the rear of a battery car, just behind the Primary Classroom Car 12 
* The rear of the first class Aquarium Car 
* the rear of the first class Library car.
* (unknown exact location) between a battery car and an Ag-sec Greenhouse.
== History ==
J-Links were used to disconnect the 7-car segment containing the Jackboot army in Season 1, were attempted to be used to take the Pirate Train in Season 2, disconnect 4 derailed cars (C0005 - C008) from the Pirate Train, and part of Ag-Sec in Season 3.
Big Alice also has J-Links, as 3 cars were disconnected during The First Year Cull of Big Alice.
== Gallery ==
File:Snowiercer-s1ep9-melanie-watches-train-procedure-2.jpeg
File:Jlink1x9.jpeg|Layton in Car 139
File:Aquariumwithlink.jpeg
File:Jlink floor symbol.jpeg
Spicecarjlink.JPG
File:Separationjlink.jpeg