A Control chair functions by creating a neural interface between the subject's mind and the relevant device, allowing the user to control whatever technology it is interfaced to through thought alone. The interface interprets mental commands given by the user and carries them out, then relays information back to the user for confirmation.
This method of control prevents access to the system through other means, a security measure preventing anyone lacking the ability to use the chair from easily controlling the system without it. Control chairs are usually genetically keyed to a specific species to prevent unauthorized access.
Control chairs by culture
The earliest known version of the Control chair is the interface chair employed on the Ancient starship Destiny. Though its default function is similar to that of a Repository of knowledge, the chair also allows access to the ship's systems if configured to do so. This version of the control chair uses a series of electrodes which connect to the user's head during operation. Arm and leg restraints prevent the user from leaving until the interface is disengaged. The chair is usable by any Human, Ancient or not, but can be very dangerous to users with non-Ancient biology unless extensively modified (hindering many of its functions). (SGU: "Life", "Justice", "Sabotage", "Pathogen")
Later models of the Control chair, employed in various Lantean outposts and starships, have many improvements over the older model. These versions of the chair have no restraints or visible interfaces of any kind, simply engaging wirelessly with the brain whenever someone sits in one. The chairs are built into a large base which lights up when the chair is active and enable it to rotate on command. The headrest also glows blue. Gel-filled sacs are built into the ends of the armrests, which can be manipulated to give various instructions (though this is secondary to the neural interface). When in use, the chair reclines, giving the user a better view of the holographic display that can be projected above the chair. (SG1: "Lost City, Part 2")
Lantean controls chairs require the presence of the Ancient Technology Activation gene to use the neural interface, restricting access to those who don't carry the gene. Depending on the strength of the gene in the user, issuing commands can either come naturally or require significant practice and focus. Chair Interface Aptitude (or CIA) is a ranking system used by the Atlantis expedition to determine how well various individuals can make use of it. Lt. Colonel John Sheppard is the highest-ranked gene carrier, followed by Dr. Carson Beckett. (SGA: "Rising", "Enemy at the Gate")
In City-ships, a single Control chair is present, which is necessary to use the Drone weapons or operate the city's Stardrive. The location of the chair varies; in Atlantis, it is not located in the central tower, while another city-ship had a chair in place of where the Stargate would be. Other major systems, such as shields and sensors, have traditional computer interfaces in the central tower. However, the Control chair grants full access to every facet of the city's operation and so can be used in place of terminals if necessary. On Aurora-class battleships, a less bulky control chair on the bridge is used to control propulsion, navigation, and other basic systems, however as seen on the bridge of the Orion although the captains chair looks the same as the control chair on the bridge of the Travelers Lantean warship, there appears to be no palm scanner in the arm of the chair, which, may suggest that the Orion didn't have a neural interface for the captain. It is likely that all Aurora-class battleship have a secondary chair that serves as dedicated weapons control platform. Like City-ships, this configuration is not uniform, and some ships may have their Control chairs located elsewhere. (SGA: "The Siege, Part 2", "Tao of Rodney", "First Strike", "Travelers")
Control chairs will not activate without a significant amount of available power, well beyond what a Naquadah generator can normally provide, though it appears as though this is more a requirement of the technologies the chair controls (such as drone weapons) than a requirement of the chair itself. A Zero Point Module is usually necessary to initialize them, though the Tau'ri have managed to power one without a ZPM using a Mark II generator rigged to operate in a state of barely controlled overload. In that case, the generator was able to activate the chair twice and fire drones. Ancient warships do not ordinarily posses ZPMs but still posses several Control chairs which can be used casually, further suggesting that the chairs themselves do not actually require massive amounts of power. (SGA: "Rising", "The Siege, Part 2", "No Man's Land")
While many users prefer to use the Control Chair through the neural interface, it is also possible to bring up a heads-up display when using the Chair instead. While flying Atlantis, General Jack O'Neill preferred to call up a HUD rather than use the interface. By imagining the Chair spinning around, he was able to rotate the various displays available to him including a tactical display and a navigation one. (SGA: "Inheritors")
The Control chairs in Ori warships also contain a neural interface (as used by Dr. Daniel Jackson), but can also be controlled using the staff of the ship's Prior as the link with the ship. The back of the chair is formed in the symbol of Origin, though this appears to be purely cosmetic. The arm rests, however, feature small panels with buttons on them. (SG1: "The Shroud")
The platform containing the chair lies in the center of the bridge of the mothership, and there are no other crew stations present. A small window is placed before the Control chair, allowing the Prior controlling the vessel to target enemy vessels and maneuver in battle. While keyed to the Prior controlling the vessel, Daniel gave Lt. Colonel Samantha Carter the necessary information to control the vessels.
Ori Control chairs are also needed to align vessels into position. The Prior controlling the vessel does not need to be in the chair to activate the primary weapon on the mothership, using their staffs to activate the weapons, though they may need to at least be on the platform to do this. (SG1: "Counterstrike", "Line in the Sand")
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