Long-range communication device

"There were these stones, and if you place them in one of several recesses around the outside of the device, it activates it, and allows you to connect with someone far, far away—across the galaxy, inter-galactically even..."

- Rodney McKay

The long-range communication device is a two-way communication device which creates a psychological and physiological link between the users on each end, swapping their minds into each other's bodies. It was originally created by the Alterans millions of years ago, before they left their home galaxy. A variant of the original was developed by the Tau'ri sometime around 2009.

Overview
The long-range communication device is used in conjunction with the long-range communication stones. When the stones are attached to the device, they create a link with the nearest active communication stone, allowing the user to take control of the person to whom the stone is linked and vice versa. As long as the link is active, the user controls the recipient's body as if it were their own.

The device, thus far, has no known limit to its range; it can function seamlessly over billions of light years. However, it appears to be unable to establish a two-way link over intergalactic distances without the aid of a second communication device on the other end. For example, when Daniel Jackson and Vala Mal Doran used one to connect to the Ori galaxy, the couple they connected were not switched in return until a second device was briefly engaged; when it was disabled, the connection back to Earth was severed. Conversely, a communication device activated by Neeva Casol in the Pegasus galaxy was to create a two-way link between her and Jennifer Keller, despite Keller not having used a communication device in return.

Once a link is formed between two individuals, it cannot be severed until the stones are removed or power to one or both devices is cut off. The Alteran version of this device will maintain a one-way connection without a companion device, while the Tau'ri version will disable the connection on both ends if either side loses power.

The device establishes a physiological link as well as a mental one, linking the well-being of those using the device. Effects such as suffocation will be shared and experienced by both users - it is possible that death in one body will kill both bodies, though this is unproven. The device does not share every sensation. For instance, if a person were to become intoxicated while the device is active, they would only be affecting the host body of their partner; if the device were to be deactivated or disrupted while that person is intoxicated, the user would find him/herself sober in the original body, leaving the other user to feel the effects of intoxication.

Daniel Jackson believed that the device was able to translate from Ancient to English based on his first experience with it, though later events show that the Ori followers whom they communicated with speak English. When Everett Young used the device and swapped with a blueberry alien, he could not comprehend their language, which uses clicks and screeches, nor could he communicate in his own tongue.

Original Alteran device
The original Alteran long-range communication device has a hemisphere-shaped based about two feet in diameter with a crystalline spire coming from the center. There are twelve communication stone slots spaced equally around the base. When active, the spire turns blue. While the specifics of the device is unknown, what is known is that the device draws power from subspace. Once activated, the device is impossible to shut off; it has no "off switch" and any stones attached to it are locked in place. The only known method the Tau'ri have for disabling the link is to destroy the device. A Prior has been shown to be able to deactivate the device without the need for violence.

History
The first encounter the Tau'ri had with a device of this nature was discovered on Avalon in Merlin's vault. Daniel Jackson and Vala Mal Doran used it in hopes of meeting non-ascended Ancients living in another galaxy. Instead, they linked to Harrid and Sallis, heretics who had discovered a similar device outside Ver Eger. The device found in Avalon was destroyed when Cameron Mitchell and Teal'c threw it into the kawoosh of an activating Stargate. The device in Ver Eger was taken to Celestis to be destroyed, but Seevis' contacts in Celestis smuggled it out to Ver Isca before that could happen. Vala, while stranded in the Ori home galaxy, used it to link to Daniel and warn Earth of the impending Ori invasion; however, the device was rendered useless when Tomin shot it with his staff weapon.

In 2008, the Atlantis expedition had an encounter with one of these devices. Neeva Casol activated one while stealing artifacts from a village, switching with Jennifer Keller, who was the last person to touch the related communication stone in Janus' lab. To restore them both to their proper bodies, Ronon Dex shot the device, disabling it.

Ori long-range communication
Though the Ori have not been shown to build a physical version of the long-range communication device, a Prior has shown to be able to duplicate the effect using their powers (likely in conjunction with their staff). A prior in the Milky Way demonstrated this with Gerak, bringing both himself and Gerak to Celestis, whereupon Gerak was converted into a Prior himself. It's not shown if their bodies were being controlled by someone else during the exchange.

Tau'ri device
The Tau'ri, despite not understanding the technology completely, have managed to construct their own version of the device. This variant is a much smaller and box-shaped. The top of the device has a flat panel with five intersecting rings, where the stones can be placed. When a communication stone is placed in one of the five rings, the panel lights up and the link is established.

The Tau'ri version of the device has the advantage of being easy to shut off, in contrast to the original which must be disabled or destroyed (if only due to their lack of understanding in how it operates). It comes with a removable power cell, allowing the user to break the connection at will. Alternatively, since the stones are placed on a flat panel and not attached in any way, they can simply by picked up to break the link.

Unlike the original, outside factors have been shown to disrupt the link to various degrees. Destiny's Faster-Than-Light engine creates a subspace disruption when engaged or disengaged, breaking the link for a few seconds. Heavy weapons fire directed at Destiny's shields will also break the link. Finally, the blueberry alien mind probe will sever the link if used on one of the two users, preceded by a bout of severe pain in the subject. When a blueberry alien that had handled a stone was killed moments before an attempted connection, Everett Young, who had connected to the alien twice before, was unable to connect to anyone, including Earth. The connection to Earth was eventually restored. For this version of the device at least, the link is severed if the user enteres a Stargate.

Another effect of the device not shown with the Alteran version is the transfer of traces of memory from the host body, which can be experienced in the form of brief visions or dreams. This is likely a side effect of the host being exposed to Goa'uld brainwashing technology, as it does not occur under normal circumstances. This version has also been shown to be able to connect to a completely alien species, namely the blueberry aliens, provided they have an active stone.

The device is also able to clear the imprints on stones, rendering them inert until they are imprinted by another person. If the imprint is not cleared, the stone will remain active despite not being place on the panel. The blueberry aliens used their stone a second time to exploit this, connecting with Vanessa James. This presumably worked because Destiny's communication device was active at the time.

History
The Tau'ri had developed the variant of the communication device by 2009. At least one device was stationed at Icarus in anticipation of traveling through the Stargate to the nine-chevron address. When the base came under attack by an unknown force, an evacuation was immediately underway. However, rather than dial Earth, Dr. Nicholas Rush dialed the ninth-chevron address, effectively stranding roughly 80 Icarus personnel aboard the Ancient ship, Destiny. As the last person to evacuate the base, Col. Everett Young spent valuable seconds in securing a device. As a result, he was critically injured as the base exploded and he was flung through the Stargate and across the Gate room aboard Destiny. In the ensuing chaos, Rush discovered the device and discreetly made use of it. Afterwards, the device was used by the expedition to keep contact with Earth and make visits to families, as well as occasionally call in experts when their own experience is insufficient.

During Colonel Young's attempt to make a report to Earth, he switched bodies with a blueberry alien aboard a blueberry alien mothership who had come into possession of a communication stone. After an attack by the aliens, Young used this to sneak aboard the mothership to try to rescue Chloe Armstrong, who had been kidnapped by them. He ended up freeing Nicolas Rush instead, and when Young used a mind probe given to him by Rush, the connection was severed. Rush killed the alien whose body he'd been inhabiting before Young could return. The blueberry aliens later used the stone in their possession to infiltrate Destiny and sabotage its FTL drive, allowing them to mount an attack which Destiny could not flee from. Fortunately, Jeremy Franklin managed to use the early repository of knowledge to bypass the damage and get Destiny to safety.

After switching with David Telford on a scheduled switch, Nicholas Rush has a dream made up of residual memory carried over from Telford in which he learns that Telford is a spy for the Lucian Alliance. In order to prove this and to allow Colonel Young to interrogate Telford, who Young believes is brainwashed, Rush switches with Telford again during a scheduled transfer and poses as him on Earth. Tailed by Doctor Daniel Jackson, Rush makes contact with the Alliance through a cell phone found in a safe-deposit box, but arouses the Alliance's suspicion as he didn't use a code-word to identify himself that Telford would have known. Rush is captured and taken away on a cargo ship and is forced to reveal his real identity. Afterwards, on both the cargo ship and another Icarus-like planet, Rush is forced to work on dialing the ninth chevron for the Lucian Alliance. On Destiny Young interrogates Telford about his actions while using the communications device to report into Earth several times and after Telford proves to be completely uncooperative, even lying to him, Young has Corporal Marsden switch bodies with General Jack O'Neill so O'Neill can help in the interrogation. Even with O'Neill there, Telford refuses to cooperate so O'Neill is sent back and Young vents the atmosphere to Telford's room, killing him, but then revives him. Doing so also effects Rush on the other end of the link, but he too is revived when Telford is. Telford's brainwashing is broken and he reveals all he knows about what's going on including the location of the planet Rush is on, leading to an attack by the George Hammond that forces an evacuation. Rush coming through the Stargate to Destiny in Telford's body severs the connection between the two, but Telford remains free of the brainwashing even in his own body.