Process by which the user of an Ancient communication stone interfaces with a power source to take possession of another person across a distance. The individual on the opposing end, with their own power source, may be standing by as a receptacle. In this case, two-way transference occurs and each individual take possession of the other's body.
In another scenario, when there is no communication stone active on the receiving end, the individual initiating the transfer may instead take the body of a person who has possession of a stone. In this case, one-way transference occurs and the consciousness of the receiving person is suppressed until the foreign consciousness disconnects. There are other circumstances, however, where only one stone is needed to swap both bodies, such as with Jennifer Keller and Neeva Casol.
It is not clear what causes the outbound user to connect to an individual not using a stone, as demonstrated in the latter scenario. It could be that a conscious effort is made to select a specific person, as Vala Mal Doran once did with Daniel Jackson.
Stones created by the Ancients must be activated with an Ancient gene before they can be used. Once this is done they appear to be permanently activated. Stones developed by Earth scientists can be used by anyone, including certain alien life forms.
Citizen Joe - Joe Spencer and Jack O'Neill, two men with the ancient gene, unknowingly activate Ancient communication stones and glimpse visions of the other individual's life over seven years.
Avalon, Part 2 - Daniel Jackson and Vala Mal Doran activate two communication stones in the Milky Way galaxy and take over the bodies of Harrid and Sallis in the Ori Galaxy, suppressing their minds.
Origin - When Daniel and Vala are to be burned on an Ori altar as heretics, Mitchell and Teal'c destroy the communications terminal and sever their connection. Harrid and Sallis are left to burn instead.
Crusade - Vala, in the Ori Galaxy, takes the body of Dr. Jackson to warn Earth of an impending Ori assault.
Identity - Neeva Casol occupies the body of Jennifer Keller in Atlantis, while Keller is placed in the body of the hardened criminal.
Air, Part 2 - Dr. Rush explains the purpose of the communication stones to the Destiny crew, having already made contact with General O'Neill at Homeworld security.
Air, Part 3 - Colonel Young and Chloe Armstrong swap bodies with Colonel Telford and Dr. Mehta on Earth to exchange professional and personal information.
Darkness - Colonels Young and Telford trade bodies again, with Young visiting his wife home on Earth ... and Telford attempting to get Young replaced on the Destiny.
Earth - Young, Wray, Eli and Chloe trade bodies with people on Earth, giving Colonel Telford an opportunity to take command of the Destiny and enact a dangerous rescue plan.
Life - Wray and Scott return home to visit their loved ones using the stones.
Space - Young inadvertently trades bodies with an alien while trying to report to Earth, and later takes advantage of the connection to find his abducted people.
Divided - The crew use the stones to bring a surgeon, Dr. Brightman, on board in Chloe's body in order to remove an alien tracking device from Rush's chest.
Sabotage - A brilliant scientist from Earth, Amanda Perry, spends several weeks on Destiny in the body of Camille Wray, who in turn visits home in Perry's quadriplegic body.
Subversion - Dr. Rush surreptitiously trades places with Colonel Telford to prove that he is a spy for the Lucian Alliance, leaving Telford in Rush's body to be interrogated by Colonel Young.
The Greater Good - Ginn and Amanda Perry trade bodies, and both are presumed dead after Simeon kills Ginn's body on board Destiny.
Alliances - Camille and Greer trade bodies with people back on Earth, only to find themselves in the middle of a Lucian Alliance attack.
Hope - Chloe's body is taken over by Ginn, whose mind has been adrift since her body was killed.
Seizure - Colonel Young and his team use the stones to trade bodies with Kelownan personnel, in order to use their ally's Stargate without their permission.