The virtual reality chairs of P7J-989, designed and maintained by the Keeper, served to maintain the lives of the surviving Residents of the planet in suspended animation as their world, destroyed by an environmental disaster, regenerated itself. Through small puncture wounds in the body, the chairs nourish, stimulate, and control the senses, and channel experience and imagination into and out of the mind. SG-1 became trapped in the chairs, repeatedly reliving past moments of their lives for the entertainment of the Residents.
In the virtual reality created in their own minds, O'Neill relived a failed mission in East Germany in 1982, and Daniel relived the violent death of his parents when he was a child. Carter and Teal'c shared those experiences, however their physiology prevented output from the device that would have allowed them to experience memories of their own, possibly due to having carried a symbiote. SG-1 found a means to escape from the chairs when they were able to convey to the Residents that they were being lied to and that their world was indeed once again a beautiful garden.
The SGC remained in contact with the people of P7J-989 following the incident, and at least two of the chair devices were brought back to the SGC for study. To prevent the possibility of once again becoming trapped in the chairs, the aliens of P7J-989 had altered the design to incorporate the shutoff command into the internal program so that only someone in the chair could control it. Dr. Lee and a team of scientists further altered the design so that a special headpiece interfaced with the user, and Teal'c's physiology no longer prevented him from using the device.
The team worked for two years to modify the chairs to be used as a virtual reality game that could be a viable training tool for SGC personnel. The new chair design allows the game to learn from the player and to incorporate those changes into the programming code. Parameters for various scenarios can be input into the device, but the majority of the simulation array comes from the mind of the user since the programming is very intuitive and is actually built by interfacing the memories from the individual's consciousness with the chair's matrix so that the simulation learns its realism from the person using it and will eventually learn everything that the player knows. To run the simulation, the chair provides the initial parameters, and a data recorder using a new code translation program designed by Carter generates a graphic representation of the player's point of view that can be monitored by the scientists and causes a two-second delay before the player experiences each event in his mind and responds. The player's responses are then incorporated and processed and the result appears on the monitor in a continuous loop of ever-changing data. The chair is capable of using an electric shock to induce a pain response for realism, and while the stimulus itself isn't life threatening, the cumulative effect could lead to a heart attack or lack of adrenaline causing the entire organ system to fail. Thus, it is the player who must determine when to end the game. The chair is designed to reset each time a player is killed, and it will only disconnect if the player completes the scenario or if the player engages the internal failsafe.
In order to allow the programming to learn from someone with tactical field experience, Teal'c volunteered as a test subject during the development of the training scenario involving an invasion of the SGC by Kull Warriors. However, because of the new design, once Teal'c's mind was interfaced with the chair, he could not be forcibly removed from the connection and power to the chair could not be cut without risking serious neural damage or even death. Furthermore, because the chair was able to evaluate Teal'c's character and determine that in a real situation he would never give up under any circumstances, the game would not allow him to engage the internal failsafe to end the game. As a result, Teal'c became trapped within the game, endlessly looping through an ever-changing scenario and growing weaker as the physiological effects of the chair threatened his life. Teal'c was finally released from the chair when a second chair was connected to the first by bypassing the two-second delay and allowing Daniel to enter the game with the effect of two-second virtual precognition, and together they were able to defeat the Goa'uld and end the game.
Cross Reference: Dr. Carmichael, Energy Weapon, Keeper, Kull Warrior, Bill Lee, P7J-989, Residents
Episode Reference: The Gamekeeper, Avatar