Personal shield emitter

The personal shield emitter, less formally called an invincibility device, was a palm-sized device created by the Ancients that, when placed on the body of an individual with the ATA gene and then activated, will generate an advanced dampening field that prevents penetration by objects such as bullets and energy weapons, as well as allowing the user to perfectly withstand a fall of almost any altitude, exotic energy particles, and even energy-absorbing creatures.

When the shield is active, nothing is permitted to pass into or out of the person's body, without practice. As such, the shield can prove problematic to an untrained user. Due to its innate purpose of deflecting solid and liquid objects, the shield can prevent the user from eating or drinking while the device is active if they are not mentally skilled enough to change it's setting ( experienced users have been known to eat and drink while wearing the shield.) Also, as the user still requires air to breathe, he would not be protected from drowning or being buried alive.

Even the user cannot reach the emitter to disconnect it. A mental command is responsible for deactivating the device, although the user must be trained in the proper mental disciplines lest his subconscious will override his conscious desires in the use of the device. For example, the user may consciously believe he does not need the shield, but his subconscious mind may realize the shield is needed, and the shield will stay active until the danger has passed. In addition, if the subconscious mind realizes that wearing the device places the wearer in a situation that is disliked, the shield will deactivate. Some of the shields can only be used by the first person to activate it and will not respond to anyone else, although Lucius Lavin possessed a variant that could be used by him and others ie. John Sheppard.

The devices do not appear to be rechargable, at least not to the knowledge of the Atlantis Expedition, but there is probably a way to replace it's power cells if recharging is not possible.