Electromagnetic shield emitter
Alien technology found in the Pegasus Galaxy that generates a powerful electromagnetic shield around an area, continuously protecting it from attack by technologically advanced ships and weapons by disrupting their ability to function in proximity. The device appears as a small pedestal approximately waist-high, with large orange lights around it. The emitter can be opened from the top, revealing its valuable a long-lasting internal power source: a Zero Point Module.
The Atlantis expedition found an emitter near a human settlement on M7G-677, protecting Keras' people from Wraith attack for many generations. By rendering Wraith Darts and stunner weapons useless, the device made the village an undesirable target for a culling. But the Z.P.M. could not provide enough power to cover the entire planet for the long-term. As a result it is theorized that whoever built the device also instituted the village's practice of ritual sacrifice -- in order to prevent their society from growing large enough to expand outside the area covered by the shield.
Because it is powered by a Z.P.M. and useful for protecting population centers from the Wraith, it is possible that the Ancients themselves created the emitter. But it is unknown if the device is unique or if there are others scattered on populated worlds throughout the Pegasus Galaxy.
Childhood's End - Rodney McKay puts the inhabitants of M7G-677 at risk when he removes the Z.P.M. powering their shield emitter.