An active E.M.P. Beacon.
The E.M.P. Beacons are a series of devices around the perimeter of Sand Blast City that emit an electromagnetic field. Designed by Avery the Bear, they serve as an extra line of defense against the Great Desert Dark Egg Legion; any Legionnaire who happens to wander within range of a beacon risks having his or her cybernetics disabled. (StH: #217)