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Shield generators are made in a wide array of sizes: from personal shields favored by primitive armies and riot police, to the massive devices produced by generators built to enshroud capital ships in a protective bubble. The planetary shield generator can cover a wide swath of a planet's surface in an impenetrable umbrella. Coupled with an adequate power supply, generators have been documented to include up to nine urban centres in their halo.
While unassuming, simply built structures, shield generators offer enormous amount of protection to a sensitive area. Shield strength can be regulated from its control room to allow certain ships through while continuing to block others. Often, defense complexes for megalopolises will deploy multiple generators to maximize the shield strength over a central location. However, even a single generator will add an extra layer of defense that can give defenders time to rally forces and send out calls for external aid.