Abstract: A variable transparency window assembly comprising a plurality of polarizing window elements, the first and second of said elements being fixedly secured to supporting structure with their respective principal axes of polarization mutually aligned and a third of said elements being located intermediate said first and second elements in axially spaced relation thereto and being mounted for rotation with respect to the first and second polarizing elements. The third and rotatable element may be manually or motor driven, and in the latter instance this element may be secured to a partially toothed or geared ring member actuated for rotation through a limited arc under control of connecting motor and gear means, limit means and actuating cam means and a three-position electric switch means.