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This video presents work done at Sandia National Laboratories.  It shows a microscopic prototype weapon safing device built in SUMMiT V.  The device works based on the concept that the weapon will not arm until two microscopic mirrors are properly aligned to complete an optical path.  In order to align the mirrors, a complex 24 bit code must be entered which then moves two gears into position, completing a gear train.  With the gear train complete, the mirrors can be aligned to complete the optical path and arm the system.