A driven load is advanced to a selected position by the rotor of a large angle step motor, the housing of which is driven by a small angle step motor having a stationary housing. Driving pulses are fed to the plural phase windings associated with the large angle step motor under control of digital logic, by means of a slip ring assembly. Driving pulses are also fed to the plural phase windings of the small angle step motor under control of the same digital logic.
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