An apparatus for adjusting the mutual distance of several movable elements placed side by side wherein control means are provided to insure that the various movable elements move in a transposition operation, the same distance as determined by measuring means which measure the distance which a first movable element moves. The device includes means for repositioning the relative position of the movable elements such that following the repositioning operation, the various movable elements are maintained at a fixed relative distance from one another, the repositioning being conducted by measuring the distance by which a first movable elements moves and moving the related movable elements in response.
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