| http://www.w3.org/ns/prov#value | - flective means when said first reflective means is not in said desired position; c) directing a beam of light from a light source, said beam have large enough cross-section and aimed, to simultaneously illuminate said first retroreflective means as well as said additional retroreflective means; d) utilizing optical elements, said elements including a cylindrical lens or cylindrical mirror, mounted
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