Pin b of link 3 fits into a hole in end a of link 1. Trunnions c of link 3 fit into holes in prongs d of link 4. Link 4 has barrel-shaped head e fitting into spherical half-collars f of link 2. With respect to each other, links 1 and 2 accomplish five turning motions about the three perpendicular axes intersecting at point 0 and about two parallel axes x' -x' and x" -x".
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