Round guide (pin) a, secured in link 1, fits into a hole in end b of link 3. Spherical half-collars c, at the other end of link 3, fit over barrel-shaped head d of link 2. With respect to each other, links 1 and 2 accomplish four turning motions about the three perpendicular axes intersecting at point 0 and about axis y'-y' , and one translational motion along axis y'-y' .
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