Round trunnions b of link 3 rotate and slide along oval guides a of link 1. Square body c of link 3 fits into a square hole in body d of link 4. Link 4 has round trunnions e fitting into holes in prongs f of link 2. With respect to each other, links 1 and 2 accomplish two turning motions about perpendicular axes x-x and z-z, and three translational motions along perpendicular axes x-x, y-y and z-z.
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