Link 1, rotating about axis y-y, has recess b into which one end of component a enters. The other end of component a enters recess c in link 2. Upon rotation of link 1 about axis y-y, component a aligns itself to the position where axis z-z coincides with axis y-y. Then, with respect to each other, links 1 and 2 accomplish a single turning motion about common axis y-y.
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