Link 1 has round rod a fitting into hole b of ball-shaped link 3. Spherical surface e of link 3 fits into spherical bearing g in which it is held by cover f having spherical collar e. With respect to each other, links 1 and 2 accomplish three turning motions about the three perpendicular axes intersecting at point 0, and one translational motion along axis y-y.
$86$EM,MJ$