Link 1 is connected by screw pair A to the fixed link and by screw pair B to link 2 which, in turn, is connected by screw pair C to the fixed link. Screw motion of link 1 is converted into screw motion of link 2. When link 1 is turned through the angle ϕ₁, the displacement of link 2 is s₂=h_C((h_A-h_B)/(h_C-h_B))(ϕ₁/(2π)) where h_A, h_B and h_C are the pitches of the threads in screw pairs A, B and C. These pitches are taken with a plus sign for right-hand thread and with a minus sign for left-hand thread.
$2201$LS,3L$