Link 1 has slot a-a which moves along fixed slider 2. Link 3, turning about fixed axis A, has slot b-b which moves along slider 4. Slider 4 is connected by turning pair B to link 1. The axis of slot b-b does not pass through point A. When link 1 reciprocates, slotted link 3 oscillates about axis A. Displacement s₁ of link 1 is related to angle a of rotat ion of link 3 by the equat s₁=(e*sin(α-A͞C))/(cos(α)) where A͞C is the distance from centre A to the axis of slot b-b.