A four-bar parallel linkage, with no links fixed, used as a copying device for generating geometrically similar figures, larger or smaller in size, within the limits of the mechanism. In the illustration the curve traced by point T will be similar to that generated by point S. This similarity results because points T and S will always lie on the straight line OTS; triangles OBS and TCS are always similar because lengths OB, BS, CT, and CS are constant and OB is always parallel to CT. Distance OT always maintains a constant proportion to distance OS because of the similarity of the above triangles. Numerous modifications of the pantograph as a copying device have been made.