The lengths of the links comply with the condition: A͞B:A͞C=B͞G:C͞F=A͞D:A͞E=D͞G:E͞F. For any configuration of the mechanism, points A, F and G lie on a single straight line. When link 1 turns about fixed axis A, selected as the centre of similarity, and one of the points, F or G, is traced along any arbitrary path, the other point describes a similar path. The mechanism has reversibility since any point, A, F or G, can be selected as the centre of similarity. The pantograph also accomplishes translational motion of two parallel straight lines, CE and BD.
$857$LW,P$