The lengths of the links comply with the conditions: A͞B:A͞E=B͞G:E͞F=A͞D:A͞C=D͞G:C͞F, A͞C²+E͞F²=A͞E²+C͞F² and A͞B²+D͞G²=A͞D²+B͞G². 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, G or F, can be selected as the centre of similarity. The pantograph also accomplishes translational motion of two parallel straight lines, EC and BG. These lines are always perpendicular to line AFG.
$856$LW,P$