The lengths of the links comply with the conditions: B͞C=D͞E and B͞D=C͞E, i.e. figure BCED is a parallelogram linkage. Point G of link 3 lies on a straight line passing through points A and F of links 1 and 2. For any configuration of parallelogram linkage BCED, points A, G and F 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, G or F, 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.
$849$LW,P$