The lengths of the links comply with the conditions: B͞P=B͞D and A͞B>B͞P. Links 1 and 2 turn about fixed axis A which is the centre of inversion transformation. Links 3 and 4 are connected by turning pairs B to link 2 and by turning pairs P and D to sliders 5 and 6 which move along axis Aa of link 1. For any configuration of the mechanism points A, P and D lie on a single straight line. When point P or D travels along any arbitrary curve, the other point describes a curve which is the inversion of the first curve. Hence, the mechanism accomplishes inversion transformations of the form A͞PxA͞D=A͞B²-B͞P²=const.
$1371$LG,GI$