A general inversion cell, obtained from two random contra-parallelogram linkages, interconnected at the vertices of a parallelogram

It is possible to interconnect two dissimilar contra-parallelgram four-bar linkages by four turning-joints in a manner that permits (overconstrained) motion. These joints are located at the four vertices of a parallelogram. During the motion, the angles enclosed between the sides of this parallelogram do not vary, but the lengths, of which their product remains a constant, do. The overconstrained linkage mechanism, leads to the derivation of an entirely new inversion mechanism. Its inversion-cell is a 6-bar linkage of Watt's type, simply obtained from the combined linkage by erasing two interconnected bars with their turning-joints. One may show that Peaucellier's inversion-cell just appears as a very special case.