This is a combination of two four-bar mechanisms with a common crank(driving link); and different couplers and other links. The couplers are extended and have a triangular shape. A closed curve is thus traced and the symmetry of this curve depends upon the phase difference between the two couplers. The curves would be symmetrical if and only if there is no phase difference between the couplers. The system has five links ( one driver, two couplers and two other links) and they are kinematically constrained by six revolute joints. The system therefore has two degrees of freedom.