In this paper, the synthesis of a spatial mechanism with a 4C topology (four cylindrical joints) to generate a dual mathematic function is presented. The mechanism has two real degrees of freedom (2 DOF) and each of them generates an output function. The dual algebra is used as a convenient tool for solving problems with topological features of this type of mechanisms. The design equations are separated into two parts: the first one is the primary part and the second one corresponds to the dual number. The numerical solution of the equations are given and verified by computer simulation.