From: The World In Your Head by Steven Lehar
Fig. 10.1 (A) A simple control system is depicted as seen in a backhoe, where a fixed deflection of the hydraulic control lever L causes a constant rate of rotation of the arm A. In a more isomorphic control system the lever is moved to the desired angle, and the arm moves automatically to duplicate the angle of the lever. (B) An even more isomorphic system has the arm and its control lever mechanically coupled by a connecting rod, so that the angle of the lever always duplicates the angle of the arm. When pressure is applied to the control lever, a strain gauge on the connecting rod commands the arm to move, and the movement of the arm causes the lever to duplicate that motion.