Abstract: A manipulandum contained in a portable housing unit adapted for grasping by hand and situated at one end thereof within an area reachable by the thumb without rearranging the grasp. In one preferred embodiment, the manipulandum is a joystick extending a short distance from the surface of the housing, with its center of neutral position being essentially perpendicular to the center line of the elongated segment in the neighborhood of the joystick. The joystick has a fixed number of positions, with each position being contained within a preselected solid angle. An additional control dimension is realized by moving the joystick along its axis, against a resilient spring, so as to activate or make contact with an electrical switch.