Abstract: An incremental controller for generating a supplemental positioning signal for use in a display system which includes a graphical positioning device is disclosed. The controller includes an input device, for inputting desired supplemental positioning information. A code generator generates a supplemental positioning signal in response to the supplemental positioning information. A switch is connected to receive the positioning signal and the supplemental positioning signal. The switch outputs either the positioning or supplemental positioning signals in response to receiving a control signal. A controller is connected to the switch for generating the control signal.