Abstract: A digital joystick interface circuit includes a trigger detecting circuit, a flip-flop circuit and a value comparator. The trigger detecting circuit is provided for processing the changes of the voltage or electric currents of a game interface so as to reset the trigger signal of the interface. The flip-flop circuit controls the charge cycle of the game port and causes a counter to start counting during the time delay of the charge cycle. The value obtained by the counter after reading the joystick's coordinate signal or switch signal is compared with that of the comparator. When the two values are equivalent, the flip-flop circuit will reset, achieving coordinate addressing.

Abstract: A joystick including two light gratings respectively and fixedly mounted on an X-axle and a Y-axle, which are arranged at right angles to each other are movable by an operating stick. Each light grating has a series of apertures equally spaced along the periphery thereof. A light emitter and receiver assembly is disposed about said apertures in each said light grating to detect movement of the light grating, and a control circuit receiving signals from the light emitter and receiver assemblies provides a variable delay output signal corresponding to the movement of the operating stick.