A detection system for detecting the position of an object of a movable member and, In particular, for detection the position of a ball in a moving roulette wheel which has a light source for emitting visible light which is modulated. A sensor is provided to receive reflections of the emitted modulated light from the ball and the moving roulette wheel. The reflections are analyzed to determine the position of the member and the location of the objection in relation thereto. The light source can transmit light and the sensor can detect specific similarly modulated wavelengths which are predetrmined dependent upon the relative chrominance of the number ring and the pocket ring of the wheel.