No transducer is necessary, it is equipped with 32-channel GPS antenna.- Type 1: Speedometer/compass: 0-45 knot speed analogic indication and compass course digital indication (degree by degree).- Type 2: Speedometer/totalizer/compass: speed digital indication 0-999 knots, Km/h or MPH, distance covered up to 99999 miles and compass course (degree by degree).Red and yellow backlit dial.