The principle of rolling over device functioning

Many drivers concerned about rolling back/forward speedometer are interested in the principle of rolling over device functioning. It is well-known that the major device that registers speed and mileage is a speedometer. In its turn, speedometer receives data from speed transducer that operates on the basis of Hall Effect. Hall Effect consists in transformation of mechanical motion into electrical pulse-frequency signal. If instead of speed transducer you will attach a pulsing device, mileage rollup will start. But this principle is not applied to all devices. For instance, there are tools that send digital data by means of CAN directly to an odometer