Vehicle speed signalling using tachometer shaft noise - using noise sensor whose signal is analysed to detect conspicuously strongly occurring frequency

摘要

A method of signalling the speed of a vehicle involves detecting (3) the running noise of the tachometer shaft, coverting it into an electrical signal, analysing it for a conspicuously strongly occuring frequency and forming a signal with a characteristic proportional to that frequency. The electrical signal is filtered to suppress frequencies outside a frequency range including the strongly occurring frequency. USE/ADVANTAGE - Enables derivation of vehicle speed using retrospectively fitted arrangement without significantly altering standard state of vehicle.