US Patent 7248987 Signal processing system for sensor

A signal processing system for a sensor for judging whether an event to be detected has occurred on the basis of a frequency of a sensor output includes a converting device for converting the sensor output into a square wave, a presuming device for presuming whether the frequency of the sensor output is lower than a predetermined frequency referred for judging whether the event to be detected has occurred on the basis of an output from the converting device, and a judging device for judging whether the event to be detected has occurred on the basis of an output from the presuming device.