| 摘要 |
A waveform-shaping apparatus for determining engine speed of an automotive vehicle is provided. The apparatus includes a waveform-shaping circuit including a comparator for comparing an input analog signal, alternating in synchronism with rotation of an engine, with a reference signal, so as to produce a binary-coded signal, provided with high and low levels, indicative of the engine speed. A hysteresis providing circuit provides first and second hysteresis components having first and second hysteresis levels to the input analog signal and the reference signal, respectively, to increase a difference in level between the input analog signal and the reference signal so as to mask the influence of noise from interfering with an operation of the waveform shaping circuit. A correcting circuit corrects at least either of the first and second hysteresis levels and time periods during which the first and second hysteresis components are applied, in a preselected relation to a given noise factor.
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