SPEED_ALARM

Published:2009/6/24 4:00:00 Author:May | From:SeekIC

Pulses from the distributor points are pas-sed through a current limiting resistor, rec-tified, and clipped at 4.7 volts. Via Q1 and the diode pump, a dc voltage proportional to engine rpm is presented to RV1; the sharp transfer characteristic of a CM0S gate, assisted by feedback, is used to enable the oscillator formed by the remaining half of the 4011. At the pre-set speed, a nonignorable tone emits from the speaker, and disappears as soon as the speed drops by three or four mph.



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