In the industrial field measurement or measure vehicle speed when the engine speed, outside interference signal is very strong and must take appropriate measures. Can be applied to the industrial site of a speed measurement circuit as shown. By the R2, R3 and C4 form the upper frequency of 1kHz low-pass filter. LM393 comparator powered solely by UDD. UDD through R4, R5 to obtain the reference voltage after divider U1, added to the inverting input of LM393, speed signal U2 is connected with the inverting input. Use of R8, R9, and R6 to the comparator hysteresis voltage is set to 50mV. VD protection circuit prevents the power polarity reversal. VDz for the clamp diodes for protection. For the power supply filter capacitor C2, C3 to denoising capacitance.