Abstract: A noise blanking circuit for eliminating evidence of noise present in an incoming alternating electrical control signal, such as a shaft encoder or tachometer signal in a servo control circuit, is disclosed. The alternating electrical signal is input to a first input of a shift register having a plurality of outputs. Clock signals having a preselected frequency are input to a second input of the shift register for digitally sampling the alternating electrical signal at the times of occurrence of the clock signals so as to produce digital samples shiftably stored in respective storage locations of the shift register, which are connected to the plurality of outputs of the shift register.

Abstract: A counter for counting pulses or dividing frequencies has a timing signal generator circuit for generating a timing signal at a predetermined interval. A hysteresis circuit has input-output characteristics defining a low input threshold level and a high input threshold level. A control circuit responds to the timing signal for generating at least three control signals having different levels including a first control signal having a level lower than the low input threshold level, a second control signal having a level higher than the high input threshold level, and a third control signal having an intermediate level which is between the low input threshold level and the high input threshold level. The counter has a very large capacity, simple construction, and is effective with both analog and digital signals.