Abstract: An apparatus for filtering noise from a periodic signal defined by successive occurrences of a first deviation and a second deviation. The apparatus comprises a first delay circuit for imposing a predetermined delay period and a first gate circuit for controlling transmission of the signal, the first gate circuit being operatively connected with the first delay circuit and cooperating with the first delay circuit to delay one of the first deviation and second deviation by the delay period to produce a once-delayed signal. The apparatus further comprises a second delay circuit for imposing the predetermined delay period and a second gate circuit for controlling transmission of the once-delayed signal, the second gate circuit being operatively connected with the first gate circuit and with the second delay circuit and cooperating with the second delay circuit to delay the other of the first deviation and the second deviation by the delay period to produce a twice-delayed signal.