Abstract: An electronic circuit to be used in conjunction with eddy current non-destructive flaw detection instrumentation for distinguishing from noise or other undesirable signals a flaw signal having a characteristic frequency and a negative excursion followed by a positive excursion. The circuit includes two channels, each of which comprises a threshold detector, a differentiator, a filter, and a variable pulse width one-shot multivibrator, each of which receives the characteristic signal. One channel processes the negative excursion, and the other channel processes the positive excursion. Each channel produces a pulse of predetermined time duration if the excursion being processed exceeds a predetermined threshold. The leading edge of the pulse produced in association with the negative excursion corresponds in time to the time at which the trailing positive going edge of the negative excursion crosses a predetermined negative threshold.