A circuit for detecting transitions in an alternating signal representing binary information which signal may lack uniform peaks and sharp transitions. The signal is impressed simultaneously on a delay line and a rate of change circuit. A given fraction of the sum of the delayed and undelayed alternating signal is stored in a sample and hold circuit under control of a signal from the rate of change detector. The sample and hold signal and the delayed signal are impressed on a comparator circuit, the output of which is indicative of the binary value of the alternating signal at any given time.