Abstract: A read back circuit for recovering digital data stored on a magnetic storage medium as a series of sequential magnetic flux transitions comprises first means for providing a read signal indicative of magnetic flux transitions on the medium and second means operatively coupled to the first means for providing a differentiated read signal having zero crossings indicative of peaks in the read signal. A third means is operatively coupled to the second means for normally applying an offset to the differentiated read signal and for temporarily removing the offset during the occurrence of peaks in the read signal, thereby preventing erroneous zero crossings of the differentiated read signal.