Patent ID: 7508747

Claim:
An apparatus for detecting the presence of data in a recording media in a plurality of data locations, comprising: (a) a detector associated with the plurality of data locations for sensing one of the data locations and generating an initial signal; (b) a differentiator in electrical communication with the detector for differentiating the initial signal to generate a derivative signal; (c) a first comparator in electrical communication with the differentiator for comparing the derivative signal to a reference signal to determine a zero crossing signal representative of a change in direction of the initial signal; (d) a qualifying circuit in communication with the differentiator for generating a qualified signal from the derivative signal, wherein the qualifying circuit includes an amplitude detector and comparators for generating a positive qualified signal and a negative qualified signal from the derivative signal; and (e) timing circuitry in electrical communication with the first comparator and the qualifying circuit operable to output a data signal only at the occurrence of the negative qualified signal followed by the zero crossing signal followed by the positive qualified signal.