Data recovery system having tracking sampling window

Claim 1

For use in recovering data from a memory system including an information storage medium on which data is recorded in serially occurring cells and a transducer for detecting the presence or absence of recorded data in a cell, a data sampling control circuit for producing a windOw which tracks the center of each data cell including: a. ramp generator means in circuit with the transducer for producing a ramp voltage having fixed minimum and maximum voltages and a slope which varies as a function of the frequency at which data is read from the cells; and b. window generator means connected to the output of said ramp generator means and comprising; i. a first voltage threshold detector connected to the output of said ramp generator means for producing a squared voltage waveform having a first level when the ramp voltage is less than the first voltage and a second level when the ramp voltage is greater than the first voltage, ii. a second voltage threshold detector connected to the output of said ramp generator means for producing a squared voltage waveform having a first level when the ramp voltage is greater than the second voltage and a second level while the ramp voltage is less than the second voltage, and iii. logic means for combining the outputs from said first and second voltage threshold detectors to produce a signal which permits sampling only when both squared voltage waveforms are at the second level.