International Business Machines Corporation

Man F Cheung

James Francis Crossland

Wayne T Comeaux

Robert C Baca

Alex Chliwnyjae

In a magnetic tape drive, a magnetic head simultaneously senses plural track lateral position indicators to generate a like plurality of independently generated sensed position error signals. The sensed position error signals are combined to provide an output position error signal that drives a positioning system to position the magnetic laterally of the length of the magnetic tape. The output position error signal represents an average of the position errors indicated by the sensed position error signals. The quality of the sensed position error signal is monitored, enabling eliminating poor quality signals from the output position error signal for maintaining a quality servo control. If less than a predetermined number of sensed position error signals have acceptable quality, then recording data is prohibited. Independently of sensing servo indicia on a record member to generate the sensed position error signals, a lateral position of the multi-track head is sensed. Upon loading the record member to a load point, the plural track position indicators are simultaneously sensed for centering the head to a predetermined track position. Then, an independent head position sensor is calibrated to the load point track position indicators for use as a verification of validity of the output position error signal. During recording and reading operations, the independent head position is determined on a periodic basis. If an unacceptable change in head position during any measurement period occurs or if the independent measurement indicates an unacceptable lateral deviation from the reference position, all recording is prohibited.

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Tucson, AZ, United States of America

Man F Cheung