Why must diskettes be erased before duplication?
Diskettes should always be in a magnetically neutral condition before duplication. Erasure has different meanings that can be understood by examining the recording process. Information is written by reversing the direction of a strong magnetic recording field. Longitudinal recording is used for diskettes (except EHD or 4 MB). This means that the magnetic recording field in the head gap, and the induced permanent magnetization in the disk, is always along the track. Two directions of magnetization are allowed; either in the direction of head travel or in the opposite direction. A transition region is created by the reversal and records a binary ONE. Computer disk operating systems and controllers “erase” a disk by deleting files. This only modifies directories and file allocation tables, leaving the format and files intact. Such a diskette is not in a magnetically neutral state and should never be used for high quality duplication. Another hazard of previously recorded disks results fro
