64628f99_nical_Details_and_Instructions__Description
[Signal Name] HD IN [Description] 
This is a command from the host machine to the floppy drive, to increase or decrease the amount of power to the read/write heads in case that the high density and double density modes require a different amount of magnetic power, to avoid data corruption between consecutive bits. Also used for differentiating behavior for the inner and outer tracks on the magnetic disk; The inner tracks, just like on a record, are much more compressed in space per bit than the outer tracks are and so magnetic power must be lowered to prevent bleeding to nearby areas.
USB Floppy Disk Drive Converter/Emulator Technical Details and Instructions
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