64628f99_nical_Details_and_Instructions__Description
[Signal Name] DS0, DS1, DS2, DS3 [Description] 
The DISK SELECT signal, identical to the DRIVEA/DRIVEB but which are on physically different electrical lines. This is more popular overseas and may have four floppy drives on the same ribbon cable, instead of two, although this is rarely done. Many PCs use this type of drive anyways, because the DS1 setting is identical to the DRIVE B setting.
USB Floppy Disk Drive Converter/Emulator Technical Details and Instructions
Description