From the XM-6201B manual:
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Function jumper 6:
If in your drive model this jumper is labeled "512/2K", you can change
the data block size from 2kB to 512 bytes (e.g. for use in Unix
systems).
If in your drive model this jumper is labeled "PRV/ALW", you can block
the drive's EJECT button. The disc tray can then only be opened via
software.
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Guess which one I have.... :(
Hey, at least I can prevent unauthorized ejects!