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German railway seeks IT admin to manage MS-DOS and Windows 3.11 systems
(www.techspot.com)
This is a most excellent place for technology news and articles.
Often these system rely on old components which are just not made anymore.
People don't design every switch, computer and chip themselves. They buy whatever mainstream stuff is available at the time and combine it into a system
If you want to resupply those old parts you literally need to search Ebay to buy some weird outdated 2nd hand MSDOS PC to put in your "awesome reliable railway system".
Upgrading at every new whim is of course bad, but once your system reaches legacy age it's often necessary to fully overhaul and modernize it for the next ~15-20 years.