It's the 1990s, and this extremely busy U.S. airport is adding a new concourse -- which means it's also time to upgrade the computers behind the trains that move passengers between terminals, says a pilot fish on the project.

"Each concourse has several door sets to match the number of doors on the train," fish says. "As the train pulls into the station, it must align itself with an antenna on the guideway so that the train's doors and the station doors line up perfectly. Then the station and vehicle doors can open together."

But it's definitely time for an upgrade. When the trains originally started operation in the 1980s, the door controllers were actually run by cheap home computers. A Commodore VIC-20, running a program written in Basic, opened and closed each door set.

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