Matt McIrvin's Freaky Alternate Reality

...and even though I worked on printers and knew what a duplex unit was, I still have to do a mental double-take when I hear people talking about "duplex" to mean two-sided printing, because the first thing I think of is still "half-duplex/full-duplex" in the context of early modems and terminals, when it referred to whether the remote end was echoing input or if the terminal should do it locally.