Details here and here.
Back somewhere after the dinosaurs but before PCs, people interacted with "real" computers through a terminal. The first common terminal was the Teletype (110 baud), and after that, CRT terminals like this one, which were a huge improvement in both speed, and decibels.
As stated on the old-computers.com link above, the ADM-3A was one of the first affordable serial display terminals manufactered by Lear-Siegler, Inc of Anaheim California.
As such it was found almost everywhere that early computers were found from the mid 70s through the 80s.