alt Hacker NewsThe clue is in the rs232 mentioned in my comment. Linux is a Unix, even if nobody does it today you can configure an external terminal via serial port and use the system as if you were a user.
The two Linux box were one with the modem and the other via Nat (Ethernet but with old coaxial cables). The AT was just a terminal.
Having a serial terminal was just good fun, too, back in the days when having multiple monitors / computers wasn't common. I ran Slackware on a 486 w/ X Windows so I could use Netscape Navigator and I had an old RS-232 dumb terminal from my dad's old computer connected so I could have a shell open w/ an IRC client or my mail while I used Netscape. (I never liked running Pine in an X terminal. It was abnormal and strange. It seemed more natural on the terminal and it was cool to have two screens!)