In the middle of the 1970’s they made modems with rubber cups so that you could plug your phone handset into it. We didn’t have a LAN in the office. Each terminal (NOT A PC!) would plug into the modem. Every office had an extra telephone just for the terminal connection. Using this we could logon to our mainframe time sharing accounts where we did our work.
Yep it just the old acoustically coupled modem without the rubber cups