@sabi My first modem was a a used decommissioned military modem in a grey 19" enclosure about 15 cm high. Rock solid and quite heavy, with a large printed circuit board filled with discrete electronics and lots of coils. I bought it around 1976 for 200 Dutch guilders and used it with a (borrowed) ADM-3A terminal to dial from home into the university's PDP11/45 running Bell Labs UNIX 6th Edition.