Our first internet connection was on ISDN, with a dedicated TA inside the building rented from the Post Office (later Telkom) and a plug in ISA card in one PC that was used as a gateway. We only used one channel, the other had a fax connected to it, as that gave very good connection speeds. Later on when we went to a Diginet link the fax number went back to copper pair using the same line and regular POTS. Was fun for the techs coming into the building to find a 250VDC pair unmarked in the frame, a few got belted by it if not warned, and it took out a few of the test sets as well ( seems they do not like 250VDC fed in to the internals, they glow bright red internally then the set stops working and eventually the smoke comes out of the well sealed case) of the careless.