That's likely due to most phone lines not supporting the full 56k speed. In most areas you would be lucky to get 33.6k or 28.8k.
How is that related to phone lines, and not the dial up access point you’re dialing into?
iirc ISDN did require a special phone line, but 56k was fine over regular lines.
How is that related to phone lines, and not the dial up access point you’re dialing into?
iirc ISDN did require a special phone line, but 56k was fine over regular lines.