Normal telephone lines have a bandwidth of something like 300Hz to 3,500Hz. This may have something to do with the technological constraints of the time that the public switched telephone network was implemented. Apparently, this limits dial-up connection to bulletin board system and the internet to 56kb/s.
If telephone lines were later upgraded to have a bandwidth as wide as 80Hz to 14kHz, or even 20Hz to 20kHz then faster dial-up would be possible.
If telephone lines were later upgraded to have a bandwidth as wide as 80Hz to 14kHz, or even 20Hz to 20kHz then faster dial-up would be possible.