56 kbit/s line
（重定向自56k line）
A 56 kbit/s line is a digital connection capable of carrying 56 kilobits per second (kbit/s), or 56,000 bit/s, the data rate of a classical single channel digital telephone line in North America. In many urban areas, which have seen wide deployment of faster, cheaper technologies, 56 kbit/s lines are generally considered to be an obsolete technology.