A 56k line is a digital connection (possibly a leased line, possibly switched) capable of carrying 56 kilobits per second (kbit/s).
Note that public telephone lines in Canada and the United States cannot carry 56 kbit/s, as CDOC and FCC regulations limit the output power of modems in such a way as to limit throughput to 53 kbit/s, and the practical maximum over real phone lines is closer to 50 kbit/s.
This article (or an earlier version of it) contains material from FOLDOC, used with permission.
