A 56 kbit/s 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 was originally based on material from the Free On_line Dictionary of Computing, which is licensed under the GFDL.
A 56 kbit/sline is a digital connection (possibly a leased line, possibly switched) capable of carrying 56 kilobits per second (kbit/s), the data rate of a normal single channel digital telephone line in North America.
With the wide deployment of faster, cheaper, technologies such as ADSL and SDSL, 56 kbit/slines are generally considered to be an obsolescent technology.
The figure of 56 kbit/s is derived from its implementation using the same digital infrastructure used since the 1960s for digital telephony in the PSTN, which uses a PCM sampling rate of 8000 Hz used with 8-bit sample encoding to encode analogue signals into a digital stream of 64000 bit/s.
A 56k leased line is a type of digital leased line, available from your local phone company and similar to a T1 line, which is capable of carrying digital data between two remote locations at a fixed transmit and receive speed of 56,000 bps.
One major reason why 56kmodems rarely live up to their name is because they are designed to extract every spare ounce of speed possible from lines that do not efficiently carry digital data, and were once thought to be fundamentally incapable of anything faster than 9600 bps.
As the phone line is provisioned by the telco to be used for digital data, there is no bandwidth expended compensating for telco equipment mistakenly "improving" the signal for the human ear, nor are complex protocols and algorithms required to probe the line condition and recover from distortion.
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