- A dedicated line is a telecommunications path between two points that is available 24 hours a day for use by a designated user (individual or company). It needs to be connected to the other end for every call or data transfer( i.e modem connection should be established for each data tranfer). It is not shared in common among multiple users as dial-up lines are. A dedicated line can be a physical path owned by the user or rented from a telephone company, in which case it is called a leased line. A synonym is nonswitched line (as opposed to a switched or dial-up line).
- A leased line is a telephone line that has been leased for private use which is connected between end to end always(i.e modems are always connected). In some contexts, it's called a dedicated line because intruding the line will cause immediate disconnection due to improper load termination. A leased line is usually contrasted with a switched line or dial-up line.
Typically, large companies rent leased lines from the telephone message carriers (such as AT&T) to interconnect different geographic locations in their company. The alternative is to buy and maintain their own private lines or, increasingly perhaps, to use the public switched lines with secure message protocols. (This is called tunneling.)