: For basic rate access
in an Integrated Services Digital Network
) environment, a user
reference point that (a) is characterized by a four-wire, 144-kb/s (2B+D) user rate, (b) accommodates the link
access and transport layer
function in the ISDN architecture, (c) is located at the user premises, (d) is distance sensitive to the servicing network terminating equipment, and (e) functions in a manner analogous to that of the Channel Service Units (CSUs) and the Data Service Units (DSUs).
Source: from Federal Standard 1037C