Editing ISDN (section)

=== Basic Rate Interface ===
[[File:ISDN box on wall June 21.jpg|thumb|A decommissioned BT ISDN 2e box]]

The entry level interface to ISDN is the [[Basic Rate Interface]] (BRI), a 128 [[kilobits per second|kbit/s]] service delivered over a pair of standard telephone copper wires.<ref name="Talkers 2013-03-28"/> The {{nowrap|144 kbit/s}} overall payload rate is divided into two {{nowrap|64 kbit/s}} [[bearer channel]]s ([[B channel|'B' channels]]) and one {{nowrap|16 kbit/s}} signaling channel ([[D channel|'D' channel]] or data channel). This is sometimes referred to as 2B+D.<ref name="SW Bell ISDN">{{cite web|title=What is ISDN?|url=http://public.swbell.net/ISDN/overview.html|publisher=Southwestern Bell|access-date=April 6, 2013|archive-url=https://web.archive.org/web/20130415082843/http://public.swbell.net/ISDN/overview.html|archive-date=April 15, 2013|url-status=dead}}</ref>

The interface specifies the following network interfaces:
* The ''[[U interface]]'' is a two-wire interface between the exchange and a ''network terminating unit'', which is usually the [[demarcation point]] in non-North American networks.
* The ''[[T interface]]'' is a serial interface between a computing device and a ''[[terminal adapter]]'', which is the digital equivalent of a modem.
* The ''[[S interface]]'' is a four-wire bus that ISDN consumer devices plug into; the S & T reference points are commonly implemented as a single interface labeled 'S/T' on a [[Network termination 1]] (NT1).
* The ''[[R interface]]'' defines the point between a non-ISDN device and a terminal adapter (TA) which provides translation to and from such a device.

BRI-ISDN is very popular in Europe but is much less common in North America. It is also common in Japan&nbsp;— where it is known as INS64.<ref name="Wisegeek BRI">{{cite web|title=What Is Basic Rate Interface?|url=http://www.wisegeek.com/what-is-basic-rate-interface.htm|access-date=April 6, 2013|archive-date=April 28, 2013|archive-url=https://web.archive.org/web/20130428040354/http://www.wisegeek.com/what-is-basic-rate-interface.htm|url-status=live}}</ref><ref name="ISDN SwitchType">{{cite web|title=ISDN\SwitchType|url=http://msdn.microsoft.com/en-us/library/windows/hardware/ff541725%28v=vs.85%29.aspx|publisher=Microsoft|access-date=April 6, 2013}}</ref>