Basic Rate Interface (BRI, 2B+D, 2B1D) or Basic Rate Access is an Integrated Services Digital Network (ISDN) configuration intended primarily for use in subscriber lines similar to those that have long been used for voice-grade telephone service. As such, an ISDN BRI connection can use the existing telephone infrastructure at a business. The BRI configuration provides 2 data (bearer) channels ( B channels) at 64 kbit/s each and 1 control (delta) channel ( D channel) at 16 kbit/s. The B channels are used for

voice The human voice consists of sound made by a human being using the vocal tract, including talking, singing, laughing, crying, screaming, shouting, humming or yelling. The human voice frequency is specifically a part of human sound producti ...

or user

data In the pursuit of knowledge, data (; ) is a collection of discrete values that convey information, describing quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpret ...

, and the D channel is used for any combination of data, control/signaling, and

X.25 X.25 is an ITU-T standard protocol suite for packet-switched data communication in wide area networks (WAN). It was originally defined by the International Telegraph and Telephone Consultative Committee (CCITT, now ITU-T) in a series of drafts a ...

packet networking. The 2 B channels can be aggregated by

channel bonding In computer networking, link aggregation is the combining ( aggregating) of multiple network connections in parallel by any of several methods, in order to increase throughput beyond what a single connection could sustain, to provide redunda ...

providing a total data rate of 128 kbit/s. The BRI ISDN service is commonly installed for

residential A residential area is a land used in which housing predominates, as opposed to industrial and commercial areas. Housing may vary significantly between, and through, residential areas. These include single-family housing, multi-family resi ...

or small business service (ISDN PABX) in many countries. In contrast to the BRI, the Primary Rate Interface (PRI) configuration provides more B channels and operates at a higher

bit rate In telecommunications and computing, bit rate (bitrate or as a variable ''R'') is the number of bits that are conveyed or processed per unit of time. The bit rate is expressed in the unit bit per second (symbol: bit/s), often in conjunction ...

Physical interfaces

The BRI is split in two sections: a) in-house cabling (S/T reference point or S-bus) from the ISDN terminal up to the network termination 1 (NT1) and b) transmission from the NT1 to the central office (U reference point). * The in-house part is defined in I.430 produced by the

International Telecommunication Union The International Telecommunication Union is a specialized agency of the United Nations responsible for many matters related to information and communication technologies. It was established on 17 May 1865 as the International Telegraph Unio ...

(ITU). The S/T-interface ( S₀) uses four wires; one pair for the uplink and another pair for the downlink. It offers a full-duplex mode of operation. The I.430 protocol defines 48-bit packets comprising 16 bits from the B1 channel, 16 bits from B2 channel, 4 bits from the D channel, and 12 bits used for

synchronization Synchronization is the coordination of events to operate a system in unison. For example, the conductor of an orchestra keeps the orchestra synchronized or ''in time''. Systems that operate with all parts in synchrony are said to be synchronou ...

purposes. These packets are sent at a rate of , resulting in a gross

of 192 kbit/s and - giving the data rates listed above - a maximum possible throughput of . The S₀ offers point-to-point or point-to-multipoint operation; Max length: 900m (point-to-point), 300m (point-to-multipoint). * The U_p Interface uses two wires. The gross bit rate is 160 kbit/s; 144 kbit/s throughput, 12 kbit/s sync and 4 kbit/s maintenance. The signals on the U reference point are encoded by two modulation techniques: 2B1Q in North America, Italy and Switzerland, and 4B3T elsewhere. Depending on the applicable cable length, two varieties are implemented, U_pN and U_p0. The U_k0 interface uses one wire pair with echo cancellation for the long last mile cable between the

telephone exchange telephone exchange, telephone switch, or central office is a telecommunications system used in the public switched telephone network (PSTN) or in large enterprises. It interconnects telephone subscriber lines or virtual circuits of digital syste ...

and the

network terminator In electronics, electrical termination is the practice of ending a transmission line with a device that matches the characteristic impedance of the line. Termination prevents signals from reflecting off the end of the transmission line. Reflect ...

. The maximum length of this BRI section is between 4 and 8 km.

External links

*{{cite web, url=http://www.birds-eye.net/definition/b/bri-basic_rate_interface.shtml , title=BRI defined on birds-eye.net , access-date=2012-08-25 , url-status=dead , archive-url=https://web.archive.org/web/20120825163144/http://www.birds-eye.net/definition/b/bri-basic_rate_interface.shtml , archive-date=2012-08-25 Integrated Services Digital Network