Basic Rate Interface (BRI, 2B+D, 2B1D) or Basic Rate Access is an

Integrated Services Digital Network Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the digitalised circuits of the public switched telephone network. Wo ...

(ISDN) configuration intended primarily for use in

subscriber line In telephony, the local loop (also referred to as the local tail, subscriber line, or in the aggregate as the last mile) is the physical link or circuit that connects from the demarcation point of the customer premises to the edge of the common ...

s 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 channel {{for, Indonesian television network formerly known as B-Channel, RTV (Indonesian TV network) B channel (bearer) is a telecommunications term which refers to the ISDN channel in which the primary data or voice communication is carried. It has a ...

s) at 64 kbit/s each and 1 control (delta) channel (

D channel D channel (delta channel) is a telecommunications term which refers to the ISDN channel in which the control and signalling information is carried. The bit rate In telecommunications and computing, bit rate (bitrate or as a variable ''R ...

) 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 production ...

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

s 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 redundan ...

providing a total data rate of 128 kbit/s. The BRI ISDN service is commonly installed for residential or small business service (ISDN

PABX A business telephone system is a multiline telephone system typically used in business environments, encompassing systems ranging in technology from the key telephone system (KTS) to the private branch exchange (PBX). A business telephone syst ...

) in many countries. In contrast to the BRI, the Primary Rate Interface (PRI) configuration provides more

s 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 w ...

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 Network Termination 1 (NT1) or Network Termination type 1 refers to equipment in an Integrated Services Digital Network (ISDN) that physically and electrically terminates the network at the customer's premises. The NT1 network termination provides ...

(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 In a telecommunications network, a link is a communication channel that connects two or more devices for the purpose of data transmission. The link may be a dedicated physical link or a virtual circuit that uses one or more physical links or shar ...

and another pair for the

downlink In a telecommunications network, a link is a communication channel that connects two or more devices for the purpose of data transmission. The link may be a dedicated physical link or a virtual circuit that uses one or more physical links or shar ...

. It offers a full-duplex mode of operation. The I.430 protocol defines 48-bit

packet Packet may refer to: * A small container or pouch ** Packet (container), a small single use container ** Cigarette packet ** Sugar packet * Network packet, a formatted unit of data carried by a packet-mode computer network * Packet radio, a form ...

s comprising 16

bit The bit is the most basic unit of information in computing and digital communications. The name is a portmanteau of binary digit. The bit represents a logical state with one of two possible values. These values are most commonly represented a ...

s from the B1 channel, 16 bits from B2 channel, 4 bits from the D channel, and 12 bits used for synchronization 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 Echo suppression and echo cancellation are methods used in telephony to improve voice quality by preventing echo from being created or removing it after it is already present. In addition to improving subjective audio quality, echo suppression ...

for the long

last mile Last mile may refer to: * Last mile (telecommunications), the final leg of the telecommunications networks that deliver services to retail end-users * Last mile (transportation), the final leg the movement of people and goods from a transportation ...

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