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Glossary of broadband terminology: B

B Channel: The "bearer" channel, in the ISDN scheme. With both basic rate and primary rate ISDN, this is a full-duplex 64 Kbps channel for sending and receiving data. See also Basic Rate Interface, Integrated Services Digital Network, and Primary Rate Interface.
Backbone: That part of a network which is used as the main path for carrying traffic between network endpoints.
Backbone LAN: A transmission facility designed to interconnect two or more LAN segments.
Backplane: A common bus in a chassis that distributes low voltage power to each card slot.
Bandwidth: This is a reflection of the size or the capacity of a given transmission channel.
Baseband: Using the entire bandwidth of a transmission medium, such as copper cable, to carry a single digital data signal. Note that this limits such transmission to a single form of data transmission, since digital signals are not modulated. See also Broadband.
Basic Encoding Rate: Bit error rate, or the ratio of received bits that are in error; also, a rule for encoding data units described in ANSI. See Bit Error Rate Test.
Basic Rate Access: See Basic Rate Interface.
Basic Rate Interface: This is an ISDN interface typically used by smaller sites and customers. This interface consists of a single 16 Kbps data (or"D") channel plus two bearer (or "B") channels for voice and/or data. Also known as Basic Rate Access, or BRA.
Baud: Transmission rate of a multilevel-coded system when symbols replace multiple bits. Baud rate is always less than bit rate in such systems.
Bearer Channel: A 64 Kbps channel in basic rate and primary rate services of ISDN used for customer message exchange. See also Basic Rate Interface, Integrated Services Digital Network, and Primary Rate Interface.
Binary Eight Zero Suppression: A technique in T-1 that modifies the AMI encoding to ensure minimum pulse density without altering customer data.When eight zeros in a row are detected, a pattern with intentional bipolar violations is substituted. These violations enable the receiving end to detect the pattern and replace the zeros.
Binder Group: Cable pairs are typically arranged under the cable sheath in binder groups. The binder is a spirally wound colored thread or plastic ribbon used to separate and identify cable pairs by means of color-coding.The enclosed pair group is called a binder group. The groups are composed of insulated twisted copper pairs that are also twisted within each binder.Typically they are wrapped in 25 pair bundles. For example, pairs 1-25 might be in one binder group and pairs 26-50 in another. In xDSL, one often hears discussions of signal interference between adjacent pairs within a binder group. The best of all worlds is to keep a data pair separated from another data pair by assigning it to an adjacent bindergroup. If the data pairs are too close to each other they create what telcos call "disturbers" (i.e., crosstalk). If a "disturber" exists in the binder group serving your SNI, NID, MPOE, etc., you may not "qualify" for DSL service.
Bipolar Return to Zero: A bipolar signal in which each pulse returns to zero amplitude before its time period ends. This prevents the buildup of DC current on the signal line.
Bipolar Violation: The occurrence of two successive pulses of the same polarity in a bipolar signal. In T-1 it is detected as an error.
Bit: A contraction of "binary digit." A bit is the smallest element of information in the digital system.
Bit Error Rate Test: A test that reflects the ratio of errored bits to the total number transmitted. Usually shown in exponential form (10^6) to indicate that one out of a certain number of bits are in error.
Bit Robbing: A technique in T-1 multiplexing in which the least significant bit (bit 8) of each byte in selected frames is robbed from being used to carry message information and instead is used to carry signaling information.
Bits Per Second: The raw data rate of a system.
Bridge Tap: A sometimes-accidental connection of another local loop to the primary local loop. Generally it behaves as an open circuit at DC, but becomes a transmission line stub with adverse effects at high frequency.It is generally harmful to DSL connections and should be removed. Extra phone wiring within one's house is a combination of short bridge taps. A POTS splitter isolates the house wiring and provides a direct path for the DSL signal to pass unimpaired to the ATU-R modem.
Broadband: Sharing the bandwidth of a medium such as copper or fiber optic cable, to carry more than one signal -- allowing the integration of voice, video, and data over a single transmission medium; VDSL is a broadband transmission scheme, for instance.
Broadband Integrated Services Digital Network: A technology suite designed for high-bandwidth multimedia applications and the integration ofvoice, data, and video. The two transmission types are ATM and STM.
Brouter: A device that can provide the functions of a bridge, router, or both concurrently; a brouter can route one or more protocols, such asTCP/IP and/or XNS, and bridge all other traffic.
Bus Networks: A bus network is a multiple access medium for small networks and usually only consists of one cable and the devices that are attached to it.