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Technical Glossary B - C

Basic Rate Interface (BRI) - An ISDN service that provides each user with two 64 Kbps bearer(or B(channels for message information and one 16 Kbps(or D(channel for signaling and control over an existing telephone line. Also referred to as 2B+D.

Baud - A unit of signaling speed equivalent to the number of signaling elements per second. Modems that transmit faster than 1800 bps send multiple bits per baud. For example, 9600 bps modems transmit 4 bits per baud.

Bearer Channel - A 64 Kbps channel in Basic Rate and Primary Rate ISDN services used to transmit the customer's voice, data, and video information.

Binary with Eight Zero Suppression (B8ZS) - A technique used with TI 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.

Binary Synchronous Communications (Bisync) - An IBM communications protocol that has become an industry standard. It uses a defined set of control characters and control character sequences for synchronized transmission of binary coded data between stations in a data communications system. Bisync is a byte-oriented protocol.

Bipolar Return to Zero (BRZ) - 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 (BPV) - The occurrence of two successive pulses of the same polarity in a bipolar signal. In T I, this is detected as an error.

Bit - Originally a contraction of "Binary digiT." A bit is the basic unit in data communications and the smallest element of information in the digital system. An individual bit is either a I or a 0. Computer hardware stores and manipulates information by grouping many bits together.

Bit Error Ratio (BER) - The ratio of bits with errors to the total number of bits detected, usually expressed as a number with an exponent to a power of ten. Used to measure the quality of a signal path. Measure of transirfission quality indicating the number of bits incorrectly transmitted in a given bit stream compared to the total number of bits transmitted in a given duration of time.

Bit Robbing - A technique used in Tl multiplexing whereby the least significant bit (bit eight) of each byte in selected frames is "robbed" from use in carrying message information, and instead is used to carry signaling information.

Bps - Bits per second. Indicates the speed at which bits are transmitted across a data connection.

BRI - See Basic Rate Interface.

Bridged tap - Any part of the local loop that is not in the direct transmission path between the CO and the service user.

Byte - A set of eight bits that is used to represent information such as a number, letter, or character.

Cable Binder - Binder used to bundle multiple insulated copper pairs together in the telephone network.

CAP - Carrierless Amplitude & Phase Modulation. A transmission technology for implementing a DSL connection. Transmit and receive signals are modulated into two wide- bands using passband modulation techniques.

CAP - Competitive Access Provider.

CAT5 - Category 5. A level of unshielded twisted-pair wiring performance as defined by EIA/TIA-568.

CBR - Committed Bit Rate.

CCITT - Acronym for the Comite Consultatif Internationale de Telegraphique et Telephonique. It has been renamed the International Telecommunications Union Telecommunications Standards Sector (ITU-TSS).

Cell Relay - Packet switching technique that uses packets of fixed length, resulting in lower processing and higher speeds. Also known as ATM.

CEPT - Conference for European Postal and Telecommunications administrations.

CEU - Commercial End User. See SU, Service User.

Channel - A channel is an independent data path used for full- transmission of customer data

Channel Service Unit (CSU) - The first device encountered by a TI line entering a facility. It protects the equipment beyond it from damage due to disturbances on the T1 line and regenerates the TI signal to meet T1 specifications. A CSU also provides a keep-alive signal to maintain synchronization on the line.

Circuit Switching - A switching method whereby a dedicated path is established between transmitter and receiver.

Clear Channel - A channel in which the entire 64 Kbps of bandwidth is available for customer information. In TI, this requires B8ZS encoding on the line.

CLEC - Competitive Local Exchange Carrier.

Client/Server - A form of distributed computing where the LAN/WAN-based PCs or workstations execute client application software programs, that interact through the network with shared server applications.

ClusterController - A device that controls communications processing for multiple terminals.

CO - Central Office/Central Site. In North America, a CO houses one or more switches to serve local telephone subscribers; known as a public exchange elsewhere.

Codec - A contraction of COder/DECoder. A codec is a device that converts video signals from analog to digital (and vice versa) for data transmission.