"A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M",
"N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"

BACKBONE. The high-traffic-density connectivity portion of any communications network. In packet-switched networks, a primary forward- direction path traced sequentially through two or more major relay or switching stations. Note: In packet-switched networks, a backbone consists primarily of switches and inter-switch trunks.

BALANCED LINE. A transmission line consisting of two conductors in the presence of ground, capable of being operated in such a way that when the voltages of the two conductors at all transverse planes are equal in magnitude and opposite in polarity with respect to ground, the currents in the two conductors are equal in magnitude and opposite in direction.

BANDWIDTH. The difference between the highest usable frequency of a device (upper frequency limit) and the lowest usable frequency of the device (lower frequency limit) - measured at the half-power points. The difference between the limiting frequencies within which performance of a device, in respect to some characteristic, falls within specified limits. The difference between the limiting frequencies of a continuous frequency band.

BAUD. A measurement of speed based on the number of code elements or units per second.

BINARY DIGIT. A character that represents one of the two digits in the number system that has a radix of two. Either of the digits 0 or 1 that may be used to represent the binary conditions of on or off.

BIT ERROR RATIO (BER): The number of erroneous bits divided by the total number of bits transmitted, received or processed over some stipulated period.

BIT RATE. In a bit stream, the number of bits occurring per unit time, usually expressed in bits per second.

BIT SLIP. In digital transmission, the loss of a bit or bits, caused by variations in the respective clock rates of the transmitting and receiving devices.

BITS PER SECOND (bps, b/s): The number of bits passing a designated point per second.

BLOCK TRANSFER. The process, initiated by a single action, of transferring one or more blocks of data.

BUS. One or more conductors or optical fibers that serve as a common connection for a group of related devices.


BYTE. A sequence of adjacent bits (usually 8) considered as a unit.