Cable, Network Acronyms, Glossary and Terms
B
Background channel, also called reverse channel: A channel used for
sending data in the opposite direction of the primary (forward) channel. The backward
channel is usually used for sending data at low speeds for control purposes.
Backshell, Hood: A mechanical backing that is sometimes put onto a connector.
The device protects the conductors and can be assembled or injection moulded.
Commonly used with D-Sub connectors.
Balanced circuit: A circuit terminated by a network whose impedance
balances the impedance of the line so that the return losses are negligible.
BALUN: An acronym for BALanced/UNbalanced. A device commonly used to
change one cabling media to another (ex. coaxial to twisted pair balun).
Bandwidth: The information carrying capability of a communication channel
or line.
Bassband: The frequency band occupied by individual information bearing
signals before they are combined with a carrier in the modulation process. In
LANs, one transmitting device at a time on the circuit.
Baseband Transmission: A transmission method where direct current signals
are placed directly onto the transmission medium (cable). Ethernet is a baseband
network type, hence, the "Base" in 10Base-T, etc.
Base group: Twelve communications paths capable of carrying the human
voice on a telephone set. A unit of frequency-division multiple systems bandwidth
allocation.
Baud: Data communications rate unit taken from the
name Baudot. Defined as the number of signal level changes per second regardless
of the information of the information content of those signals.
Baud Rate: A measure of signal changes per second. Commonly used to
rate the speed of a modem.
Baudot: A five level code set named for the early French telegrapher
who invented it. International Telegraph Alphabet (ITA) Number 2 is the formal
name.
Bias: Communications signal distortion with respect to bit timing.
Bit: Binary digital contraction. The smallest unit
of data communication information, used top develop code representations of characters.
Bit-orientated protocol: Refers to those data communications protocols
that move bits across a data link without regard to the meaning of those bits.
Nearly all bit-orientated protocols follow the international HDLC recommendations.
Bit rate: The rate at which those bits (binary digits)
are transmitted over a communications path. Normally expressed in bits per second
(BPS). The bit rate is not to be confused with the data signalling rate (baud)
which measures the rate of signal changes being transmitted.
Bit stream: Refers to a continuous series of bits being transmitted
on a transmission line.
Blank: A condition of "no information" in a data recording
medium or storage location, which can be represented by all spaces or all zeros,
depending on the medium.
Block: Some set of contiguous bits, bytes or both that make up a definable
quantity of information.
Block asynchronous/synchronous transmission: A proprietary software
package for sending asynchronous and synchronous information used primarily by
personal interfaces.
Block check character: A single character appended to the end of a data
block for error checking purposes. The BCC is usually LRC but could also be checksum
results.
Block error rate testing: Testing a data line with groups of information
arranged into transmission blocks for error checking.
Blocking: A condition in a switching system or PABX
in which no paths or circuits are available to complete a call and no dial tone
is returned to the calling party. In this situation there is no alternative but
to hang up and try the call again. Also referred to as a denial or busy condition.
Block multiplexer channel: a computer peripheral multiplexer channel
that interleaves blocks of data. See also byte multiplexer channel. Contrast with
selector channel.
| BNC Connector: |
This refers to the physical form of the connector.
Various suggestions are put forward as to what it stands for, including British
Naval Connection. However, it is a sturdy way to connect and involves a push and
twist due to it bayonet type connectors. They are most suitable for use with RG59/U
cable. |
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Break: A signal to "break in" when the opposite party or unit
is sending. A feature of dial point-to-point teletypewriter systems operating
in half duplex.
Breakout box: A test device utilised for monitoring and inserting signals
in the RS-2332 interface. Bridge equipment techniques used to connect circuits
and equipment to each other ensuring minimum transmission impairment. Bridging
is normally required on multipoint data channels where the drop for the local
loop is separated from the circuit that continues on to the next drop.
Bridge: A networking component that links two or more network segments.
Bridges are used to split busy networks into separate, less congested segments.
Broadband: Refers to transmission facilities whose bandwidth (range
of frequencies that will handle) is greater than that available on voice grade
facilities; sometimes called wideband. Also used to describe a particular kind
of local area network configuration where multiple different users can share the
same cable facility in different channels.
Broadband Transmission: A transmission method where multiple channels
are modulated onto separate carrier frequencies. The result is multiple communications
channels that occupy specific frequency ranges.
Broadcast: The ability to send messages or communicate with many or
all points in a circuit simultaneously.
Burst: A series of events occurring as a group.
Burst error: A series of consecutive errors in data transmission. Refers
to the phenomenon on communications lines where errors are highly prone to occurring
in groups or clusters.
Bus: Also called a "Daisy Chain". A network topology where
each node is connected to one another in line. A major disadvantage is that when
there is a break in the bus the entire network goes down.
Byte: Some set of contiguous bits that make up a discrete item of information.
Bytes are usually 8 bits long.
Byte multiplexor channel: Multiplexer channel that interleaves bytes
of data from different sources. Contrasts with selector channel
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