- Configuration of a Basic Rate Interface (BRI) line. A
single ISDN circuit divided into two 64 kbps digital
channels for voice or data and one 16 kbps channel for
low speed data ( up to 9,600 baud ) and signaling. 2B+D
is carried on one or two pairs of wires depending on the
interface, same wire pairs that today bring a single
voice circuit into your home or office.
10baseT - 10 Mbps Ethernet LAN technology.
100baseT - 100 Mbps Ethernet LAN technology.
16CIF - 16 times Common Intermediate Format:
1408x1172 pixels. H.263 optional format.
4CIF - 4 times Common Intermediate Format:
704x576 pixels. H.263 optional format.
AAL - ATM Adaptation Layer. Format for sending
packets on a ATM network.
AC signaling - Any
in-band signaling system that uses AC current. The most
common AC signaling system is DTMF. Contrast with DC
Access Device - A gateway to the ATM network. It
provides entry between various hardware and
applications to the device.
Access Provider - Any organization that
arranges for an individual or an organization to have
access to the Internet.
Accunet - Trademark name for high speed
switched digital service provided by AT&T.
ACM - The Association for Computing Machinery
(ACM), founded in 1947, is the largest and oldest
international scientific and industrial computer
society. Through its many Special Interest Groups (SIGs)
the ACM fosters research and communication in a broad
range of computing areas.
A/D - Analog-to-digital.
Pulse Code Modulation (ADPCM) - A
method of sampling and converting analog signals to
digital signals. Similar to DPCM except that when a wide
difference occurs between two successive samples of a
signal, it uses a sophisticated algorithm to code the
ADSL - Asymmetric Digital Subscriber Line.
High bandwidth network technology that transmits at a
higher rate in one direction than the other. Uses
standard POTS wiring for bandwidths up to several Mbps.
AGC - Automatic Gain Control. Algorithm to
normalize volume regardless of speaker's position
relative to microphone.
Aggregation - Method for sending data down two
or more parallel channels.
A-law - European quantizing method for voice
PCM in G.711.
Algorithm - Method for solving a problem or
performing a task.
Analog - The traditional means of sending
traffic over copper wires. Analog signals are
continuously variable, like a flowing line or wave, as
opposed to 1/0 digital signals. Analog signals must be
converted into digital signals in order for computers to
be able to understand them. Used in POTS.
Analog Gateway -
A means of connecting dissimilar
codec's. Incoming digital signal from one type of codec
is decoded by a similar codec and converted to analog.
The Analog signal is then passed to the dissimilar
codec, coded, and decoded at the far end. Analog
gateways achieved interoperability in a nonstandard
environment, but have the disadvantages of degrading
video and audio quality and often reducing
ANI - Automatic Number Identification (ANI) is
a service that provides the receiver of a telephone call
with the number of the calling phone. The method of
providing this information is determined by the service
provider (such as AT&T, MCI, Sprint, and so forth).
ANS - Automatic Noise Suppression. Reduces
background noise from an audio signal.
Annex D - Still-image graphics mode of H.261.
Can support maximum 704x576 resolution.
ANSI - American National Standards Institute.
API - Application Programming Interface.
Protocol (ARP) - Internet
protocol used to map an IP address to a MAC address.
Defined in RFC 826.
Artifact - Coding error found in compressed
audio or video signal.
ARQ/ACF - Admission Request/Confirmation. Used
by a gatekeeper to determine if the endpoint has
permission and resources available, then return the
necessary IP address to connect.
Aspect Ratio - Ratio of horizontal to vertical
picture size. 4:3 for the standard TV. 16:9 for the new
wide screen formats.
Asynchronous - No constant rate. Not
synchronous. A method of data transmission which allows
characters to be sent at irregular intervals by
preceding each character with a start bit and following
it with a stop bit. The timing of the transmission is
not determined by the timing of a previous character.
Applications include communication between most small
computers and mainframes, lower speed transmissions, and
less expensive computer transmission systems.
ATM - Asynchronous Transfer Mode. A connection
oriented service that transmits voice, data, and video
traffic in fixed cell lengths at high speeds into the
gigabit range. A high bandwidth packet-based network
Distribution (ACD) - ACD
directs incoming calls to designated stations in a
specified order of priority.
Autonomous System - Internet
(TCP/IP) terminology for a collection of a gateway
or router that fall under one administrative entity and
cooperate using a common Interior Gateway Protocol.
B channel - 64 kbps bearer channel used for
voice, circuit, or packet switched data.
Backbone - A pathway or cable that joins
multiple computers across small distances ( within the
same building ) or multiple LAN's across long distances.
Bandwidth - The capacity or speed of a
telecommunications transmission medium. example
BAS - Bit-rate Allocation Sequence in H.221.
Capabilities exchange uses these codes.
Baseband - The basic direct output
signal in an intermediate frequency based obtained
directly from a television camera, videoconference
television receiver, or video tape recorder. Baseband
signals can be viewed only on studio monitors. To
display the baseband signal on a conventional television
set a "modulator" is required to convert the
baseband signal to one of the VHF or UHF television
channels which the television set can be tuned to
Baud Rate - The rate of symbols per second (
not the rate of bits per second. )
Bearer service - As defined by CCITT
standards, a type of telecommunication service that
provides the capability for the transmission of
information between user-to-network interfaces.
Bearer services defined for ISDN are circuit mode and
Binary - A system of counting that is base-2.
( The decimal system that we use is base-10.) Unlike the
decimal system which uses digits having possible values
between 0 and 9, the binary system has digits ( bits )
that can only have the values 0 and 1.
B-ISDN - Broadband ISDN. Based on ATM. Can run
up to several hundred Mbps.
Bit - A unit of information that contains one
of two states: on or off. This is the unit of counting
in the binary system.
Bitstream - Data that is transmitted between
systems carrying audio, video, data, and signaling.
Blocking - Artifact found in H.261, H.263 and
MPEG video coding. Picture breaks up into square
sub-sections when the coder cannot produce an accurate
video reproduction due to limited available channel bits
and/or processing power.
Blurring - Artifact found in video when the
high frequencies ( detail ) of the image are not coded.
BONDING protocol - Industry standard B
channel aggregation protocol. Developed by the Bandwidth
on Demand Interoperability Group. Method for making
several BRI lines look like one high-rate line by use of
an IMUX ( Inverse Multiplexer. )
bps - Bits per second. Defining the speed of a
network connection in number of bits transmitted every
BRI - ISDN Basic-Rate Interface consisting of
Bridge ( bridging ) - A data communications
device that connects two or more networks of compatible
protocols. Multipoint Control Unit ( MCU ) that can link
several videoconferencing systems for multipoint calls.
Broadband – A service or network
capable of supporting a wide range of multiple
transmissions (video, data or audio) at the same time.
BRQ/BCF - Bandwidth
Request/Confirmation. Used by a gatekeeper to determine
the bandwidth requested by an endpoint.
Byte – 8 bits to a byte.
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