| Term | Definition |
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C Band
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The portion of the frequency spectrum heavily used for satellite and
microwave transmission. 4-6GHz.
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C/I
|
Sinusoidal Interference.
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CAB
|
Configurable Analog Blocks.
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Cable
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A collection of metallic wires surrounded by an insulator through
which an electric current can be passed.
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Cable router
|
Modular chassis-based router optimized for data-over-CATV hybrid
fiber-coaxial (HFC) applications.
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CAE
|
Computer Aided Engineering.
|
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Caller ID
|
A telephone company service allowing the subscriber to view the
phone number and/or name of the calling party on a display device
before answering the phone. Caller ID usually requires some kind of
hardware phone interface to provide the displayed information.
|
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Calling Identity Delivery (CID)
|
Bellcore specification, delivery of the calling number (identity) to
a telephone during the first and second ring.
|
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Calling Identity Delivery on Call Waiting (CIDCW)
|
Bellcore specification, audibly alerting user of a second call
whilst already engaged in the first. BT specification, this term is
technically known as Idle State Signaling but CIDCW is commonly used.
|
|
Calling Line Identity Presentation (CLIP)
|
BT specification, delivery of the calling number (identity) to a
telephone before the first ring.
|
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CAM
|
Content Addressable Memory.
|
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Carrier
|
A continuous signal at a fixed frequency that is capable of being
modulated with a second (information carrying) signal.
|
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Carrier Band
|
The range of frequencies which can be modulated to carry information
on a specific transmission system.
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Carrier Signal
|
A signal which carries no information in and of itself but which can
be modified (by a modem, for example) to carry information.
|
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Carrierless Amplitude Phase (CAP)
|
A type of quadrature amplitude modulation, used for some types of
DSL, that stores pieces of a modulated message signal in memory and
then reassembles the parts in the modulated wave.
|
|
CAS
|
Voice signaling based on bits taken from voice timeslots, used by
many PABXs.
|
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CATV
|
Cable Television.
|
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CBR
|
Constant Bit Rate - One of the five ATM classes of service, which
support the transmission of a continuous bit-stream of information
where traffic such as voice and video, require a constant amount of
bandwidth allocated to a connection for its duration.
|
|
CCIR
|
Committee Consultation International Radiocommunications.
|
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CCTV
|
Closed Circuit Television.
|
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CCU
|
Communications Control Unit.
|
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CDDI
|
Copper distributed data interface.
|
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CDMA
|
Short for Code-Division Multiple Access, a digital cellular
technology that uses spread-spectrum techniques. CDMA does not
assign a specific frequency to each user. Instead, every channel
uses the full available spectrum. Individual conversations are
encoded with a pseudo-random digital sequence.
|
|
CDMA One
|
CDMA One, also written cdmaOne, refers to the original ITU IS-95
(code-division multiple access) wireless interface protocol that was
first standardized in 1993. It is considered a second-generation
(2G) mobile wireless technology.
|
|
CDMA2000
|
CDMA2000, also known as IMT-CDMA Multi-Carrier or IS-136, is a
code-division multiple access (CDMA) version of the IMT-2000
standard developed by the International Telecommunication Union
(ITU). The CDMA2000 standard is third-generation (3-G) mobile
wireless technology.
|
|
CDPD
|
Cellular Digital Packet Data.
|
|
CDVT
|
Cell Delay Variation Tolerance - Used in CBR traffic, it specifies
the acceptable tolerance of the CDV (jitter).
|
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CECL
|
Cascade Emitter-Coupled Logic.
|
|
Cell
|
The 53-byte basic information unit within an ATM network. The user
traffic is segmented into cells at the source and reassembled at the
destination. An ATM cell consists of a 5-byte ATM header and a
48-byte ATM payload, which contains the user data.
|
|
Cellular Radio
|
A method of producing limited area networks where radio frequency
transmission is used to provide the communication channel from
source to destination. The system is normally split into a number of
different "cells" operating at different frequencies. Each receive
and transmit point is also connected by high speed (often 1.544
million bit per second digital T1 circuits) terrestrial lines.
|
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Central Office Interface Circuit (COIC)
|
A device which performs the interface function between the telephone
line and the central office. A COIC sinks current.
|
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Central Processing Unit (CPU)
|
A combination of the logic processor and timing control used as the
basis of a digital computer. Commonly used to mean "computer".
|
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Centralized Processing
|
The method whereby data from various locations is moved to a single
point for computer based processing. The opposite to distributed
processing.
|
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Centrex Service
|
Central exchange service offered by a telephone company supplier.
The switching between "in premises" communications is performed by a
telephone company owned, remote, switch.
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CER
|
Cell Error Rate - A QoS parameter that measures the fraction of
transmitted cells that are erroneous over a specific period of time
(i.e. those that contain errors when they arrive at the
destination).
|
|
CerDIP
|
Ceramic Dual Inline Package.
|
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CERN
|
Conseil EuropÈen pour la Recherche NuclÈaire.
|
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CES
|
Circuit Emulation Service - ATM Forum-defined service that provides
a virtual circuit connection, which emulates the characteristics of
a real, constant-bit-rate, dedicated-bandwidth circuit. Traffic over
ATM networks that comply with the other ATM Forum interoperability
agreements. Specifically, this specification supports emulation of
existing TDM circuits over ATM networks.
|
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CESoP
|
Circuit Emulation Service over Packet - Trunking of TDM data between
two points. Providing a method to transport T1/E1 or T3/E3 streams
over an IP network. The service is the same CES as has been in the
industry for some time, the transport layer is IP which is a new
technology. This is similar to ATM CBR service.
|
|
CF
|
Centre Frequency.
|
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CFB
|
Current Feedback.
|
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Channel
|
A data stream of a given nature mapped over a connection is
considered a channel. For example, a PCM data stream mapped over an
RTP connection would be a single channel, even if that data stream
interleaved more than 1 bearer in each packet. In like manner, any
set of payload types that are all destined to the same HDLC endpoint
would also be considered a channel.
|
|
Channel Bank
|
When used in connection with T1 digital transmission technology
refers to the device that connects equipment such as a PBX to the T1
facility. In a general sense a device that puts many slow speed
signals onto one high speed link and controls the transmissions.
Similar to the combination of a modem and a Multiplexor on an analog
line.
|
|
Channel Insertion Loss
|
For fiber optic links, the static loss of a link between a
transmitter and receiver. It includes the loss of the fiber,
connectors, and splices.
|
|
Channel Timeslot
|
A timeslot allocated to a channel for transmission of a character
signal and possibly in-slot signaling or other information.
|
|
Character
|
A group of bits which is used to represent a "real world" character.
|
|
Character Count
|
An error control method whereby the number of characters in the data
field of a transmission frame is recorded in the transmission frame
header. May also be called byte count.
|
|
Character Signal
|
A set of signal elements representing a character, or in PCM
representing the quantization value of a sample. Note: In PCM, the
term "PCM word" may be used in this sense.
|
|
Character stuffing
|
A technique used to ensure that transmitted control information is
not misinterpreted as data by the receiver during character based
transmission. Special characters are inserted by the transmitter and
then removed by the receiver.
|
|
Characteristic Impedance
|
The termination impedance of a balanced transmission line which will
minimize end to end reflections.
|
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CHBW
|
Channel Bandwidth.
|
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Chroma
|
The NTSC, PAL, or SECAM video signal contains two parts that make up
what you see on the display: the intensity part, and the color part.
Chroma is the color part.
|
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Chroma Demodulator
|
After the NTSC or PAL video signal makes its way through the Y/C
separator, the colors must be decoded. That's what a chroma
demodulator does. It takes the chroma output of the Y/C separator
and recovers two color difference signals (typically I and Q or U
and V). Now, with the luma information and two color difference
signals, the video system can figure out what colors to display.
|
|
Chroma Key
|
This is a method of combining two video images. An example of chroma
keying in action is the nightly news person standing in front of a
giant weather map. In actuality, the person is standing in front of
a blue or green background and their image is mixed with a
computer-generated weather map. This is how it works: a TV camera is
pointed at the person and fed along with the image of the weather
map into a box. Inside the box, a decision is made. Wherever it sees
the blue or green background, it displays the weather map.
Otherwise, it shows the person. So, whenever the person moves
around, the box figures out where he is, and displays the
appropriate image.
|
|
Chroma Trap
|
In a NTSC or PAL video signal, the luma (black and white) and the
chroma (color) information are combined together. If you want to
decode the video signal, the luma and chroma must be separated. The
chroma trap is one method for separating the chroma from the luma,
leaving the luma relatively intact. How does it work? The NTSC or
PAL signal is fed to a trap filter. For all practical purposes, a
trap filter allows certain frequencies to pass through, but not
others. The trap filter is designed with a response to remove the
chroma so that the output of the filter only contains the luma.
Since this trap stops chroma, it's called a chroma trap. The sad
part about all of this is that not only does the filter remove
chroma, it removes luma as well if it exists within the frequencies
where the trap exists. The filter only knows ranges and, depending
on the image, the luma information may overlap the chroma
information. The filter can't tell the difference between the luma
and chroma, so it traps both when they are in the same range. What's
the big deal? Well, you lose luma and this means that the picture is
degraded somewhat. Using a comb filter for a Y/C separator is better
than a chroma trap or chroma bandpass.
|
|
CIR
|
Committed Information Rate - A term used in Frame Relay, which
defines the information rate the network is committed to provide the
user with, under any network conditions.
|
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Circuit Emulation
|
In ATM, a connection over a virtual circuit-based network providing
service to the end users that is indistinguishable from a real
point-to point, fixed-bandwidth circuit.
|
|
Circuit-Switched Network
|
A type of network in which a continuous link is established between
a source and a receiver. Circuit switching is used for voice and
video to ensure that individual parts of a signal are received in
the correct order by the destination site.
|
|
CL
|
Current Loop.
|
|
Cladding
|
The material surrounding the core of a fiber optic cable. The
cladding must have a lower index of refraction than the core in
order to contain the light in the core.
|
|
CLIP
|
Classical IP Over ATM - Encapsulation of IP packets over AAL5 using
LLC and SNAP header to identify the network protocol (in this case
IP) being used.
|
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Clock
|
A term for the source(s) of timing signals used in synchronous
transmission.
|
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CLR
|
Cell Loss Ratio - A QoS parameter that gives the ratio of the lost
cells to the total number of transmitted cells.
|
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CMOS
|
Complementary Metal Oxide Semiconductor - A process that uses both
N- and P-channel devices in a complimentary fashion to achieve small
geometries and low power consumption.
|
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CMRS
|
Commercial Mobile Radio Service.
|
|
CO
|
Central Office - A telephone company facility within which all local
telephone lines terminate and which contains the equipment required
to switch (organize) customer telecommunications traffic
|
|
Coaxial Cable
|
A form of cable where an inner conductor and an outer grounded
shield are positioned about a common axis. This type of cable has
good noise immunity. Coaxial cable is used for digital transmission
up to 100 million bits per second and analog transmission up to 1000
million hertz.
|
|
Codec
|
A device that transforms analog input into a digitally coded output
and transforms digital signals into analog output.
|
|
COFDM
|
Coded Orthogonal Frequency Division Multiplex.
|
|
Color Encoder
|
The color encoder does the exact opposite of the color decoder. It
takes two color difference signals, such as I and Q or U and V, and
combines them into a chroma signal.
|
|
Color Subcarrier
|
The color subcarrier is a signal used to control the color encoder
or color decoder. For (M) NTSC the frequency of the color subcarrier
is about 3.58 MHz and for (B, D, G, H, I) PAL it's about 4.43 MHz.
In the color encoder, a portion of the color subcarrier is used to
create the color burst, while in the color decoder, the color burst
is used to reconstruct a color subcarrier.
|
|
Comb Filter
|
This is another method of performing Y/C separation. A comb filter
is used in place of a chroma bandpass or chroma trap. The comb
filter provides better video quality since it does a better job of
separating the luma from chroma. It reduces the amount of
creepy-crawlies or zipper artifacts. It's called a comb filter
because the frequency response looks like a comb. The important
thing to remember is that the comb filter is a better method for Y/C
separation than chroma bandpass or chroma trap.
|
|
Combined Station
|
A term used in the HDLC data link layer protocol to describe a
station which is either a primary or a secondary station.
|
|
Companding Law
|
Mathematically defined non-linear transfer characteristic used for
Companding. This may be a smooth continuous function or a piecewise
(commonly linear) approximation to a continuous function. The two
com-monly used laws in telecommunications are µ-Law (North America),
A-Law (Europe).
|
|
Component Video Connection
|
The output of a video device (such as a DTV set-top box), or the
input of a DTV receiver or monitor consisting of 3 primary color
signals: red, green, and blue that together convey all necessary
picture information. With current consumer video products, the 3
component signals have been translated into luminance (Y) and two
color difference signals (PP, PR), each on a separate wire.
|
|
Composite Link
|
A circuit carrying composite (multiplexed) data.
|
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Composite Video
|
An analog, encoded video signal (such as NTSC) that includes
vertical and horizontal synchronizing information. Since both
luminance (brightness) and chrominance (color) signals are encoded
together, only a single connection wire is needed (i.e. RCA cables).
|
|
Connection
|
A link between two end-points that is unique through some look-up
method, either through source & destination IP addresses and UDP
ports, through those plus RTP SSRC, and possibly RTP SSRC.
|
|
Connectionless Service
|
Network service where no path can be identified between the
transmitting source and the receiving destination at any point
during a transfer. Datagram packet switched networks provide
connectionless service.
|
|
Connectivity
|
The state which allows the transfer of electrical signals from
source to destination.
|
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Continuously Variable Slope Delta Modulation
|
(CVSD) One of a number of techniques for encoding continuous analog
voice signals into a digital form.
|
|
CPLD
|
Complex Programmable Logic Device.
|
|
Creepy Crawlies
|
Creepy-crawlies refers to a specific image artifact that is a result
of the NTSC system. When the nightly news is on, and a little box
containing a picture appears over the anchorperson's shoulder, or
when some computer-generated text shows up on top of the video clip
being shown, get up close to the TV and check it out. Along the
edges of the box, or along the edges of the text, you'll notice some
jaggies "rolling" up (or down) the picture. That's the
creepy-crawlies. Some people refer to this as zipper because it
looks like one.
|
|
Critical Angle
|
The smallest angle that will completely reflect a ray within a
fiber. The issue of the critical angle relates to why angled
physical contact connectors create a coupling with lower
reflectance.
|
|
Cross Color
|
This occurs when the video decoder incorrectly interprets
high-frequency luma information (brightness) to be chroma
information (color), resulting in color being displayed where it
shouldn't.
|
|
Cross Luma
|
This occurs when the video decoder incorrectly interprets chroma
information (color) to be high-frequency luma information
(brightness).
|
|
Cross Modulation
|
A condition when one signal erroneously modulates another signal.
|
|
Crossbar Switch
|
An early form of matrix switched used by communications suppliers to
implement circuit switching.
|
|
Crossover Cable
|
A twisted pair patch cable wired in such a way as to route the
transmit signals from one piece of equipment to the receive signals
of another piece of equipment, and vice versa.
|
|
Crosspoint
|
The element which actually performs the switching in the telephone
system. Can be digital or analog.
|
|
Crosstalk
|
An unwanted signal induced (picked up) into a conductor as a result
of external electrical activity.
|
|
CRT
|
Cathode Ray Tube.
|
|
CSA
|
Canadian Standards Association - UL's Canadian counterpart.
|
|
CSMA
|
Carrier Sense Multiple Access.
|
|
CTD
|
Cell Transfer Delay - A QoS parameter that measures the average time
for a cell to be transferred from its source to its destination over
a virtual connection (VC). It is the sum of any coding, decoding,
segmentation, reassembly, propagation, processing and queuing
delays.
|
|
CTI
|
Computer-Telephony Integration.
|
|
Customer Premises Equipment (CPE)
|
Any piece of equipment in a communication system that resides within
the home or office. Examples include modems, television set-top
boxes, telephones and televisions.
|
|
Cutback Gamma
|
The coefficient used to scale bandwidth when a long fiber is
shortened.
|
|
CV
|
Constant Voltage.
|
|
Cyclis Redundancy Check (CRC)
|
The CRC is a method of error detection and correction that is
applied to a certain field of data. CRC is an efficient method of
error detection because the odds of erroneously detecting a correct
payload are low.
|
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