Control PanelInApple computer operating systems, a collection of utilities, accessible through the Apple Menu, that provides access to many basic operating parameters, including sound, m
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continuous wave Awave that is constant or
unvary-ing in its major characteristics, such as amplitude
continuous wave transmissions Any transmissions
technology that employs continuous signals rather
than pulses Since most communications media rely
on pulses or modulation to send meaningful
informa-tion, continuous wave transmission is more
special-ized and generally used in signaling situations, such
as security systems, in which an interruption of the
continuous wave serves as an alert or system startup
signal
control field In many types of data communications
that employ fields as information units, a control field
is assigned to contain information about how to
pro-cess related data
control panel A console used to control operations
of a system, vehicle, aircraft, or network The
con-trol panel may consist of physical switches or dials
or may be a text or graphical interface on a computer
screen (often simulating switches and dials)
Control PanelInApple computer operating systems,
a collection of utilities, accessible through the Apple
Menu, that provides access to many basic operating
parameters, including sound, memory, monitor
set-tings, network configuration setset-tings, etc
control segment In the Global Positioning System
(GPS), the control segment is a global network of
control and monitoring stations that ensure the
accu-racy of satellite positions and their clocks This
co-ordination is an important part of GPS, as the data is
derived in part from the relationship of the satellites
to one another and their signals See atomic clock
control terminal Aworkstation or personal computer
configured to provide control of a network from any
routing node It acts as a command input and display
console Through remote access commands, it is
pos-sible to control a network from a node other than the
one that is physically connected to the terminal
(vir-tual terminal)
controlled access unit CAU In the generic sense, a
device in a link that selectively controls the entry and!
or exit of people, things, or data to a system A door
with a lock is a simple example of a physical CAU
A revolving entry gate at a circus, with security
per-sonnel and ticket sellers, is another access unit in that
people are funneled through a specific physical
lo-cation A firewall is an example of a computer
net-work CAU in the sense that it controls access to or
from the system behind the firewall See Controlled
Access Unit
Controlled Access Unit When spelled with capitals,
a CAU more specifically refers to an active wiring
concentrator used in Token-Ring networks The CAU
transforms the logical ring topology into a star
topol-ogy, for example, to facilitate installation in larger
building environments Two or more CAUs can be
interconnected to produce a segmented network
Multiple CAUs intercommunicate through the main
ring path The CAU provides a means to attach units
to the ring network as though it were a star topology,
while still maintaining the basic ring configuration
for the network traffic logic However, it is more robust
(more tolerant of a bad unit on the system) and more flexible (accommodating additional computers) than
a basic ring network See Lobe Attachment Module, Multistation Access Unit, Token-Ring network Controller Area Network CAN A multimaster se-rial network bus originally developed for controller circuits in the automotive industry by Robert Bosch GmbH, Germany, in 1986 CAN is now being adapted for marine, medical, industrial, and other control and automation applications The CAN bus
is a high-speed (up to I Mbps), half duplex network communicating among microcontrollers It is capable
of interconnecting over 2000 devices and is often used in imbedded systems It is particularly useful for short messages
Data in a CAN system are transmitted and received using Message Frames Standard CAN uses II-bit identifiers, Extended CAN uses 29-bit identifiers There are two ISO standards for CAN, specified for two different speeds See CAN in Automation controller A software-supported computer hardware device that works in conjunction with the operating system, through the various system interfaces, han-dling input and output and control of that device Thus, a disk controller provides functions to handle
a hard drive The most common desktop computer disk controllers follow SCSI and IDE standards SCSI controllers are also commonly used for scanners, CD-ROM drives, and many types of cartridge drives A serial controller handles serial communications into and out of the computer, usually to a printer or mo-dem RS-232 and RS-423 are two of the most com-mon desktop serial interface standards
When a computer first boots up, one of the processes that occurs is bringing the controller hardware and software online The computer needs to locate the various devices and will often load a variety of soft-ware device drivers that support the hardsoft-ware func-tions See controller card
Controller Area Network CAN A multimaster-ca-pable serial bus system that facilitates the network-ing of intelligent devices, includnetwork-ing sensors and ac-tuators CAN is associated with the lowest layers of the ISO/OSI reference model
controller card A computer circuit board card that connects through a slot (e.g., PCI), to provide an elec-trical and logical connection between a device and the main circuitry of the computer There are a lim-ited number of slots available for controller cards, usually more in a tower model, and extra power may
be needed to handle the extra load There may be jumpers or dip switches on the controller card to fine tune the settings, as on a graphics card or hard drive controller The communications standard used by the controller card must fit that of the slot into which it
is inserted An EISA card call1iot be put in a PCI slot, and vice versa Software may need to be loaded onto the computer for the operating system to recognize the controller card functions See controller CONUS Contiguous United States Adesignation for the continental, contiguous U.S consisting of 48 states The term is used when referring to U.S travel,
Trang 2converterA very broad term for anything that
changes the incoming signal to a different outgoing
signal or that converts one type of physical
connec-tion to another Converters are frequently used to
con-vert between alternating current (AC) and direct
cur-rent (DC) or to convert one cable type to another A
converter may be used to convert a frequency
spec-trum from one range to another, but this is pushing
the boundaries of the tenn, as converter usually
im-plies fairly simple conversions More complex ones
tend to have their own descriptive tenns When a
con-verter is used simply to change one type of plug or
jack into another without any electrical changes, it is
more commonly called an adapter When it simply
links two components with no changes in the signals,
it is called a connector.
convexSmoothly protruding and curving outwards,
like the outside surface of a bowl A continuous or
mostly continuous surface that follows the outer
sur-face of a spherical/elliptical shape The tenn is
gen-erally applied to surfaces that do not constitute a full
sphere Thus, the outer surface ofa ball is considered
spherical, but if it were chopped in half or less than
half, the smaller portion would be considered
con-vex, whereas the larger portion, while still being
pri-marily convex in geometry, tends to be semantically
called spherical rather than convex
If an elongated, rounded-end lozenge-shaped object
like a vitamin pill were cut exactly in half between
the two rounded ends, the portion that curves toward
the midsection would be considered convex, but the
portion where the curve straightens out to include the
straight midsection of the pill would not The outer
surfaces ofmany lenses are convex as are the "back"
surface ofparabolic antennas Contrast with concave
Conway's lawThis saying has been variously
re-stated (and probably improved over time) The idea
is that there is congruency between the composition
of the software team and the final design of the
soft-ware (and in this version, an implied dig that a single
programmer wouldn't ever finish the project), stated
as, "Ifyou assignnpersons to write a compiler, you'll
get ann-Jpass compiler." Another version, not quite
as apropos to computereze as the one just stated, but
perhaps closer to the original, is "If you assign four
groups to working on a compiler, you'll get a 4-pass
compiler."Itis attributed to Melvin Conway, an early
Burroughs computer programmer
Another Conway's law has been stated in Dilbertian
fashion as follows, "There is always one person who
knows what is going on That person must be fired."
Cook, GordonAuthor of the Cook Report on
Inter-net,a newsletter devoted to issues concerning the
commercialization and privatization of the Internet
Cook was formerly science editor at the John von
Neumann National Supercomputer Center Later he
served for 18 months as a director for the U.S
Con-gress Office ofTechnology Assessment, assessing the
National Research and Education Network (NREN)
Cook Report on InternetAn independent,
opinion-oriented by-subscription monthly online newsletter
nology The publication monitors telephony and com-puter convergence and new technologies being adapted by forward-thinking telecommunications providers
Cooke, William Fothergill(1806-1879) A British researcher who collaborated with Charles Wheatstone
in developing the telegraph The two met in 1837 at
a time when both were researching similar telegraph technologies See telegraph history; Ronalds, Francis;
Wheatstone, Charles
cookieAtoken or other transaction acknowledgment
orillpassed between transacting processes or pro-grams to keep a record of an access or action Cook-ies may be passed transparently between systems as part of nonnal operational protocols
Data cookies are an integral part of Internet com-merce, especially in the fonn of identifiers in Web link referrals and shopping cart purchases made online Cookies can be passed from the~rowserto the shopping cart site to identify the visitor for later purchasing or statistical purposes and mayor may not
be acknowledged with infonnation from the vendor being deposited on the buyer's system The cookie may also track customers as they browse other sites (common on the Internet) and then return to finish their online shopping Some people object to these types of cookies, which are automatically offered to the visited site by the browser and will disable this
capability, and many people have objected to the re-verse cookie,one that is deposited on the visiting browser's system, often without the knowledge ofthe user, as this opens a porthole for viruses, vandalism, and unfair trade practices See Callerill
cookie monsterAninvasive software program, widely distributed in the mid-1980s, named for the popular children's television program character The program would prompt the user with "Give me cookie ." at increasingly shorter intervals, gradually taking
up more and more CPU time, and if the user didn't type the word "cookie" it would eventually print so frequently, and steal so much CPU time, that it would make the terminal unusable The original was ru-mored to have come from MIT See virus
Cooperative Research Action For Technology
CRAFT One of a number of programs of the Euro-pean Union, CRAFT is a means to enable small- and medium-sized enterprises (SMEs) to engage third parties to carry out research on their behalf The third parties may be commercial research organizations or research departments of academic organizations In
a CRAFT project, the SMEs are made up of at least three participants from at least two different EU states and the area ofresearch must fall within the umbrella
of the RTD Framework Programme which can
in-clude software development, for example
Coordinated Universal Time, Temps Universal CoordonneUTC.Aninternational astronomical time reference devised in 1970 by the lTV UTC is related
to the Greenwich meridian, that is 0 degrees longi-tude on the Earth's surface
UTC uses a 24-hour clock, thus, 2:00pm is 1400 hours
~~.~'
.; ' :~.
.V,·
Trang 3Fiber Optics Illustrated Dictionary
Since UTC cannot exactly match Earth's slightly
varying rotation, UTC was set to a UT 1 reference
with the Earth's position as of0000 hours on 1
Janu-ary 1958 Deviations are adjusted with leap seconds
Coordinated Universal Time is based upon the
aver-age period of the rotation around the Sun UTC
re-ceives its frequency and time information from over
50 centers around the world and broadcasts it over a
number of radio frequencies, with tones to indicate
seconds and spoken words for upcoming minutes
copper Amalleable, metallic chemical element with
high conductivity, which makes it invaluable in the
manufacture of electrical wire and heating
imple-ments It is the most widely used conductor in
elec-trical work due to its properties, availability, and
price Gold and silver are also good conductors but
not economically practical for most electrical work
Copper Distributed Data Interface COOL An
ANSI standard version ofFiber Distributed Data
In-terface (FDDI) that runs on twisted-pair copper
wir-ing rather than on optical fiber
copper twisted pair Copper is very commonly used
for electrical wires, and twisting two copper wires
to-gether can improve its transmission properties Apair
of wires is intertwined in a helical pattern over
tance in order to reduce capacitance Over longer
dis-tances, the distributed capacitance can build up, and
load coils are introduced, at intervals, to help balance
capacitance and inductance The use ofload coils for
telephone voice connections is common; however,
they can cause problems when the same wires are
used for data transmission Copper pairs used for data
transmission may be constructed differently from
voice lines, with the insertion ofa metal screen to
dif-ferentiate the transmit and receive
Compared to fiber optic cable, it is very easy to
con-nect twisted pair Cutting and splicing is relatively
straightfolWard, whereas the cutting and splicing of
fiber optic must be done with great care so as not to
alter the alignment properties of the optic
wave-guides
Sometimes the twisted pairs are further aggregated
into binders, a group of 25 twisted pairs This
sim-plifies installation in multiconnection installations
Color coding is often used to keep track of the
con-nections and binder bundles See copper wire, load
coils See twisted-pair wire for a diagram
copper wire The most commonly used transmissions
medium for telephone calls and related
telecommu-nications Copper wires were first widely installed in
the 1880s, superseding some of the earliest
galva-nized wires used for telegraph signals Copper wire
with an iron core was developed by Bell's Thomas
B Doolittle in 1883, and it became popular due to
its combination of conductivity and durability
Copper wire for phone communications was most
commonly installed as a single wire, strung on
util-ity poles, or as twisted pair More recently, gel-filled
multicables comprising up to almost 5000 twisted
pairs have been used where many connections are
required
Many bare conducting wires have been strung
with-out insulation, but insulation is often used to protect the wire from damage, interference, and corrosion Rubber, gutta-percha, latex, plastic, and wound pa-per have all been used as wire insulators, as have air and jelly inside an outer core See coaxial cable, cop-per twisted-pair, CoppelWeld, fiber optic
Copperweld A trademark name for an early
combi-nation of copper wire with an iron core It combined the flexibility and conductivity of copper with the durability of iron and increased the longevity of the wires
coprocessor A computer processor that is not
con-sidered the main or central processing unit (CPU) but assists the CPU in handling heavier processing loads
or specialized processing loads CPUs are designed
as general-purpose chips, and are not intended spe-cifically for anyone type of task The Amiga com-puter, released in 1985, is an example of one of the first desktop computers to make extensive use of coprocessing chips to handle resource-hungry graph-ics and video operations in order to prevent these computations from slowing down the CPU This ar-rangement is now more common
The interaction ofa CPU with support circuitry such
as coprocessors is one of the reasons the raw speed
of the CPU is not a perfect indicator of the perfor-mance of a system Computers with coprocessing chips and average speed CPUs have often been shown
to outperform faster CPUs if they don't have coprocessing support Coprocessor chips are gradu-ally becoming more common in desktop systems, with math coprocessors becoming prevalent in the 1980s, and graphics and sound coprocessors beginning
to show up in many consumer systems in the 1990s
COPS See Common Open Policy Service Protocol COPT Coin-Operated Pay Telephone.
copyright Certain legal safeguards conferred by
gov-ernment agencies Copyright protections are granted
to original works for a specified period of time, de-pending upon the type of work Original drawings, musical compositions, software programs, and sto-ries are copyrightable Inventions are sometimes copyrightable, sometimes patentable, and sometimes both It is important to include a copyright symbol© and a date with the name of the copyright holder, or
the word copyright and the date, on each
presenta-tion ofthe original work or reproducpresenta-tion thereof The
C with the circle is recognized internationally by those countries cooperating in international copyright treaties, such as the Berne Convention
Afee-based fonnal copyright process is available in most countries to provide a record ofthe type and date
of the copyright materials This record is a good source of evidence in a legal dispute, but the copy-right registrar does not police the copycopy-right; that is the responsibility of the copyright holder
Many researchers, academics, and business employ-ees are mistakenly under the impression that they automatically own the copyright for something they create This is often not true, although the laws have swung slightly more in the direction of the creator in recent years However, if it is work for hire or work
Trang 4ties, the educational institution or the corporation
usuallyowns the copyright to the work, unless there
is a specific written agreement stating otherwise If
the employee, on the other hand, creates some
origi-nal work outside of working hours and canprove it
wasn't done under the direction of or using the
re-sources of the employer, the employee may have a
case for copyright ownership
Copyright does not protect the owner if someone
in-dependently comes up with the same idea and has not
copied the original idea However, it can be difficult
to prove the idea was conceived independently, if it
is very similar to another, and that proofmay be
nec-essary in court ifa legal proceeding is initiated Most
public libraries have excellent references on
copy-right requirements and registration guidelines, as do
all U.S government documents repositories See
in-tellectual property, patent, trademark
CORBACommon Object Request Broker
Architec-ture.Inthe current state ofcomputing, there are many
different vendors, many different computer platforms,
and many different software applications, resulting
in much duplication and incompatibility Now that
we have the Internet as a common ground for
shar-ing development strategies, applications, and
appli-cation-development tools, it is not necessary for these
incompatibilities to exist, and neither is it necessary
for a consumer to be forced to use anyone particular
computer platform
CORBA is a strategy and a set oftools It enables
re-usable programming objects to be used by many
ap-plications in a platform-independent manner.Itis the
combined effort ofmore than 500 vendors, engineers,
and end users, organized as the Object Management
Group (OMG) CORBA is a set of specifications for
platform-independent, interoperable, distributed
ob-ject-oriented applications By using CORBA
speci-fications, software vendors can create truly global
software that can be distributed over the Internet and
run on a multitude of systems
CORBA is an infrastructure that provides general
services, and request and response capabilities at a
low level The distribution ofobjects written in a
va-riety of programming languages is supported
CORBA does not define the upper level architecture;
this decision is left to individual developers See
Ob-ject Request Broker
cord lampInmanual switchboards, or any type of
cord panel where indicators are used, the lamp is a
small bulb associated with a physical socket
connec-tion for a cord jack that lights up ifthe associated
cir-cuit is active Cord lamps were used on old telephone
switchboards to signal active switches The modem
equivalent is an indicator light on a multiline
tele-phone console
cordboardAhistoric switching panel,
human-oper-ated with long cloth-wound patch cords which
plugged into jack receptacles on the desk level and
interconnected, as needed, with jack receptacles on
the wall corresponding to the local phone desk See
switchboard
are used in wireless systems, acordless switchboard
is not a new wireless technology, but rather an older switching technology in which human operators used keys instead of patchcords to connect call circuits While this was a great improvement over patchcords and was still used on many long-distance circuits until the 1970s, it was slow and expensive compared to all-electronic automatic switching systems
cordless telephoneAbattery-powered wireless tele-phone handset with a short antenna and a separate charging element and AC adaptor, usually using very short-range radio signals While a cellular phone is a type ofcordless phone, the phrasecordless telephone
is usually used to refer to very short-range phones used within buildings or circumscribed areas Cordless phones are predominantly analog, but more digital phones are being produced, resulting in more options for interfacing with a computer or providing secure or semisecure communications
core1 Center, inner, inmost 2 A central strand or wire around which other conductive or protective lay-ers, strands, or insulating materials may be wound Usually the main conducting portion ofa wire assem-bly In most electrical installations, copper wire is used as a conductive core In fiber optic cable, the core glass is usually surrounded by a layer of lower refractive cladding glass See cladding 3 A central bar, often of iron, around which a coil is wound to create an electromagnetic part See armature, coil, electromagnet 4 A small doughnut-shaped magnetic component used for computer storage, with polarity representing binary states See core dump 5 A cen-tral, removable strand around which other materials may be wound or braided in order to provide a brace for molding their shape
Core, the 3D Core Graphics System A baseline specification developed in the mid-1970s to encour-age standards for device-independent graphics This specification led to development of the Graphical Kernel System (GKS), an official standard for 2D graphics For 3D graphics, GKS-3D and the Programmer's Hierarchical Interactive Graphics Sys-tem (PRIGS) became official standards in the late 1980s
core diameterA description of the thickness of an inner, usually conducting material, as ofcopper wire
or the inner lightguiding core in a fiber optic cable
as measured in cross-section through the center perpendularto the axis ofthe length ofthe cable See American Wire Gauge, Binnington Wire Gauge
core dumpA copy of the contents of core memory from a process error condition, usually consisting of undecipherable symbols and unprintables that can make a terminal or printer go crazy On large systems, the output can be voluminous Irate receivers ofspam, unsolicited commercial email, have been known to retaliate by sending back large core dumps
core to cladding offsetSee concentricity error
core-to-core splicerAn industrial fusion splicing device for joining fiber optic cables A core-to-core splicer allows active alignment in three axes, compared
Trang 5Fiber Optics Illustrated Dictionary
to two-axis cladding alignment splicers A
core-to-core splicer provides alignment ofsingle-mode,
mul-timode, and active fiber cores and may include a
built-in thennal sleeve shrbuilt-inkbuilt-ing mechanism A splice log
memory or computer link may be provided for
keep-ing a record of splices and their statistics Since this
type ofsplicer may be portable, for field work, it may
also include a pigtail port for facilitating cable
ter-mination and may have a built-in cleaver See
clad-ding alignment splicer, fusion splicer
Cornell, Ezra (1807-1874) Cornell was talented in
both business and mechanics and was associated
closely with Samuel Morse and Hiram Sibley,
founder ofthe company that became Western Union
Cornell contributed to early telegraph installations
and helped Morse construct the historic Washington,
D.C to Baltimore, MD line that was funded through
the U.S Congress Cornell designed early insulators
from glass plates Cornell remained a lifetime
direc-tor of Western Union and was the chief founder of
Cornell University
corner reflector In its simplest fonn, two
intersect-ing or joinintersect-ing flat reflective surfaces with sufficient
angle between them (usually 20 to 160 degrees, and
often 90 degrees on the reflective side) to allow
re-flectance ofa beam The comer may also be in three
planes, shaped like the comer of a room where the
walls join the floor or ceiling Comer reflectors are
common in radar applications The materials vary, but
mirrored glass and metals are often used
corner reflector antenna A type of antenna which
combines a primary radiating element in relation to
two angled metallic surfaces, or rods arranged in a
plane Various styles of comer reflectors are used in
UHF television reception and radar applications
Corning Cable Systems A leading global
manufac-turer ofcopper and fiber optic communications
prod-ucts for voice, data, and video network applications
Coming Cable is wholly owned by Coming
Incor-porated, a publicly trading company that was
origi-nally established in 1851
Coming Cable was involved in a number of
impor-tant mergers in the early 2000s, including the
acqui-sition of Siecor and Siemens' global cable and
hard-ware businesses
Corning Glass Works Ahistoric glass company that
employed many significant pioneers in glass
tech-nologies and their application While working at
Corning's Sullivan Park Research facility, scientists
D Keck, R Maurer, and P Schultz demonstrated a
practical fiber optic waveguide that overcame the
limitations of earlier attempts by reducing the losses
associated with lightguiding over distances For their
work, they have received numerous awards,
includ-ing the 2000 National Medal of Technology
Corning Glass Works became Coming, Inc In 1943,
Dow Coming Corporation was formed and now
pro-duces a wide variety of silicon-based products
Corning Museum of Glass From decorative art
works to fiber optic components, glass has a long and
colorful history that is exhibited in the extensive
col-lections held in the Coming museum, located in
Com-ing, New York Scientific aspects of glass are docu-mented and demonstrated in the Glass Innovation Center http://www.cmog.orgl
corona A halo, glow, or other luminous surrounding from various causes including refraction, particle movement, ionization, radiation, reflection.St Vitus'
fire, as reported by sailors, is likely a kind of corona
effect Voltages around power lines and antennas can sometimes ionize the surrounding air, resulting in a whitish-blue corona effect
Corporation For Open Systems International COS Anonprofit vendor-supported organization cre-ated in 1986 It was established to further the accep-tance and use of data processing and data communi-cations equipment, and to encourage multivendor product compatibility in these areas COS is involved
in various standards efforts, particularly those in-volved with test methods and certification require-ments
Corporation for Research and Educational Net-working CREN Anonprofit organization fonned in
1989 when BITNET merged with the Com-puter+Science Network (CSNET) to promote and assist accessible, worldwide academic infonnation exchange In 1994, CREN announced a system to facilitate communications called Internet Resource Access (IRA), in essence an Internet-in-a-box sys-tem In 1996, it recommended to its members that they discontinue support ofBITNET in favor ofother systems, primarily the Internet Since the Internet has superseded BITNET as the dominant global commu-nications network, CREN has increased its focus on seminars, educational materials, and software utilities that enable academicians and technology profession-als to use and implement widespread, inexpensive network access for the purposes ofresearch, commu-nication (especially discussion lists), and distance education CREN is a founding member ofthe Inter-net Society (ISOC) See BITNET, InterInter-net Resource Access, LISTSERV http://www.cren.net!
corresponding entities In ATM networking, peer entities with a lower layer connection between them, coordinated through protocol control infonnation corrosion A wearing away, or alteration by chemi-cal action, often leaving a residue such as rust or film
as a byproduct ofthe corrosion Many electrical wires and components are coated or bonded in order to pre-vent corrosion Some elements resist corrosion, mak-ing them useful for applications in corrosive environ-ments See oxidation
CoS See class of service
COS 1 compatible for open systems 2 See Corpo-ration for Open Systems International
COSETI Columbus Optical SETI See SETI COSINE Cooperation for Open Systems Intercon-nection Networking in Europe Aprogram established
by the European Commission to utilize Open Systems Interconnection (OSI) to interconnect various Euro-pean research networks
COSPAS/SARSAT A cooperative effort begun by the United States, the USSR, France, and Canada in the later 1970s It supports satellite
Trang 6communications-information such as the location ofdistressed aircraft
or marine vessels to be communicated to rescue
sys-tems COSPAS/SARSAT operates in conjunction
with the emergency position-indicating radiobeacon
(EPIRB)to support the Global Maritime Distress and
Safety System (GMDSS)
COTS I.commercial off the shelf 2 See
Connec-tion-Oriented Transport Service
Cotton-Mouton effectWhen light passes through a
pure liquid in a direction perpendicular (normal) to
an applied magnetic field, the liquid becomes
dou-bly refracting See Kerr effect
coulombA unit of electrical quantity named after
Charles A de Coulomb Aunit for the amount
ofelec-trical charge in the meter-kilogram-second (MKS)
scale that passes through a circuit in one second at
one ampere (unvarying) current The international
coulomb is the quantity ofelectricity that will deposit
0.0011180 grams of silver when passed through a
neutral solution of silver nitrate in water A coulomb
can also be expressed as the quantity of electricity
on the positive plate of a condenser of a capacity of
one farad when the electromotive force is one volt
See ampere
Coulomb, Charles Augustin de(1736-1806) A
French physicist and engineer who experimented
with applied mechanics and electromagnetism In
1785, he demonstrated the laws of electromagnetic
force between elements using artificial magnets with
well-defined poles in which the associated
phenom-ena could be more clearly observed The Crater
Cou-lomb on the moon and the couCou-lomb unit of electric
charge are named after him
Coulomb's law Adescription of the magnitude ofan
electromagnetic charge Two electromagnetic point
charges will attract or repel one another with a force
directly proportional to the product of their charges,
and inversely proportional to the square of the
dis-tance between the two point charges This
phenom-enon is more easily observed than many in the field
of physics Named after Charles de Coulomb
Council for Access TechnologiesCAT Originally
founded in the early 1990s as the National ISDN
Council, with the wide deployment of ISDN
tech-nologies, the group broadened its focus and became
the Council for Access Technologies CAT is an
in-dustry trade association promoting the
implementa-tion, standardizaimplementa-tion, and simplification ofnew
tele-communications services offered over a variety of
access technologies CAT supports the exchange of
technical information and information about
compabitility and works with other organizations and
end users to introduce new networking services
http://www.CATcouncil.org/
counter-rotating ringIn ring network topologies,
data typically travels in one direction along each path
In a counter-rotating ring, there are two signal paths,
each one traveling in the direction opposite to the
other See Fiber Distributed Data Interchange,
Token-Ring
counterpoise1 A state of balance, counterbalance,
such that the opposing forces are equivalent, or bal-anced 3 A structure designed to balance the trans-mitting or conductive properties of a circuit counterpurposeWorking towards one goal and para-doxically achieving the opposite result to what was intended This term was coined by Doug West and has many applications in telecommunications tech-nology For example, when the Federal Communi-cations Commission frees more radio frequency spec-trum to ease a situation where demand exceeds sup-ply, it often spurs the development of new technolo-gies to take advantage of the newly available
spec-trum,with the result that demand exceeds supply by even more than was originally the case
couplerIn general, a connector to facilitate the join-ing of two elements; an elbow joint can couple two sections of pipe or a threaded (or bayonet) coupler can connect a camera to a microscope.Intechnology, the term often describes a mechanism for combining two or more cables or signals or for splitting a cable
or signal into two or more paths A coupler is a ge-neric component with applications for mechanical, electrical, and optical media
Optical couplers are used to branch optical power from a single fiber into multiple fibers or vice versa
A standard optical coupler handles single wave-lengths with designated ratios Broadband couplers may branch or combine optical power within a des-ignated wavelength range in a constant ratio For sys-tems design or troubleshooting, couplers may be used
to isolate circuits
Optical couplers can be fabricated by aligning opti-cal fiber cores closely enough for the signal to 'Jump" from one fiber to another By twisting and heating the fibers, the conductive fiber cores will fuse to facili-tate the transfer of light energy The portions of the fiber that are tapered in the fabrication process will influence the reflective properties of the light beams and trap thehigher order modesin a multimode fi-ber These are known ascladding modes,as they are
at the surface of the fiber where it is shielded by the cladding materials that keep light within the fiber waveguide As the signal moves through the fused region,lower order modesremain in the original fi-ber As the beams exit from the coupler and the ta-pered, fused region is left behind, cladding modes are converted back tocore modes.The degree of taper, the proximity of the fibers, the length ofthe coupling region, and the wavelengths coming down the fiber are important parameters that hinder or facilitate sig-nal resonance and coupling
A 1x2coupler, also known as a Y coupler or Y split-ter, is adirectional couplerthat enables two paths to
be joined into one or one path to be split into two.Y couplers/splitters are commonly used in fiber optic networks A2x2coupler has eight possible indi-vidual paths through which the signal may travel for
a bidirectional signal and four possible individual paths for a unidirectional signal Combining the cou-plers increases the number ofpaths (and the complex-ity of the combinations and control mechanisms)
Trang 7Fiber Optics Illustrated DictionanJ
Couplers can be combined in tree-like branching
structures to form multiple outputs from a single
source Note that loss is typically associated with
splitting a signal Asufficientlly powerful source
sig-nal or sigsig-nal amplification may be needed in a
cir-cuit with many branches
A coupler may be connected to a fiber optic network
by fusion splicing or through low-loss connectors
at-tached to the coupler Pigtails are protruding
fila-ments intended for making connections Commercial
housings, some of which are rack mountable, are
available for supporting multiple couplers
Depend-ing upon the configuration, the coupler may require
a termination adapter See SC-connector, ST-connector
coupler, star A type of coupling configuration in
which a signal is split into multiple paths which may
continue on through a circuit or be reflected back to
multiple positions adjacent to and including the
sig-nal source In optical star couplers, an input light
beam is transmitted to all output ports
coupling loss Loss in a conductive medium that is
directly related to the physical properties of the
cou-pling mechanism Coucou-pling losses can be due to poor
materials, poor shielding, loose connections,
rota-tional incongruities between the coupled ends,
par-ticles, heat expansion, humidity, etc
Coupling loss is more prevalent and more significant
in fiber optic cables than in most wired connections
due to the precision needed to guide light along a link
in a path
The units for expressing coupling loss depend upon
the type of conducting medium and conductive
phe-nomenon In other words, it will be expressed
differ-ently depending upon whether it is a wire or optical
cable and whether the conducted signal is
electric-ity, light, X-rays, or sound It will also depend upon
the relative magnitude of a typical loss and the type
of signaling that is used For example, coupling loss
ina light transmission may be expressed in terms of
loss ofpower (e.g., light intensity), whereas coupling
lossinan acoustic medium may be expressed in terms
ofloss ofintelligibility (e.g., the number ofwords
cor-rectly understood) See attenuation, coupler, fusion
splice
cover page The first page of a printout or facsimile
that identifies information about the nature and date
of the printout, and often the sender and intended
re-cipient On networks with shared printers, it helps
identify the owner of the hardcopy See banner
coverage area In news and entertainment
broadcast-ing and cellular communications, the geographic
range of users/subscribers Outside of the coverage
area, signals will be weak or absent This is not a
prob-lem for broadcast subscribers, who usually know they
are either inside or outside the range ofa certain
chan-nel, but for mobile communications users driving out
of range in the middle of a conversation, it can be a
problem For this reason, some mobile
communica-tions will provide a signal that indicates that the
lim-its of the range are nearby, and some handsets will
have a light or message that indicates the user is
out-side the service range
Fiber Optic Coupler - Duplex
Duplexfiber optic cables can be interconnected with
Bel/Core has published compatibility specifications that arefollowed by a number ofmanufacturers Cou-pling ratios may vary, depending upon the applicatioll.
CP/M Control Program/Monitor, Control Program for Microcomputers.Anoperating system that came into widespread use in the late 1970s and early 1980s, written by programmer and professor Gary Kildall
It had a text-based, line-oriented interface and ran on the Intel 8080 and Z80 microprocessor families Kildall formed Inter-Galactic Digital Research, later Digital Research, to market his computer software products The forerunner of MS-DOS was derived from a CP/M manual by Tim Paterson and is basi-cally the same in syntax and functionality Digital Re-search continued to develop CP/M into CP/M86, and later DR-DOS Kildall also created a multitasking version of the operating system and personal com-puter networking software long before they became common on personal computers See Digital Re-search
CPA 1 Charter Public Accountant 2 See Chip Pro-tection Act
CPCS See Common Part Convergence Sublayer CPE See Customer Premises Equipment, Customer Provided Equipment
CPI See common part indicator
CPL commercial private line
CPN See Calling Party Number
cps See characters per second
CPS See Cellular Priority Service
CPU See central processing unit
CQ In early radio transmissions, CQ was often used
as a call to operators (all stations) as a way of getting general attention There are some historians who believe CQ may also have been used as a distress call, and some have interpreted it as meaning "Come Quick" although this may have been attributed after the abbreviation had been around for a while Baarslaq has written that the Marconi Company re-questedCQDto be established as a distress call
Trang 8(pre-eral CQ call in early 1904.
CQDAradio distress call which predated SOS See CQ
CR1 See carriage return 2 call reference 3.symb.
right-hand circular or direct polarization (ITU)
4 connection request.AnOpen Systems Interconnect
(OSI) transport protocol data unit 5 customer record
crackerAspecific subset or connotation of"hacker"
for someone who gains unauthorized access to
sys-tems or applications Since breaking into syssys-tems can
sometimes be done through sheer persistence and
brute force techniques, not all cracking is hacking in
the sense ofapplying brilliant and elegant solutions
The term was derived fromsafe crackersince
crack-ing a software password is somewhat analogous to
cracking the combination on a safe One of the most
widespread activities of crackers is the deciphering
ofpasswords for computer games so they can be
dis-tributed and played without paying fees to hard
work-ing game producers See hacker
CRAFTSee Cooperative Research Action For
Tech-nology
crankbackIn ATM networks, a mechanism that
al-lows the release of a connection setup that has
en-countered an error condition (as in a failed Call
Ad-mission Control) to permit rerouting of the
connec-tion
crammingAnundesirable practice in which
telecom-munications services customers are billed for a
num-ber ofenhanced features (e.g., Call Waiting) that were
not requested or ordered
crashSystem failure, lockup On a computer, a crash
usually implies a complete lockup of the operating
system (this shouldn't happen and very rarely
hap-pens on good operating systems) and usually requires
a reboot Ifthe operating system is robust and remains
functional after an applications crash, the offending
application can often be "killed" to remove it from
the system and to prevent it from affecting other
ap-plications.Itis generally done this way on Unix
sys-tems Killing the application and processes
associ-ated with the application will also free any memory
that may be inaccessible due to the crash
There are many ways in which a system can crash
Less common causes are hardware failures or
elec-trical anomalies The most prevalent causes are
soft-ware problems, especially applications memory
man-agement and operating system memory manman-agement
Endless loops and bad pointers can also cause crashes
Cray, Seymour(1925-1996)For a whole generation
of computer users, Seymour Cray's name was
asso-ciated with some of the most powerful
supercom-puters in the world Cray grew up with a strong
in-terest in electronics and computing at a time when
computers were mainly used by the military and not
much was known about them Cray founded Cray
Re-search Inc in 1972 and Cray Computer Corporation
in 1989, companies known for high-end computers
for over 20 years The Cray 1 supercomputer was
announced in 1975 and the Cray 2 in 1983
Supercomputers attract less excitement now than they
did a decade ago because the general processing
ers have increased so dramatically that the distinc-tion between high-end and low-end systems is less dramatic Many supercomputing operations are now run on desktop computers internetworked with the Linux operating system This operation is very cost-effective for research labs, educational institutions, and government agencies
CRC 1 See Communications Research Centre
2 See cyclic redundancy check
CRC PressThe publisher of this reference, CRC is one of the world's oldest and most well-respected technical publishers, based in Boca Raton, FL CRC first published theHandbook ofChemistry and Phys-icsin 1913, an enduring reference that has been re-printed more than 80 times as a definitive source for generations ofscience students and professionals The company now has several imprints and ships books all over the world http://www.crcpress.com/
credentialsIn computer security, documents or ex-pressions of trust and confidence,particul~ly those that indicate the capability to perform a function or task The Pretty Good Privacy data encryption sys-tem has an interesting aspect related to credentials in that parties can vouch for the good name and verac-ity of public key holders See Pretty Good Privacy
credit card phoneApay telephone equipped with a card slot instead ofor in addition to a coin slot to read magnetized credit cards and calling cards These are becoming increasingly common and are handier than phones where long credit card numbers and pass-words have to be manually keyed
Creed Telegraph SystemA system designed by Ca-nadian inventor Frederick Creed with a typewriter-style tape-punching machine It improved upon the speed and utility of existing manual punchers and began commercial distribution in 1908 His auto-mated perforators could operate up to 150 words per minute To this he added a translating and printing system, which eventually became a teleprinting trans-mitter/receiver system sold in England by 1927
Creed, Frederick George(1871-1957)ACanadian inventor and telegraph operator who developed the Creed Telegraph System, an automated teleprinting transmitting/receiving system, in 1889 He then trav-eled to England to manufacture the Creed Printer By
1898he had demonstrated he could send telegraph messages at sixty words per minute, and his inven-tions were put into commercial use by 1913 Creed was a member of the Board of Directors for the In-ternational Telegraph & Telephone Company (ITT) See Creed Telegraph System, telegraph history
creel1.Awoven basket for storing objects or crit-ters (installation tools, caught fish, birds, picked apples) 2 A quantity, as might traditionally be held
in a basket The tenn is applied to fishing limits, for example 3 A single support frame or multiple as-sembly for holding spools of cable on winding pegs Winders may be attached to each peg or spools may
be wound before hanging on the creel pegs, depending upon the application The term comes from the fab-ric industry (e.g., woollen mills), where multiple
Trang 9Fiber Optics Illustrated Dictionary
spools of thread can be wound on a creel assembly
anddrawnoff to other creels or mechanisms
(warp-ing creels or looms) Creels can support and organize
multiple cables for production or storage They are
also used for supporting and spooling raw fiber in
preparation for cladding
Creighton, Edward (1820-1874) Creighton was
ex-perienced in building communications lines and roads
and thus became the organizer of the western
expan-sion of the telegraph system for Western Union,
un-der Sibley and Cornell Creighton surveyed the first
transcontinental route across the wilderness in 1860,
which followed the trails of the recently established
Pony Express Creighton worked in conjunction with
the Overland Telegraph Company to carry out
con-struction on the section west of Omaha
In those days, building a line involved more than
muscle and materials; it required bushwhacking
through roadless, supplyless, lonely wilderness areas
inhabited by wolves, coyotes, snakes, and bears The
vast tracts were without urban comforts of any kind
It also involved negotiating with native inhabitants
and working out problems associated with roaming
herds ofbuffalo who thought the telegraph poles were
installed for their convenience as backscratchers The
line construction was originally estimated to take two
years at a cost of over a million dollars Under
Creighton's supervision, the job was done in four
months at a fraction ofthe original cost estimate
For-tunately, Creighton owned stock in Western Union
and was able to benefit from this astonishing
engi-neering feat He used his gains to found Creighton
University and to contribute to many civic projects
CREN See Corporation for Research and
Educa-tional Networking
CRF 1 See cell relay function 2 See
connection-related function
crimp To squeeze so as to confine; to push in upon
crimp tool, crimping tool Acommon handheld
wir-ing installation tool that resembles a fat, snub-nosed
set of pliers It is designed to facilitate the cutting,
stripping, and crimping of wires or fiber optic cable
by providing rounded pressure points and leverage
for exerting pressure Crimp tools may have more
than one gauge or setting for related tasks
In fiber optic cable assembly, a crimp tool makes it
easier to tighten and secure a crimping sleeve that
slides over the jacketed fiber and its attached
connec-tor It may also be used to tighten a strain relief boot
that fits over the crimpling sleeve Care must be taken
to exert the correct amount of pressure when
crimp-ing, to avoid breaking a wire or fiber filament See
lapping film
CRIS See customer record infonnation system
critical angle The angle at which a beam is reflected
within a transmissions medium such as optical fiber
This angle can be very important to the strength of
the signal over distance and the total distance the
sig-nal can travel It may be modified by the angle ofthe
beam, the thickness of the fiber, and various
impuri-ties (doped elements) that may have been introduced
See acceptance angle
critical charge The amount of charge needed to ini-tiate a process or to change the state of or value of data being stored or processed
critical fusion frequency CFF In a display device, the refresh rate frequency above which the individual scans are fused by human perception into a single frame or image It is not a set number, as, for example,
on a cathode-ray tube (CRT) display; it is related to the rate of persistence of the visible light from the excitation of the phosphors As a rule of thumb, though, most systems show a nonflickering image at about 60 frames per second, or at about 85 Hz Critical Technologies Institute CTI Organization established within RAND by an Act ofU.S Congress
in 1992 and primarily sponsored by the White House Office of Science and Technology Policy CTI works with the Federal Coordinating Council for Science, Engineering, and Technology to assure that technolo-gies critical to national interests are identified and supported
CRITO See Center for Research on Infonnation Technology and Organizations
CRM See cell rate margin
CRMA See Cyclic Reservation Multiple Access Pro-tocol
Crookes Dark SpaceIna cathode-ray tube (CRT),
as the gas pressure in the tube is gradually diminished, the glow surrounding the cathode detaches, leaving
an area that is dark around the electrode, an area that may become quite large at low pressure levels In a tube that has some air in it, this region can be more easily distinguished as being between the cathode glow on the inside and the negative discharge glow
on the outside Outside the negative glow is another region called the Faraday Dark Space See Faraday Dark Space
Crookes tube Asimple experimental tube developed
by William Crookes in the 1870s for studying elec-trical discharges Essentially a variation on the Geissler tube, which was filled with various types of gases to observe their effects, the original Crookes tube was attached to a pump to evacuate the gases, and the two ends supporting the cathode and anode electrodes were sealed off to maximize the stability
or controllability ofthe environment within the tube (In fact, a complete vacuum was not achieved and,
in some cases, the effect ofrarified gases in the tubes was being studied.) The electrodes were connected
to a source of electrical charge with the voltage con-trolled to fonn a crude ampmeter for detecting cur-rent The Crookes tube also facilitated the discovery
of X-rays (Rontgen rays).Insome cases, a mineral substance was mounted within the glass tube to cre-ate fluorescing effects when voltage was applied across the tube electrodes Like the Geissler tube, this illuminated effect made Crookes effects popular in English parlors at the time
Later refinements of the Crookes tube made it pos-sible to control cathode rays, an important step in the development ofcathode-ray tubes, which are used in television, imaging, and display technologies Crookes tubes are used in educational settings for
Trang 10flow and the influence ofmagnetic forces on this flow.
See cathode-ray tube, Geissler tube
Crookes Tube
The Crookes tube was an important experimental
electron tube that was used by William Crookes
be-ginning in 1870s, and later by other scientists, to
re-search voltage levels and electromagnetic radiation.
It also contributed to the development ofpioneer
dis-play technologies such as cathode-ray tubes.
Crookes, William (1832-1919)AnEnglish
physi-cist, chemist, and editor who developed scientific
in-struments for studying various phenomena and used
them to make some important basic discoveries
Crookes founded theChemical News,a weekly
pub-lication he edited for almost 50 years, though he is
better known for investigating the effects obtained by
passing electrical charges through various gases One
ofhis more notable achievements is the discovery of
thallium in the 1860s Further studies of thallium led
to the invention ofthe Crookes tube in the late 1870s
He designed a vacuum-sealed glass tube for
detect-ing charge that could be used to investigate the
rela-tionship between voltage and pressure He later
de-veloped an instrument for detecting radioactive
par-ticles Crookes tubes were subsequently used by
Rontgen in his discoveries of X-rays See Crookes
Dark Space, Crookes tube
cropping The process oftruncating infonnation,
usu-ally an image Cropping refers to the removal of
un-needed elements or data For example, excess blue
sky may becroppedfrom a photo during the
devel-opment process or after the photo is printed
Crop-ping does not imply any change in size or proportions
to the remaining portion of the image In computer
imagery, the cropping may involve removing the data
only from the display area, the data regarding the
'hid-den' or cropped information may still be in the
computer's memory so it can be quickly restored, if
needed Cropping ortrimmingis often done by
print-ers when cutting down print jobs thatbleedoutside
print boundaries See clipping, scaling
ming and translation tool that enables assembly lan-guage symbolic coding to be written on one system
to run on a different type of system This is conve-nient because development machines often require more resources (more speed, memory, etc.) than the system on which the software will eventually run There may not even be a machine available on which
to run the software until the software is partly or mostly written, due to production schedules or cost
A cross assembler enables software development to get underway and continue somewhat independently
of the hardware schedule
cross connect Apoint in a circuit where a new or tem-porary connection is created by wiring between ex-isting circuits or between facilities Used variously for diagnosing problems, rerouting, or adding circuits Cross-Industry Working Team XIWT An organi-zation established to promote the understanding, de-velopment, and application ofcross-industry National Information Infrastructure (NIl) visions into practi-cal technologies and applications, to facilitate com-munication between stakeholders in the public and private sectors The XIWT Web site provides links
to information, many reports, and white papers http://www.xiwt.org/
crossbar switch In older mechanical telephone switching systems, a crossbar switch was similar to
a relay, except that it was controlled by two external circuits and was used in more complex switching ar-rangements, such as those needed for long-distance connections It was devised in the late 1930s, and AT&T developed a version based upon pioneer work
by Swedish engineer GotthilfAnsgarius Betulander
In 1938, the first crossbar central office went into service in Brooklyn, the same year the infamous "War ofthe Worlds" broadcast frightened credible residents
of the area (who tied up phone lines in their panic) The crossbar switch eventually succeeded the widely used but troublesome panel switch in the 1950s and step-by-step switches in the mid-1970s See Callender switch, Lorimer switch, panel switch, step-by-step switch
crossover cable Acable in which a pair of wires are reversed at one end of the connection This reversal
is commonly done to convert a serial communications cable to a null modem cable In this case, the trans-mit (Tx) and receive (Rx) wires are crossed, or switched over.InRS-232 specification cables these are lines two and three
crosstalk A term for undesirable electrical interfer-ence, usually from nearby lines, in which the signal from one cable or component is close enough and strong enough to impinge on the signals in another cable or component In telephone cables or switches, the crosstalk may be so excessive that a telephone conversation from another line can actually be heard Crosstalk usually occurs in installations with inad-equate spacing or shielding
crosstalk, optical Fiber optic cables do not exhibit the same electrical leakage and crosstalk character-istic of tightly bundled or poorly shielded electrical