Early ra-dio sets were called "crystal detectors" as they used crystals galena and carborundum were popular to detect rectify and channel a radio wave.. In 1904, Christian Hiilsmeyer 188
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late 1980s and the 1990s and, more recently, has
in-troduced Super DLTtape technologies that provide
fast transfer-rate, high-capacity storage on tape
car-tridges See Super DLTtape
Quantum Flow Control QFC.InATM networks, a
congestion avoidance scheme proposed for use on
available bit rate (ABR) connections For example,
in a network in which VCI tunneling is implemented,
the ATM device will send only after receiving explicit
credit from a receiving ATM device at the other end
of the connection If tunneling is not used, buffer
al-location and a credit manager must be included If
the buffer allocation is exceeded, noncomplying cells
will be discarded
quantum mechanics The study of atomic structure
and behaviors using various measuring instruments
and techniques See Heisenberg uncertainty principle,
quantum
quantum noise When using a detector to investigate
quantum characteristics in electromagnetic
phenom-ena, there may be noise from random variations or
fluctuations in the average rate ofincidence
ofquan-tum interactions with the detector These may be
ex-pressed in terms of photons
quantum well QW Aquantum phenomenon
associ-ated with a structure fabricassoci-ated from ultrathin
alter-nating layers of wide bandgap (barrier) and narrow
bandgap (well) materials When an electron is caught
in a well formed between the barriers, the
probabil-ity of escaping the well is limited and the electron's
energy level is affected The quantization effects
re-sulting from these events are related to the height and
width of the fabricated barrier and can be derived
through quantum mechanical calculations Quantum
well exhibiting structures can be constructed using
crystal growth techniques (for use in quantum
cas-cade lasers, for example) Quantum well components
have unique properties that can be exploited for a
variety ofoptical communications technologies
Quantum well physics can be used to create
modula-tors through the application ofan electrical field
per-pendicular to the surface of the quantum well or
al-ternately to its sides Thus, the optical absorption of
the QW is changed sufficiently to make it useful for
signaling This phenomenon can be exploited for
semiconductor design to make small optical
modu-lators with two-dimensional optical arrays
A quantum well infrared photodetector (QWIP) is a
multiple quantum well device based upon layered
high-bandgap semiconductor fabrication Bandgap
discontinuity associated with the layers of differing
materials creates quantized subbands in the potential
wells The phenomena associated with the layers is a
photoexcitation ofelectrons between ground and first
excited-state subbands The carriers resulting from
the photoexcitation are then able to escape from the
potential quantum wells to generate a photocurrent
In the U.S Naval Research Lab, quantum well
phys-ics has been used to develop a number of types of
semiconductor lasers emitting mid-infrared light
Using "wavefunction engineering," engineers have
designed complex, layered quantum well structures
This has a number of possible applications, includ-ing laser radar (ladar)
Researchers at Imperial College demonstrated a new quantum well solar cell (QWSC) that may be more efficient than previous solar energy sources
In 1997, scientists described an uncooled strained quantum well laser that could be used in SONET/ SDH networks, especially short- and medium-haul transmissions
See electroabsorption, quantum cascade laser, self-electro-optic effect device
Quarter Common Intermediate Format QCIF, Quarter CIF Astandard for the transmission ofvideo frames in thelTU-T H.261 standard QCIF consists
of 144 lines of luminance and 176 pixels per line (144 x 176 CIF format is optionally supported by H.261) This relatively low resolution creates an im-age that has a soft-focus, indefinite appearance, but has the advantage of using fewer system resources and less bandwidth In fact, the standard was devel-oped with the needs of circuit-switched networks in mind For small windows, simple images, and small display devices, it has practical applications, and it
is widely favored for videoconferencing, especially
on ISDN networks H.261 is usually implemented in conjunction with other related standards See Com-mon Intermediate Format
Quarter Inch Cartridge Drive Standards QIC.An international association, established in 1987, to pro-mote the acceptance and use ofquarter-inch readable/ writable data cartridge drives and media These types
of storage media are commonly used for computer backup, secondary storage, and temporary storage for files that need to be transported
More than 100 QIC standards have been developed since 1988 40, 80, 3101, and
QIC-3020 have been particularly prevalent in the tape car-tridge field, although they are now being superseded
by higher capacity formats Acomplete list and fuller description ofeach standard are available on the QIC Web site http://www2.qic.org/
quarter wave The distance, or elapsed time, in a con-ducting line or through a concon-ducting space, which is 90° to a wave disturbance This information in used
in the design ofantennas and in the quadrature trans-mission of signals, particularly in modulation schemes See quadrature
quartz A silicon dioxide mineral found or synthe-sized in crystal fonn and in crystalline masses, which
is widely used in scientific research and telecommu-nications due to its oscillating qualities Quartz is transparent, harder than glass, and varies in its oscil-lating frequencies depending upon its size and shape Quartz crystal watches are extremely accurate, and quartz arc lamps are used for sterilization, due to the way ultraviolet light passes through the crystal See piezoelectricity
QuartzA2D graphics engine from Apple Computer, based upon the standardized Portable Document For-mat (PDF) Quartz is incorporated into Mac OS X quartz(symb - Si02)A mineral silicate of the sili-con dioxide quartz group with a unique helical
Trang 2applications in electronics.
quartz crystal componentA piece of quartz cut to
a precise size for a specific purpose Quartz has
re-markable constancy in its vibratory qualities,
mak-ing it suitable for extremely precise time devices
These vibratory qualities can be controlled by
ma-nipulating the shape and size of the crystal Early
ra-dio sets were called "crystal detectors" as they used
crystals (galena and carborundum were popular) to
detect (rectify) and channel a radio wave Quartz is
commonly used in oscillators and filters Quartz
crys-tals are used to provide timing in watches and to
stabi-lize broadcast waves See quartz, quartz crystal filter
quartz crystal filterThe properties of quartz
crys-tals make them useful for a variety of applications
that require highly selective electrical circuitry, and
hence they are used in the creation of various types
of filters Synthetic quartz crystals, developed in the
1950s, furthered the manufacture ofquartz filters for
use as electronic components There were, in fact,
few other materials that offered the advantages of
natural or synthetic quartz until the development of
lithium-tantalate crystals in the Bell Laboratories See
lithium-tantalate, quartz, quartz crystal
quartz tuning forkQTF A specialized instrument
exploiting the piezoelectrical properties ofquartz In
1995, it was suggested by Karrai and Grober that
QTFs could be used for measuring shear forces on
scanning near-field optical microscope (SNOM)
fi-ber tips Subsequent research has led to the
develop-ment of QTF mechanisms for non-optical distance
stabilization in atomic force microscopes (AFMs) for
the realization of apertureless SNOM See scanning
near-field optical microscope
quaternary phase-shift keyingQPSK A
modula-tion technique which is used to encode digital
infor-mation to be transmitted over wire or fiber networks
Itis a subset of phase shift keying (PSK), and is
es-sentially a four-level version of phase modulation
(PM) QPSK divides the bit stream into two streams,
and sends them alternately to in-phase and
out-of-phase modulators, where they are subsequently
de-modulated at the receiving end
QUBEAnInteractive TV information utility Warner
instituted the QUBE interactive educational TV
net-work in the late 1970s The first interactive
televi-sion concert, broadcast live over the QUBE system
in 1978, featured Todd Rundgren, pioneer
multime-dia recording artist
quenchTo bring to a sudden halt, to cool rapidly, to
quickly extinguish a flame, spark, or gas emission
quench oscillator Insome super-regenerator circuits,
a type ofultrasonic oscillator which serves to quench,
or rapidly reduce, the regeneration when it has almost
increased to the point of oscillation
quenched spark gapEarly wireless transmitters used
spark gaps in their spark transmitters, with several
types of gaps: open gaps, rotary gaps, and quenched
gaps, each with different strengths and weaknesses
Quenched gaps employed a racklike series of metal
plates separated by thin layers ofmica, resulting in a
not tend to overheat as do open gaps Due to improve-ments in technology and the need for regular clean-ing to keep quenched gap transmitters workclean-ing opti-mally, they were eventually superseded by continu-ous wave (CW) transmitters
query 1 Request for data, in which the content of the data is the desired result Common in database applications 2 Request for data which provides in-formation about the state (operating parameters, mode, security, etc.) or functioning (availability, readiness, status, responsiveness, etc.) of a system Usually at a low operating level and generally trans-parent to the user
query by exampleQBE.Anidea introduced in the 1970s whereby a user interacts with a front end to a database by supplying examples ofthe type of infor-mation that the user wants to retrieve Sometimes this
is more practical than querying by keywords or al-gorithms A number of popular database programs provide this capability
query languageAprogramming language intended
to facilitate search and retrieval of information, usu-ally from a database Query languages are frequently
in the form of interpreted scripting languages or graphical report generators, with commands that are similar to common English words, to make them easier to program by those without programming backgrounds
Query on ReleaseQoR A telephone number port-ability mechanism suggested by Pacific Bell to trig-ger a database query, depending upon circumstances related to a subscriber's current carrier.InQoR, a tele-phone call setup signal is routed to the end office switch to which the dialed phone number was origi-nally assigned (e.g., the NPA-NXX ofthe dialed num-ber) Ifthe dialed number has been transferred to an-other carrier's switch, the database is queried for rout-ing information and the call completed to the new switch The system is also called Look Ahead
In 1997, the Federal Communications Commission affirmed its conclusion that this (interim) solution was not acceptable over the long term because it violated
a statutory requirement for consumers to retain num-bers without impairment ofthe quality, reliability, or convenience when switching carriers The Commis-sion felt that degradation in service in terms of post-dial delays could compromise QoR forwarding and supported Location Routing Number (LRN) as statu-torily acceptable See Release to Pivot
queueA stream of items or tasks waiting to be pro-cessed or executed, such as calls to an operating sys-tem, a network, or a phone system Queues are used
to maximize the use ofexisting resources, especially
on shared systems It's expensive to put a printer on every computer in a network and, since printing doesn't happen as often as data input/output, it's not efficient either By allocating one printer to every few workstations, user print requests can be handled ef-ficiently by the network, with simultaneous requests administered through a set of parameters This also can improve resource choice By sharing printers, it
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may be possible to offer a variety oftypes ofprinters
and paper sizes, which is more practical and
economi-cal than trying to purchase several printers for each
computer See queuing
queue administrationQueues are widely used to
manage resource-sharing on a network Whether the
resource is a printer or modem, applications program,
data file, or gateway to the Internet or Web, computer
systems create, manage, authorize, and prioritize
ac-cess to these resources and services through queues
which are usually transparent to the user
On phone networks, queue administration may
in-volve putting a caller on hold, checking to see if and
when agents are ready to take the call, playing
peri-odic messages to the caller, and assigning the call to
the appropriate agent
On computer networks, queue administration may
involve logging in users as they sign on to the
sys-tem, checking for the existence of devices when a
resource request occurs (e.g., a printing job),
deter-mining if others are in the queue, and where to slot
the new request (the size of the print job, or relative
priority of the user requesting the job may be taken
into consideration), and may even change the
queu-ing arrangement dynamically ifanother printer comes
online or aprint request is canceled before thejob is run
Queued Telecommunications Access Method
QTAM.AnIBM communications control protocol
which handles some applications processing tasks
QTAM is used in a number of telecommunications
applications, including message switching, data
pro-cessing, etc
queuing delayQD In its most general sense, a
de-lay caused by queues or lineups within a system
through which objects, information, or data are
chan-neled As a simple example, shopping in a downtown
store with a queue at the cash register can result in a
delay that causes a shopper to receive a parking ticket
When placing a phone call, a delay may be imposed
on the caller by congested trunk lines or by the
vari-ous switchers, routings, and routing priorities
inher-ent in or configured into a system Queuing delays
can have many negative effects including customer
frustration, loss of revenue, extra costs, and even
death (in the case of emergency calls), so queuing
theories and solutions are considered to be an
impor-tant aspect of telecommunications
The queuing delay in a transmission system can be
assessed in terms of particular legs within a route or
in terms of a transmission as a whole, from sender to
recipient This is often a dynamic process without a
single catch-all solution Queuing delay is often
evaluated in conjunction with other types of delays,
including processing, propagation, and transmission
delays Queuing refers to those aspects where data
or objects "bump up" against one another, in the sense
that (usually) similar objects congregate "behind" one
another in order to pass through a gateway or other
channel that cannot accommodate the queued
enti-ties simultaneously
Incell-based transmissions, a queuing delay is a
de-lay imposed on a cell due to the current inability of
the cell to be passed on to the next element or func-tion (because of congesfunc-tion or errors) Depending upon the system and priorities, significant delays may have several results; the buffered cell data may be re-turned or destroyed See queuing theory
queuing theoryQueuing, in its broadest sense, in-volves an understanding of mathematics, statistics, modeling, data flow, and human behavior as they re-late to the ways in which machines may be config-ured, tuned, and operated so as to carry out worth-while tasks and processes in an efficient and orderly manner Researchers in queuing theory regularly come from fields such as probability mathematics, complex systems theory, and simulation research
In the context ofnetworking, queuing theory focuses
on understanding, describing, and predicting patterns
in transmission organization, priorities, delay, loss, and standards for quality of service (QoS)
One of the most important pioneers of queuing con-cepts was Danish telephone engineer A.K Erlang, who studied and described telephone traffic in its mathematical context and practical applications in the early 1900s Another significant contributor to the body of knowledge in queuing theory is Leonard Kleinrock, who was involved in the early develop-ment of the ARPANET and who authored Informa-tion Flow in Large CommunicaInforma-tion Nets,in 1961 He subsequently wroteCommunication Nets, in 1964, which provides design and queuing theory for build-ing packet networks, in spite ofa common sentiment
at the time that packet switching wouldn't work Queuing theory is an important aspect ofperformance evaluation and configuration in communications net-works Without a theoretical model for installing, configuring, and tuning a network, much time can be wasted in trying out the many different ways in which network traffic can be routed, especially in a heavily used system in which congestion and "bursty" traf-fic occur Queuing applies to a broad range of envi-ronments, from individual circuit transmissions to global distributed networks
A single queue system is one of the most basic mod-els discussed in queuing theory When all traffic is routed through a single channel on a come, first-served basis (e.g., a single cash register in a comer grocery store), the impact of extra traffic and over-flow may be different from traffic management in multiple queue systems (a supermarket with multiple cash registers or multiple tumstyles at a sports sta-dium) The same concepts can be applied to telecom-munications systems.Asingle phone routed through
a dedicated line will be managed differently from a single line through a public phone system (wireline
or wireless) where congestion might occur The prob-lems of queuing become more intricate when mul-tiple users of mulmul-tiple phones (or modems) are shar-ing network resources over a public network, espe-cially in distributed networks where individual nodes mayor may not be available at any particular point
in time See Erlang, Agner; queuing delay
QUICCSee Quad Integrated Communications Con-troller
Trang 4quickly and easily making electrical connections
without the necessity of learning to use specialized
tools and wiring codes Quick connection blocks are
typically made of plastic or other nonconductive
materials with metal terminal connecting points and
may be preterminated for ease of installation They
are sold for avariety ofuses, including electrical
wir-ing, quick installation of multiple lights, computer
network connections, and internal telephone line
in-stallation, especially for multiphone systems
Quick connection blocks are especially appealing to
small businesses installing their own phone systems
These blocks enable wires to be inserted with easily
available screwdrivers, pliers, and wire cutters rather
than punchdown tools One common configuration
for telephone quick connection blocks is a premade
66 block,so-called because it supports up to 66
cross-connections
Panasonic has a commercial Quick Connect Block,
a premade 66 block, that connects to the standard
building wiring and supports up to eight analog or
digital phone stations for each block (depending upon
the phone model)
Homaco, Inc provides premade 66 blocks for
tele-phone connections in 25-, 50-, and 100-pair sizes
Comm-Omni International supplies cable termination
and surge protection for cables for multiple-family
residences and office buildings (e.g., private branch
exchange terminations) with a quick connection
block accessory with 50 6-pin interconnected rows
Quick File AccessQFA Asystem for enabling faster
access to data on tape-based storage systems such as
computer cartridge drives Prior to QFA and similar
systems, tape drives had to read through blocks of
data sequentially to find the desired data, resulting
in slow read times, especially ifthe desired data were
near the end of the tape With tapes and data stored
on tapes getting longer, this became impractical
Thus, a system of commands known as Quick File
Access enables a block number to be read so that the
tape can be fast-forwarded to the appropriate place
in the tape to locate the data Since the block
infor-mation pointers cannot be easily manipulated on tape,
they are usually held in a database Unfortunately, if
the database is compromised (or logging disabled),
then data location can be a problem (especially if it
is a backup tape to restore a crashed system upon
which the database was stored) Nevertheless, QFA
is much more convenient than traditional
serial-ac-cess tapes
quick-break fuseA type of fuse which breaks a
cir-cuit very quickly if a surge or other anomalous
elec-trical condition occurs Quick-break fuses are
espe-cially useful with electronics components, which are
sensitive to electrical fluctuations and prone to damage
QuickDrawA widely used proprietary computer
drawing and display specification from Apple
Com-puter Inc QuickDraw can display screen images and
processing PostScript files so they can be printed on
nonPostScript-equipped printers
quicksilvercolloq.mercury
display, audio, and animation environment from Apple Computer Inc that runs on Macintosh, Power-Mac, Windows 95, Windows NT 4.0, Windows ME, and Windows 2000 QuickTime is actually a suite of software applications for supporting picture display, multimedia authoring, and server support for stream-ing audio/video
QuickTime allows some interesting applications to
be developed and distributed, including frame-based animation, whiteboarding, video clips, teleconferenc-ing applications, virtual reality environments, games, and more The QuickTime fonnat is widely supported
on the Internet, with many Web-based multimedia applications distributed in QuickTime Many digital cameras also support the QuickTime format
Most recently, QuickTime has been enhanced to sup-port streaming media in Internet browsers (HTTP, RTP, RTSP) to support more than 30 different audio and video file formats (AIFF, BMP, GIF, JPEG, MPEG-l, MP3, M3U, PICT, PNG, SGI, Targa, TIFF,
VR, Wave, and more), and added modules for sav-ing digital video (DV) camcorder formats for the de-velopment of digital video
Most QuickTime software is freely distributed, in-cluding the QuickTime Player and PictureViewer
The QuickTime Streaming Server and Darwin Streaming Server are also freely distributed, with no streaming data license fees See QuickTime chart
quiet tuningIn radio receivers, a tuning character-istic in which the signal is kept quiet, that is, not broadcast to the listener, except when the tuner is
~~~:i~~~:?~~l~:J~~~~~~.a I~~~~~~~J:.e~cr; II isn't a good signal, the receiver mutes the sound to
save the listener from the distraction ofweak or noisy stations
Quorum InternationalThe marketing and distribu-tion arm ofApplied Electronics, a Hong Kong-based Original Equipment Manufacturer (OEM) Applied Electronics supplies many major computer and com-munications companies, including National Semi Conductor, IBM, Texas Instruments, and others
Products include security systems and pagers.In con-junction with MCI, the MCI-Q Program was devel-oped to enable Quorum to purchase communications products and services at special rates Through the Quorum Associate Distributor (QuAD), distributors receive discounted Mel Q-Connection rates and ac-cess to additional services (pagers, calling cards, etc.)
Quorum Teleconferencing BridgeA commercial, integrated voice and data device from AT&T to fa-cilitate conference call set up and administration The Quorum Teleconferencing Bridge connects and con-trols multipoint conference calls It enables a local operator to set up, control, and monitor up to four si-multaneous conference calls from participants in up
to seven locations for each call (or a single meeting with up to 28 locations)
QWERTY A ubiquitous computer and typewriter keyboard configuration designation, named after the six lettered keys on the top left side Although each
Trang 5Fiber Optics Illustrated Dictionary
computer keyboard has different symbol and
func-tion keys, most follow common QWERTY
configu-rations QWERTY was originally designed to slow
down typing to prevent jamming on old manual
type-writers (they jam easily)
Other keyboard layouts have since been proposed
which consider ergonomics and physical properties,
the most recognized being the keyboard designed by
August Dvorak The Dvorak keyboard was developed
on the basis of studying finger motion and lettering
combinations which were easier and more efficient
to execute, and incorporating them into new keyboard
character arrangements A number of variations of
this by other people have also been called Dvorak
keyboards, even when they differ from that developed
by A Dvorak
Unlike typewriters, it's easy to remap key positions
on computer and alternate keyboards can be designed
to put the letters anywhere the user desires In spite
of this, QWERTY keyboards remain prevalent, and
manufacturers and teaching institutions are reluctant
to change to other systems
Qwest Communications A telecommunications
company establishing fiber optic networks in over
100 U.S and Mexican cities Commercial services provided include dedicated business Internet access, Internet faxing, Internet phone (Q.talk), and video
In June 2000, Qwest Communications International Inc completed a merger with U.S West, Inc an-nouncing an $85 billion market capitalization with services in 14 states In October 2001, Qwest and its principal shareholder, Anschutz Company, an-nounced plans to purchase 14 million and 6 million shares, respectively, of the Netherlands company Koninklijke KPN N.V The company further an-nounced plans for acquiring Global TeleSystems, Inc., to embark on a significant European expansion
QZ billing A telephone subscriber service in which
the time and charges for an outgoing call (usually a toll call) can be obtained from the phone company This is especially useful for business professionals and educational institutions that bill back to the call-ing department QZ billcall-ing is becall-ing superseded by automated call accounting information
QuickTime Applications
Application Description
QuickTime 3D Apple Computer's 3D QuickTime cross-platform 3D rendering software
QuickTime Conference QTC Designed on Apple Computer's QuickTime compression technology,
QuickTime Conference supports videoconferencing in a window on the com-puter screen Electronic whiteboarding is also supported, so participants can communicate and collaborate on shared drawing, text, or other projects The software can be used to deliver Web events using QuickTime Live! software See Simple Multicast Routing Protocol
QuickTime Player A software application for playing back audio and video files created by
QuickTime Pro authoring software and other applications that export the QuickTime Pro authoring file format QuickTime 5 has support for skip pro-tection for streaming sources with uneven video delivery, media "skins" to enable the user to customize the look of the player, Internet TV channel dis-play and audio control features, and support for plugins from Apple and third-party developers
QuickTime Pro A low-cost, commercial authoring system for creating QuickTime
multime-dia images and presentations It SUpp0l1S many popular file formats that may
be played on freely-downloadable QuickTime Player programs
QT Streaming Server Anextension to QuickTime to deliver realtime multimedia over the Internet
using the Real-Time Transport Protocol/Real-Time Streaming Protocol (RTP/ RTSP) Thus, it can deliver video-on-demand and, when combined with broadcasting software, live streaming news, interviews, or entertainment through a network QuickTime Streaming Server is available in Macas x
Server and the Darwin Streaming Server is available through the Darwin open source project The Streaming Server is available on a variety of platforms and the open source software makes it possible to port to additional platforms The software provides Web-based server configuration, TCP-based broad-cast support, skip protection, and other features
QuickTime VR Anextension to QuickTime that adds cross-platform virtual reality
capabili-ties through a movie-like presentation of images The user can move through the scene, pan the surroundings, interact with objects, and much more Quick-Time Authoring Studio can be used to create virtual reality scenarios for dis-play in QuickTime YR QTYR Make Cubic enables users to build Cubic Vir-tual Reality software
Trang 6R 1.symb.range 2.symb.resistance See resistance.
R interfaceInISDN, a number of reference points
have been specified as R, S, T, U, and V interfaces
To establish ISDN services, the telephone company
and ISDN subscriber typically have to install a
num-ber of devices and links to create the all-digital
cir-cuit connection necessary to send and receive digital
voice and data transmissions
The R interface is the portion of the link between an
ISDN terminal adapter (TA) on the customer
pre-mises, and customer non-ISDN station equipment
(TE-2) such as phones, facsimile machines,
comput-ers using modems, etc Some communications
de-vices are being manufactured with ISDN terminal
adapters built in, in which case, the R interface is not
needed (or is considered to exist inside the
compo-nent itself) See ISDN interfaces for a diagram
R reference pointInISDN, the point in the digital
communications path at which non-ISDN TE-l
de-vices connect to a Terminal Adapter (TA) See R
in-terface
R Series RecommendationsA series oflTU-T
rec-ommended guidelines for radio systems, operations,
and spectrum use These guidelines are available for
purchase from the lTU-T Since lTU-T specifications
and recommendations are widely followed by
ven-dors in the telecommunications industry, those
want-ing to maximize interoperability with other systems
need to be aware of the information disseminated by
the lTU-T Afull list ofgeneral categories is listed in
Appendix C and specific series topics are listed
un-der individual entries in this dictionary, e.g., S
Se-ries Recommendations See R SeSe-ries
Recommenda-tions chart
R-Y red-luminance In the YUV video color model
in which chrominance and luminance are separate,
the color R (red) minus Y (luminance) equals V,
which is used to calculate color differences
Associ-ated with this is the color B (blue) minus Y
(lumi-nance) equals U Ifboth calculations were to be zero
(0), it would indicate no color (chrominance)
Invideo engineering, R-Y (red -luma) andB-Y (blue
-luma) are multiplied by defined values to deriveV
and U, respectively Color difference components
with luma removed are represented as R' -V' and
approach to decomposing a YUV video signal that is useful for a variety of reasons, including as a means
to reduce bandwidth for transmission and for special effects It is used in the PAL analog video standard and CCIR 601 digital video standard
RlT 1 See realtime 2 receive/transmit
RIW read/write
R&D See research and development
R&E 1 See Research and Education 2 research and engineering
R&Sresearch and statistics
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RlsignalingA type ofsignaling scheme commonly
usedinchannelized voice networks in North America
and Japan that is typically implemented through a Tl
line It enables supervisory and address signals to be
transmitted between network switches using a single
frequency for supervisory (line) information and
multiple frequencies for address (register)
informa-tion Tl signaling is specified in ITU-T
recommen-dations Q.310 to Q 331 See channel-associated
sig-naling, R2 signaling
R2signalingAtype ofsignaling scheme commonly
used in channelized voice networks outside North
America and Japan In association with E1networks,
it is similar to channelized T1 R2 implementations
tend to be variants ofITU-T Q.400 to Q.490
recom-mendations; there is some flexibility in the
chan-nelized signaling parameters for setting the
param-eters for specific countries, an important capability
inthe multicultural European Union Signal types are
configured as line signals and interregister signals
See channel-associated signaling, RI signaling
RA 1 radar altimeter 2 rate area A region
desig-nated to receive products and services at described
rates for the purposes of administration and billing
3 See RealAudio 4 Reliability Action Center
RA numberSee return authorization number
RA-ENSee Radio Amateur Emergency Network
RAC 1 See Radio Amateurs of Canada 2 Radio
Austria Communications Based in Vienna 3 See
re-mote access concentrator
RACE1 random access computer equipment 2 See
Research in Advanced Communications in Europe
RACESSee Radio Amateur Civil Emergency
Ser-vice
racewayAduct or channel system designed to hold,
protect, and direct interior wiring circuits Raceways
are typically plastic or metal modular construction,
with a variety of fittings so individual sections can
be interconnected and holes can be punched where
needed Raceways can be mounted on or in walls or
floors See molding raceway
RACF1 See Radio Access Control Function 2 See
resource access control facility
rack, trayA support structure designed for the easy
insertion, removal, and configuration of modular
component systems Racks are frequently equipped
with rollers, although large ones may be attached to
a wall for better support They are generally
as-sembled from rigid metal strips, interconnected to
produce a strong open structure so the components
can be quickly slid in and out of the individual bays
from the front, and cabled to one another at the back
Racks are commonly used in the broadcast TV and
video editing industries; they can also be found in
telephone switching installations and on large
com-puter networks with a variety of storage media See
distribution frame, rack unit
rack mountableA component designed to
specifi-cations so it will fit easily and securely into a storage
and support rack of a standard size for components
from that industry See rack, rack unit
rack unitRU Ameasure ofdistance based on
physi-cal rack structures that are common within various industries Rack sizes have long been standardized
in the power distribution, audio/visual, and portions
of the retail sales industries
Racks are especially common for supporting video processors, frame synchronizers, frame grabbers, and other video editing and broadcast components In the video industry, the rack width for rack-mountable audio and video components is typically 19in.and the vertical rack unit (RU) is 1.75 in Thus, a 3.5-in.-high component would be described as having a height of2RU See rack
raconSee radar beacon
RACS1 remote access calibration!controVcomput-ing services/system
RACTremote access computer/control terminal radradiation absorbed dose A quantification of ra-diation energy that describes how much rara-diation is delivered to 1g ofa substance by 100 ergs ofenergy Radiation absorbed by body tissue is measured in roentgens
RAD 1 rapid application development/design 2 See Radiance 3 random access device 4 recorded an-nouncement device 5 remote antenna driver radarradio detection and ranging.In its basic form, radar is a means of detecting distant or unseen ob-jects by emitting radio frequency electromagnetic waves and measuring the reflected response As such
it can operate at night, during fog, and in situations where something is too distant to be seen by unaided eyes Radar works on the principle that radio waves will deflect off of solid or sufficiently dense objects
in a way that can be anticipated or controlled so the returning signal can be analyzed for the presence of the objects, their general shape and size, and their distance Radar is a powerful and flexible technol-ogy that has become an intrinsic aspect ofnavigation, reconnaissance, and imaging systems
Radar typically operates in ultra high frequencies (UHF) and microwave frequencies See radar, his-tory; sonar; Taylor, A.H
radar, historyRadar and sonar originated in much the same way in the late 1800s and the two technolo-gies still share many terms and general principles Johann Christian Doppler (1803-1853) made impor-tant contributions to both radar and sonar history by studying the way in which compressions arising from motion could alter sound frequencies, relative to the position ofthe viewer (or sensing instrument) It was discovered that this characteristic was also applicable
to electromagnetic phenomena like radio waves and light, resulting in Doppler radar technologies about
100 years later
The fact that electromagnetic waves could be re-flected was first demonstrated by Heinrich R Hertz (1857-1894) in 1886 In 1904, Christian Hiilsmeyer (1881-1957) patented a "far-moving scope" which used reflected radio waves (early radar) for detect-ing marine vessels in order to prevent collisions at sea, a system that eventually superseded searchlights for detecting nearby vessels in the dark or fog In
1906, William R Blair described the use of
Trang 8electro-ergy returning from various reflecting surfaces By
1916, interest in radio sensing devices was
spread-ing rapidly Dominik and Scherl had invented a
ra-dio echo sensing device in Europe and in 1917 Nicola
Tesla wrote about radar concepts in theElectrical
Experimenterin America
The earliest commercial use of radio frequencies for
bouncing signals was in the 1920s and 1930s, where
it was used to determine the presence of marine
ves-sels and aircraft to help prevent collisions By the
mid-1930s, when cathode-ray tube displays were
becoming commercially viable, radar was used in
both military and commercial navigation and
docu-mented in engineering textbooks With the onslaught
of World War II, interest in radar increased
dramati-cally and substantial resources were devoted to its
im-provement and adaptation for military purposes
Since then, radar has been adapted to many
indus-tries and continues to be used for its original purpose,
navigational safety, and for many diverse military and
commercial applications See radar
radar beaconA device associated with a particular
location or object that is capable ofemitting a
radar-range radio signal to indicate its geographic location
Apassiveradar beacon is one that sends out a
ra-darsignal from time to time that can be sensed
by an appropriately tuned radar receiver
within range However, it does not have a
re-ceiver and cannot detect whether a radar
sig-nal has been aimed in its direction
Anactiveradar beacon includes both a radar
re-ceiver and a radar transmitter The rere-ceiver
en-ables the beacon to sense a triggering pulse
from a remote radar that causes the beacon to
broadcast a returning signal or a series of
re-turning signals The information contained
within the signal depends upon the system
used, but can provide range, bearing, and,
op-tionally, identification information
Because radar technology tends to be expensive,
ra-darbeacons are more often installed in industrial
ship-ping facilities and military applications than in
con-sumer devices Sometimes they are used in
light-houses
Some less expensive radar beacons do exist, however,
in the form ofpolice speed detectors The speed
de-tector determines a vehicle's speed by sending out a
radar pulse that essentially acts as a beacon to any
suitably tuned automobile radar detection units within
range
radar detector Adevice designed to detect the
pres-ence of radar-range radio signals These are used in
military applications to detect or interpret radar-range
communications They are also sold for civilian use
in the form ofcar-mountable devices to detect police
speed-detection radar systems The use of radar
de-tectors is regulated and prohibited in some areas See
radar, radar beacon
radar screen/scopeA small display device, usually
round or rectangular, which shows target signals as
other alignment and location marks superimposed over the illuminated blips on the screen to aid in track-ing and location The term radar "scope" comes from the early days when cathode-ray tubes (CRTs) were being adapted for use as oscilloscopes and various types of radar screens See radar
radar systemsDevices incorporating radio waves to detect the presence and characteristics of distant or otherwise unseen objects Although radio echoes were observed in the 1920s and put into practical use
in the 1930s, developments in radar guidance, detec-tion, and identification systems did not flourish until the second World War See cavity magnetron RADARSAT A Canadian satellite system launched
in November 1995 The satellite supports a synthetic-aperture radar sensor that can deliver data in seven sizes based upon 25 beam positions Images vary, depending upon the way the sensors are angled and the Earth viewed Each beam position has a specific elevation angle and size The two beam modes are single beam and multiple-beam ScanSAR RADARSAT is part of the RADARSAT Network System
Radar Scope
Much attention has been given to the development
of radar technologies for navigation and military tracking purposes This radar scope, on board a u.s.
aircraft carrier, is usedfor aircraft approach control Civilian and military air traffic controlpersonnel en-sure the safe and orderly flow of air traffic in com-mercial airports and on military vessels at sea This photo was taken during NATO Implementation Force (IFOR) patrols ofthe waters ofthe Adriatic Sea The U.S Air Force C-14B aircraft was the first to use ground-based radio beaconsfor a completelyau-tomated landing in August 1937 The system offive transmitting beacons used to accomplish thisfeat was developed by Carl J Crane [Detail ofDoD photo by
J Hendricks, U.S Navy.J
radial accelerationAcceleration in a circular traj ec-tory, characteristic of a spinning solid or liquid
Trang 9Fiber Optics Illustrated Dictionary
substance Radial acceleration is used in centrifugal
separators to isolate particular particles or substances
The radial acceleration characteristics ofvarious
spi-raling entities are ofinterest to astronomers In
opti-cal media, radial acceleration is one of the
charac-teristics measured to determine conformance with
ex-pected properties or standards, along with axial
ac-celeration and radial ronout
RadianceRAD Anative file format for Radiance, a
public domain Unix-compatible radiosity rendering
engine The file extension rad may be used to
dis-tinguish RAD files
radiant energyTransmitted electromagnetic energy
such as heat, light, or radio waves Radiant energy is
typically measured in calories, ergs, or joules
radioAnappliance or other device designed for the
transmission and/or receipt ofradio wave
communi-cations There are many types of radio technology:
amplitude modulation (AM), frequency modulation
(FM), shortwave, cellular, short-range (cordless
phones, wireless intercoms), etc With increased
de-mand for wireless communications, harnessing and
using radio waves efficiently has become extremely
importantinboth scientific and commercial research
More details about radio communications can be
found under individual listings in this dictionary See
crystal detector, detector
RadioThe publication name ofa widely-distributed
Soviet electronics journal which, in June 1957,
an-nounced the Soviet Union's plans to soon launch a
satellite ("sputnik" in Russian), and provided details
of the planned launch date, modulation techniques,
and frequencies to be used Sputnik I did in fact
launch at the end of that year See SputnikI
Radio Access Control FunctionRACF.Ina
PACA-E Personal Communications System (PCS), the
RACF intercommunicates with a number of entities
while handling the service logic, including the
Ra-dio Control Function (RCF) and the Call Control
Function (CCF)/Service Switching Function (SSF)
See Priority Access and Channel Assignment
Radio Act of 1912With increasing interest in radio
broadcasting and demand on airwaves, the U.S
Con-gress passed an act which granted the U.S
Depart-ment ofCommerce the authority to regulate amateur
broadcasting in order to prevent interference with
government stations and to increase maritime safety,
largely due to the sinking oftheTitanic See TItanic.
Radio Act of 1927As a response to the enormous
rising demand for broadcast channels in the early part
of the century, a conference was held to sort out the
chaos As of the Radio Act of 1912, the U.S
Depart-ment of Commerce took control of radio
broadcast-ing Zenith Radio Corporation applied for a license
to operate at a frequency that was being used by other
stations as well, and so was granted a license to
broad-cast at a different frequency Zenith changed
frequen-cies to one that had already been granted, instead of
using the one that had been licensed In the process
of investigating the violation, it was found that the
Department of Commerce didn't have sufficient
ju-risdiction to stop the actions of the broadcaster, and
one of the consequences was the creation of the Fed-eral Radio Commission (FRC) in1927.This was later
to become the Federal Communications Commission (FCC) through the Communications Act of 1934 See Communications Act of 1934, Federal Communica-tions Commission
Radio Amateur Civil Emergency ServiceRACES Apublic emergency service provided by reserve vol-unteer communications personnel to assist regular emergency services in times of extraordinary need The organization was established in 1952 Planning guidance for RACES deployment is provided by the Federal Emergency Management Agency (FEMA) http://www.races.net/
Radio Amateur Emergency Network Raynet Raynet was established as a result of a violent storm that pummeled the eastern coast of England in Janu-ary 1953 Coastal towns and villages were ravaged and more than 300 drowned Since telephone lines were destroyed as well, there was no reliable com-munication into or out of the area during the storm The police authorities appealed to radio amateurs to help and the Home Office gave permission for ama-teur radios to coordinate rescue services, saving many lives Thus RA-EN was born, and grew in capabili-ties in 1989 when legislation restriction was lifted to enable the organization to provide greater help It is now known as Raynet
Radio Amateur Satellite Corporation RASC, AMSAT-NA This is the North American branch of the international amateur radio satellite community,
a not-for-profit agency founded in 1969
Over the decades, radio amateurs have made signifi-cant contributions to the evolution ofsatellite broad-casting technologies in spite ofthe budget constraints typical of amateur organizations AMSAT-NA sup-ports and promotes scientific research and develop-ment in radio communications satellites and space science in the public interest The air waves, by legal right in the U.S., belong to the people, and radio ama-teurs are exercising not only their right to use this wonderful resource, but have furthered theart ofwire-less communications in countofwire-less ways AMSAT has successfully launched more than two dozen noncom-mercial radio communications satellites into Earth orbit since the historic OSCAR satellites of the early 1960s See AMSAT, OSCAR http://www.amsat.org/ Radio Amateurs of CanadaRAC RAC provides liaison, coordinating functions, and policy decisions for the benefit of Canadian amateur radio organiza-tions and individual amateur radio operators http://www.rac.cal
radio broadcastingCommercial radio broadcasting began in the early 1900s, arising out of the experi-mental broadcasts of inventor R Fessenden in 1906 There were many amateur broadcasts between 1906 and 1920, including the regularly scheduled shows
by Charles "Doc" Herrold, at the Herrold College of Wireless and Engineering in California, and the pre-KDKA broadcasts from the garage of F Conrad in
1919 CFCF and KDKA are acknowledged as the first commercial stations, beginning in 1920
Trang 10by 1913, and the Eiffel Tower still stands as a
his-toric reminder ofthe lofty ambitions ofthe broadcast
pioneers It was built for the Paris World's Fair in the
1800s and there have been several attempts to remove
it since then, but its usefulness as a giant antenna is
one of the reasons it was preserved Lee de Forest
participated in one ofthe first transcontinental
broad-casts from the world's largest radio tower The
Ra-dio Corporation ofAmerica (RCA), founded in 1920,
is one of the best known and most influential of the
early radio pioneers, and much ofits history is related
to the activities of David Sarnoff Sarnoff was also
instrumental in forming the National Broadcasting
Corporation (NBC), in 1926 The following year the
Columbia Broadcasting System (CBS) was formed
(originally Columbia Phonograph Broadcasting
un-til William S Paley bought out the company in 1928)
From 1921 to 1922 the number of commercial
sta-tions in the U.S increased from five to over 500 In
the early 1930s, record companies became nervous
about competition from radio stations and began
re-stricting the open broadcasting of audio recordings
From that point on, royalties and other means of
en-forcing payment for broadcasts were instituted
By the late 1930s the wonderful music from bands
and orchestras around the world could be heard
through the magic of radio, and listeners who had
never been to a theater to hear a live performance
enjoyed the new form of entertainment The advent
of radio meant the eventual death of vaudeville, but
some of the vaudevillian actors, perhaps best
exem-plified by George Bums and Gracie Allen, made a
successful transition to radio, and eventually to TV
programming
By the early 1940s, frequency modulated (FM)
broadcasting, made possible by the tireless efforts of
inventor Edwin Armstrong, was beginning to catch
on and, while it didn't supersede AM, it provided
clean, clear transmissions that were favored by
pub-lic broadcast and classical music stations The
inven-tion of the transistor created a revoluinven-tion in
minia-turization and manufacturing By the 1950s, radio had
competition from TV broadcast stations, but unlike
many technologies, it didn't lose its practicality and
appeal Radio stations in North America still
outnum-ber TV stations, and radio sets continue to be in
de-mand
The next major milestone in radio broadcasting came
with Sputnik and the exploration of space In 1969,
American astronauts sent sound and images from the
Moon to Earth Soon communications satellites were
being launched into orbit in the 1970s and 1980s This
provided a means to develop mobile
communica-tions, and linked computers and radios as never
be-fore Many ofthe pioneer communications efforts and
new technologies were contributed by amateur radio
enthusiasts, most notably through the OSCAR and
AMSAT satellite programs
With digital electronics, laptops, and cell phones, the
importance of radio continued to grow, as wireless
communications were integrated into increasingly
in radio broadcasting is the introduction of digital broadcasting, pioneered by Sweden in 1996 See AMSAT; ANIK.; CKAC; Emergency Alert System; KDKA; OSCAR; Radio Corporation of America; Sarnoff, David; radio history
radio broadcasting regulationsMany different sets ofguidelines and regulations have been developed to manage radio broadcasting Some of these were in-tended to curtail unfair business practices, such as more powerful transmitting stations deliberately drowning out less powerful ones, and some were implemented to organize and coordinate the use of limited airspace, that is, the limited availability of broadcast frequencies Others were put into effect in wartime to shut down broadcasting almost entirely, curbing the broadcast pirates, but also curbing respon-sible amateurs In 1963 the Emergency Broadcasting System (EBS) was established, recently replaced in
1997 by the Emergency Alert System (EAS) Several Radio Acts and later Telecommunications Acts have controlled American broadcasting over the decades The jurisdiction has changed hands a num-ber of times, from the u.S Secretary of Commerce
to the Federal Radio Commission (FRC) in 1927, to the Federal Communications Commission (FCC) in the mid-1930s The FCC has retained its wide-rang-ing licenswide-rang-ing and regulatory powers up to the present time See Emergency Alert System, Federal Commu-nications Commission, Radio Act of 1912
radio button Aphysical button on a component, or iconic button in a software program, which permits selection of only one option from a group of mutu-ally exclusive selections Selecting anyone option automatically deselects the previous option The name derives from the action of pushbutton radio sets in which buttons can be pretuned to selected stations, and then pushed for the desired station, one at a time Software radio buttons are often seen on input forms
on Web pages
Radio Club ofAmericaThis historic amateur radio group is still operating after its birth in the early 1900s
Itheld its first meeting in 1909 and was founded as the Junior Wireless Club Limited in 1910 in New York City The organization changed its name the follow-ing year to the Radio Club of America The young members of the club successfully lobbied for the in-terests of amateur radio enthusiasts before the U.S Senate Commerce Subcommittee The first official meeting of the organization under its new name was
in November 1911 As it grew, some of the great names in radio history became associated with the club, including Paul Godley, Edwin Armstrong, and David Sarnoff It exists for the charitable, educational, and scientific furtherance of radio communications and provides scholarship funds for needy and wor-thy students of radio communications See Junior Wireless Club Limited
http://www.radio-club-of-america.org/
Radio Common CarrierRCC Service providers of mobile telephone and paging services employing ra-dio technology, as opposed to land line transmissions