In a PACA-E Per-sonal Communications System PCS, the point to-wards which Radio Terminal Function transmissions are directed and from which the RTF interacts with other network entities
Trang 1Fiber Optics Illustrated Dictionary
Radio Communication Laws of the United States
The sinking of the Republic and the Titanic, in
addi-tion to the Internaaddi-tional RadioTelegraphic
Conven-tion, were strong factors in the development
ofAmeri-can regulations for radio communications In 1910
and 1912, U S acts were approved resulting in the
publication ofthe Radio Communication Laws ofthe
United States and the International Radiotelegraphic
Convention,by the U.S Department of Commerce
Bureau of Navigation Radio Service, in 1914 This
document described the major international
agree-ments and U.S radio regulations and guidelines and
spelled out the requirement for any steamer
navigat-ing U.S waters carrynavigat-ing 50 or more persons to be
" equipped with an efficient apparatus for radio
communication capable of transmitting and
re-ceiving messages over a distance of at least one
hundred miles, day or night An auxiliary power
supply, independent of the vessel's main electric
power plant, must be provided which will enable
the sending set for at least four hours to send
mes-sages over a distance ofat least one hundred miles,
day or night, and efficient communication between
the operator in the radio room and the bridge shall
be maintained at all times
The radio equipment must be in charge oftwo or more
persons skilled in the use of such apparatus, one or
the other ofwhom shall be on duty at all times while
the vessel is being navigated "
The document further described licensing
require-ments for amateur and commercial operators,
stipu-lated the designation of certain definite wavelengths
as normal communications frequencies for a station,
and standardized SOS (dot-dot-dot dash-dash-dash
dot-dot-dot) in Morse Code as the official distress
call, in addition to other basic tenets of radio
com-munications See International Radiotelegraphic
Con-vention
Radio Control Function RCF In a PACA-E
Per-sonal Communications System (PCS), the point
to-wards which Radio Terminal Function transmissions
are directed and from which the RTF interacts with
other network entities in the processing of a
PACA-E (priority access) call See Priority Access and
Chan-nel Assignment
Radio Corporation of America RCA.Anoffshoot
of General Electric founded in 1919 as a result of a
merger with the Marconi Wireless Telegraph
Com-pany of America In 1920, RCA made a significant
agreement with WSA, AT&T, GE, Westinghouse, and
others, to be the exclusive distributor ofradio
receiv-ing sets and crystal detectors.In1921, David Sarnoff
joined the company as its general manager, and later
moved up in the corporation, becoming vice
presi-dent in 1926 Sarnoff was a colorful part of its
his-tory for many decades See Armstrong, Edwin
Howard; Sarnoff, David
radio facsimile The transmission of the contents of
pages including text and images by means of radio
signals Radio facsimiles were pioneered in the 1800s,
and this early form of facsimile machine was in use
at least as early as 1943 See facsimile
radio frequency RF Radiant electromagnetic waves that range from about 3 to 10kHz at the lowest end
to just about 300 GHz at the high end, a position that falls between the audio frequencies and the bound-ary of the visible spectrum where infrared is found Radio frequencies are widely used for radio and tele-vision broadcasting, and for various types of wire-less communication The frequency range has been administratively subdivided into a number ofcatego-ries so that limited airwaves can be assigned and li-censed in an efficient way In the U.S., this responsi-bility is managed by the Federal Communications Commission (FCC); in Canada it's managed by the Canadian Radio Television and Telecommunications Commission (CRTC) See band allocations for chart radio history Radio history is one of the most inter-esting histories in technology As soon as humankind discovered that communications could be transmit-ted at the speed oflight, they enthusiastically sought ways to achieve practical embodiments ofthe possi-bilities The gradual discovery and harnessing ofelec-tromagnetic frequencies to carry meaningful commu-nications changed society in fundamental ways and radio waves have since been developed for a bewil-dering variety of technologies, from interstellar te-lemetry to radar range ovens that almost instantly cook food
The earliest radios were low-power crystal detectors that exploited the oscillating properties ofnatural and synthetic crystals to "capture" (resonate with) radio waves and transmit the signal to earphones worn by the listener This wasn't a very easy way to share ra-dio communications with a room full of people, so improvements for increasing the sound volume and the development of antennas to intercept the signals were pursued by radio inventors The significant his-tory of modem radio technology starts with Lee de
Forest's invention ofthe Audion, a three-element
elec-tron tube derived from Fleming's two-element tube The addition of the third element was highly impor-tant, as it enabled the flow of electrons to be con-trolled which, intum,made it possible to build radio signal amplifiers for hundreds of different applica-tions De Forest claims he made voice broadcasts from New York around 1906 In 1916 he gained no-toriety for broadcasting incorrect election results One of the uncredited pioneers of radio history was inventor Valdemar Poulsen He is well known for his contributions to telegraphy and tape recording tech-nologies, but most people are unaware that he broad-cast music from the town of Lyngby, on March4,
1909, by putting a microphone near a gramophone player The radio transmission was received by 16-year-old Einar Dessau on his home-made amateur radio receiver in Hellerup
With the development of practical methods of radio broadcasting, creative minds quickly grasped the so-cial, cultural, military, and commercial applications ofradio communications Experimental radio stations sprang up everywhere beginning around 1910 with many early broadcasts sent in Morse code Consumer radio sets, called "talking machines," gradually
Trang 2Guglielmo Marconi was a young, ambitious
inven-tor who became a prominent radio pioneer He was
the first to develop many radio technologies and the
first to use or adapt many technologies developed by
other all:but-forgotten inventors
Atrue broadcasting pioneer, Doc Herrold began
trans-mitting in 1909, the same year as Poulsen, and made
history by airing music and news to the 1915 World's
Fair In 1916, he received callsign 6XF from the U.S
Department of Commerce At about this time, Lenin
began using radio to reach the public in Russia while
Marconi set up broadcasting in Europe and North
America Wartime restrictions hampered
broadcast-ing around this time but didn't stop the evolution of
radio In Montreal, Canada, Marconi's station XWA
received an experimental license in 1918, a general
license in 1919, and broadcast its first regularly
scheduled musical concert in May 1920 XWA
evolved into CFCF in November 1920 Station
KDKAin Pittsburgh (under its original 8Xk callsign)
broadcast election events in November 1920
No doubt there are many uncredited radio pioneers
as early callsigns were self-assigned, the technology
was loosely regulated, and few listeners existed to
credit the true pioneers From the 1920s onward,
how-ever, regulated radio broadcasting flourished,
mak-ing it easier to unravel and confinn its history
Historic Presidential Radio Communication
President Herbert Hoover listening to an early
elec-tron tube-based radio set, around 1925 Hoover and
Coolidge were two of the first presidents to exploit
the informational andpoliticalpotential ofradio
com-munications [Library o/Congress American Memory
National Photo Company Collection.]
Calvin Coolidge was quick to exploit radio
technol-ogy in the U.S in the 1920s, for political
communi-cations, as was Vladimir Lenin in Russia Radio is
now an inextricable aspect ofpolitical campaigns and
communications and is used by government agencies
for coordination, national security, and emergency
services
radio broadcasting
The importance of the development of transistors at the Bell lab in the late 1940s cannot be overstated
Transistors not only made it possible to shrink build-ing-sized computers down to the size of a large pho-tocopier, but enabled portable radio technologies and mobile communications technologies to evolve and flourish from the 1950s onward The semiconductor industry further enabled hardware engineers to com-bine many functions on a single chip, increasing pro-cessing speeds and reducing component sizes even further Radio is still a highly significant communi-cations technology, which is now being incorporated into telephones and other traditional wired devices
The evolution of the technology is ongoing See Audion, CFCF; Conrad, Frank; crystal detector;
Herrold, Doc; KDKA; Marconi, Guglielmo; Tesla, Nikola; telegraph history; XWA
Radio Link ProtocolRLP, RLP 1 A protocol stan-dardized by the TelecommunicationsIndu~try Asso-ciation (TIA), in the mid-1990s, using SDI, a fonnal specification language RLP is a data link layer cir-cuit-mode protocol for connecting a Mobile Tenni-nal (MT) with a Mobile Base Station (MBS) to pro-vide a stationary digital radio interface through a pub-lic switched telephone network (PSTN) to another data-compatible telephony device This makes it use-ful for cellular data transmissions applications
Radio Technical Commission of Aeronautics RTCA, Inc Aprivate, not-for-profit corporation pro-moting consensus-based recommendations for com-munications, air traffic management, navigation, and surveillance issues The RTCA was established in
1935 It now represents morethan270 trade, academic, and governmental organizations The RTCA includes prominent names in the aviation industry, including the National Business Aviation Association, NASA, the National Air Traffic Controllers Association and various international airlines, and pilot associations
It makes recommendations to the Federal Aviation Administration(FAA)(also a member)
http://www.rtca.org/
Radio Terminal FunctionRTF.Ina PACA-E Per-sonal Communications System (PCS), the RTF is the point from which the PACA-E subscriber accesses the mobile communications network Communica-tions are directed from the RTF towards the Radio Control Function (RCF) through which it can inter-act with other network entities See Priority Access and Channel Assignment
radio waveAnelectromagnetic wave, commonly
used to carry audio transmissions, in a frequency spectrum that ranges from 10KHz to 200 GHz Trans-mission waves such as radio waves are further clas-sified into subcategories according to various prop-erties; examples include ionospheric waves (sky waves), ground waves, short waves, and others The characteristics of various transmissions media, chiefly the Earth's ionosphere, are exploited to aim and propagate these waves Frequency divisions of radio waves according to wavelength (higher
' F ,;;t:
•.
';.>.~.~.'::.
,',
Trang 3Fiber Optics Illustrated Dictionary
frequencies have shorter wavelengths) have been
des-ignated as shown in the chart under band allocations
Sounds and other signals are converted to radiating
waves for transmission, then converted back at the
receiving end See antenna, ionospheric wave, ground
wave, radio, short wave
Radio-Television News Directors Association
RTNDA.Aninternational nonprofit professional
or-ganization of network and local news executives in
the broadcasting, cable, and multimedia industries
Established in 1946, the RTNDA promotes high
stan-dards of electronic journalism, the exchange of
knowledge among members, public understanding of
the profession, and journalistic freedom It sponsors
an annual international conference for professionals
in the news industry http://www.rtnda.org/
Radio-Television News Directors Foundation
RTNDF Affiliated with the Radio-Television News
Directors Association, the foundation promotes
ex-cellence in electronic journalism through research and
educational programs for news professionals and
stu-dents of journalism The work of the Foundation is
supported by other foundations, corporations, and
RTNDA members Research results of interest are
posted or summarized on the RTNDA Web site
radiogram1 A telegram sent through
radiotelegra-phy, also called "radiograph." See telegram 2
Com-bined radio receiver and phonograph
radiometerA device for measuring the intensity of
electromagnetic radiation, which may include visible,
UV, or infrared light and emanations beyond the
op-tical spectrum Aphotometer is a type of radiometer
specialized for the measurement of light intensity A
spectroradiometer further enables color assessment
by analyzing the spectral range or specific wavelength
of sampled light in addition to measuring radiant
in-tensity
For scientific understanding and high precision
ap-plications, various research scientists and standards
bodies have sought to derive absolute or reference
measures for luminous intensity, luminous flux, and
illuminance Agoniophotometric detector calibrated
against the realized luminous intensity standard can
be used to establish a unit of luminous flux A
simi-lar instrument with a charge couple detector (CCD)
may be used with standard intensity lamps to
detenninance luminance See photometer
radiometeorographSee radiosonde
radiophoneA device that transmits sound through
radio waves Although the tenn is less common,
ra-diophones are everywhere; they have more individual
names now due to their specialization (cordless
phones, cell phones, etc.)
radiosonde, radiometeorographAminiature,
auto-matic radio transmitter usually sent aloft on an
air-craft or meteorological balloon, to transmit back
meteorological information, such as temperature,
humidity, pressure, etc
radiotelegraphyTransmission of telegraph signals
through radio waves The carrier wave was modulated
to carry Morse code The two main types were
con-tinuous-wave (CW), in which the carrier wave was
interrupted to fonn the coded symbols, and inter-rupted continuous-wave (ICW), in which the carrier was modulated at a fixed frequency
radiotelephonyThe art and science ofcommunicat-ing through radio waves, often by means of various types ofradiophones
RADIRrandom access document indexing and re-trieval
RADIUS ProtocolRemote Authentication DialIn User Service A client/server network protocol for carrying authentication, authorization, and configu-ration information between a Network Access Server (NAS) (a client), desiring to authenticate its links, and
a shared authentication server RADIUS was submit-ted as a Standards Track RFC by Rigney et al in June 2000
A RADIUS client passes user information to desig-nated RADIUS servers and acts upon the responses The server receives connection requests and authen-ticates the user, returning all configuration informa-tion needed for clients to deliver services to the user
A RADIUS server may act as a proxy client to other servers
Authentication transactions are handled as "shared secrets" that are not transmitted over the network Any transmitted user passwords are encrypted and RADIUS can work with a variety of authentication schemes (e.g., CHAP) The officially assigned port number for RADIUS messages has been changed from 1645 to 1812 See RFC 2865, which obsoletes RFC 2138 See RFC 2868 for RADIUS support for compulsory tunneling and RFC 2869 for RADIUS extensions
RADIUS Accounting Protocol Anadministrative client/server protocol used in conjunction with RA-DIUS Authentication and Authorization services to deliver accounting information from a Network Ac-cess Server (NAS) to a RADIUS accounting server The RADIUS accounting server receives an account-ing request associated with a database of users of a modem pool, for example It returns an acknowledg-ment of the user request The RADIUS Accounting server may act as a proxy client to other types of ac-counting servers, as well
RADIUS Accounting was submitted as an Informa-tional RFC by C Rigney in June 2000 The officially assigned port number for RADIUS Accounting has been changed from 1646 to 1813 See RFC 2866, which obsoletes RFC 2139 See RFC 2867 for modi-fications for Tunnel Protocol support See RADIUS Protocol
RADLradio laboratory 2 See Reticular Agent Defi-nition Language
radomeA radar "dome," a housing around a radar antenna which protects it without interfering with the signals Radomes are especially important in radar antennas exposed to the elements, as in an airplane
RADSLSee Rate Adaptive Digital Subscriber Line RAF Royal Air Force
RAI remote alarm indication
RAID See redundant array of inexpensive disks RAIN See redundant array of independent netports
Trang 4raised floor distributionAtype ofstructure designed
to accommodate a horizontal distribution frame for
the attachment and management of wiring
installa-tions It is typically designed so that the floor
cover-ing can be pulled aside or lifted to gain access for
changes or additions See distribution frame
RAM See random access memory
RAM diskAnarea of chip memory allocated and
managed as though it were a disk drive Unlike a disk
drive, RAM is volatile; it requires a continuous source
of power to retain its information and will lose the
stored data ifthe system is turned off ARAM disk is
a means ofdisk caching that was popular when many
systems had only floppy drives and no hard drives
It provided a fast way to access data without doing
disk seeks or swapping out disks RAM disks are now
less prevalent
RAMMobile DataAnopen architecture, nationwide
commercial data communications service offered by
Ericsson, BellSouth, and RAM Broadcasting It is
similar to ARDIS, a packet data service offered by
Motorola Base stations are used for relaying
mes-sages to users or to other stations
RAMAC Random Access Memory Accounting
Ma-chine A historic large-scale computing machine
an-nounced by ffiM, in 1956, for plant automation
ac-counting and data processing applications It included
magnetic disk memory with a capacity of 5 million
digits Results of computations were recorded on
punch cards Over 1000 RAMACs were built before
production was discontinued in 1961 See Johnson,
Reynold
Raman amplifierA mechanism based upon Raman
scattering that provides gain in optical transmissions
This type of amplification is common to C- and
L-band frequencies, but has also been suggested for use
in the S-band It is expected to increase power and
lower costs in dense wavelength division multiplexed
(DWDM) systems without the nonlinear waveform
distortion characteristic of erbium-doped
amplifica-tion mechanisms, especially in long-haul cables
Raman scatteringLow-level scattering associated
with light deflecting off obstacles in its path As a
beam of light encounters an obstacle, there is
inter-action between the incident photons and the obstacle's
molecules, resulting in a change in the direction of
some of the light and a shift in its frequency, called
Raman scattering The scattered light is proportional
to the intensity of the incident light
Depending upon context, Raman scattering may be
considered as noise or may provide useful
informa-tion about the object from which it is scattered When
Raman scattering occurs in response to
environmen-tal conditions, or is an unexpected side-effect, it is
called spontaneous Raman scattering (SpRS) When
it is deliberately induced, or is an expected
side-ef-fect, as in an amplifier or spectroscope, it is called
stimulated Raman scattering(StRS) When the
wave-length emitted by a laser light source corresponds to
the excited energetic vibrational level, it is called
resonance Raman scattering(RRS).
and the result compared with spontaneous Raman scattering for research or test purposes Raman in-struments are considered far-field inin-struments due to the distance between the detector and the scattering point of the light, and their spatial resolution is gen-erally limited to the approximately wavelength ofthe source light For higher resolutions, scanning probe microscopes may be suitable Some companies are now combining the capabilities offar-field and near-field instruments to enable more precise targeting in conjunction with higher spatial resolution
In instruments designed to detect and assess Raman scattering, an optical tip may be used as a probe and!
or an optical fiber bundle may deliver the Raman impulse to a monochromator and imaging detector Undesirable Raman scattering may occur in optical transmission links carrying more than one wave-length due to interband interactions where power is transfered from shorter to longer wavelengths and may contribute to pulse distortion Raman filters are available for some types of fiber optic probes See Raman amplifier, Raman spectroscopy, Rayleigh scattering, scanning probe microscope
Raman spectroscopeAninvestigative instrument that induces light scattering from an illumination source aimed at a target sample By assessing the scat-tered returning signal, characteristics related to the composition and density of the sample can be de-tected This technology is becoming competitive with infrared (IR) analysis due to the reduced cost of la-ser diode light sources Raman-detecting spectro-scopes are available in a variety ofwavelengths The spectroscope may include a computer interface for the transmission ofdata for more extensive analysis See Raman scattering
RAMbusrandom access memory bus See bus, ran-dom access memory
RAMDAC random access memory digital-to-analog converter A graphics adapter display circuit which converts the computer digital information for repre-senting the screen image into analog signals that a cathode-ray tube (CRT) display monitor can use Ramsden, Jesse(1735-1800)AnEnglish instrument maker and engraver who invented micrometers, a pyrometer and a new type ofeyeglasses and authored
a description of a new ''universal equatoreal." He is credited with furthering the technology of the Cas-segrain telescope devised 100 years earlier by Guillaume Cassegrain Ramsden was elected to the Royal Society in 1786 and received the Copley Medal
in 1795
RAND 1 random 2 rural area network design random access memoryRAM A type of computer memory in which data in any part of memory can be accessed in any order, that is, it is not restricted to reading and writing data sequentially as in serial data, tapes, etc RAM is a very fast access device almost universally incorporated into computing systems for use by applications for frequent operations or those that must be executed quickly
In the mid-1970s, microcomputers typically had 4
Trang 5Fiber Optics Illustrated Dictionary
Kbytes RAM and the price per kilobyte was about
$100 Since then, the amount of memory installed in
microcomputers has increased as prices have
de-creased While there have been some interim
fluctua-tions in prices, they have dropped dramatically as
installed quantities have increased, as illustrated in
this summary of the quantity/price changes over two
decades
random access storage RAS A variety of types of
memory and storage drives (e.g., hard disk drives)
that enable data to be randomly accessed rather than
sequentially accessed These tend to be faster and
more convenient than sequential access storage such
as older tape drives See random access memory
random early detection (RED) An active router
queue mechanism for detecting incipient congestion
on a network through a number of congestion
indi-cators RED drops packets probabilistically rather
than when the buffer overflows, with the probability
increasing as the queue size increases Signals from
RED may indicate persistent congestion, information
that is useful for network management
RED can help control the average size of a queue on
a system that experiences occasional transmissions
bursts and thus reduces the chance of data loss The
maximum probability ofa router packet being marked
is set with themaximum drop rate The random
na-ture of RED reduces the tendency of synchronized
processes to lock up when congestion is detected
Dropped packets have traditionally been used as a
congestion indicator, but with RED, packets may be
dropped before a queue overflows and thus may not
always be the best indicator of congestion for
secu-rity purposes RED also may not be the best
mecha-nism for effectively handling a very large number of
very tiny transmissions See explicit congestion
no-tification
random number generator A device or algorithm
intended to produce a truly random number or one
that is at least difficult to predict This is not as easy
as it might seem, especially in computing devices that
Time
Period
mid 1970s
late 1970s
early 1980s
1983-1984
1985-1986
late 1980s
early 1990s
mid 1990s
early 1998
late 1998
late 2000
late 2001
Typical
Quantity
4 Kbytes
8 Kbytes
128 Kbytes
256 Kbytes
1 Mbyte
4 to 8 Mbytes
8 Mbytes
8 to 16 Mbytes
16 to 32 Mbytes
32 to 64 Mbytes
32 to 128 Mbytes
128-256 Mbytes
Approx.
Price/Mbyte
$100,000
$2000
$1000
$700
$700
$400
$250
$200
$4
$1
$0.50
$0.10
operate on rule- and clock-based principles Their consistent modes of operation may cause them to generate the same random number, or the same pat-tern of random numbers, each time a random num-ber generator is invoked This is why most random number generators associated with computers are considered to generate pseudorandom numbers Sometimes the "randomness" of the number is at the whim of a software developer who has written or compiled a random number-generating routine Many computer operating system-level or machine-level random number generators will fetch the same num-ber the first time they are invoked and some will gen-erate the same (or nearly the same) sequence of ran-dom numbers the first time they are invoked after a machine has been restarted or reset Some random numbers are simply extracted from a list
To overcome some of the problems of generating an unpredictable or "true" random number, program-mers have tried several strategies based on looking
at a changing timer or piece ofdata unconnected with the regular operation of a system Various input op-erations on the part of the user, or processes associ-ated with another application on the system, are some-times sampled to obtain an unpredicted value Sci-entists have investigated the use of radioactive de-cay and radio waves for generating a random value
or seed There are even semiconductor-based random number generating devices based on amplifying and sampling electronic noise
In 1998, Matsumoto and Nishimura described a 623-dimensionally equidistributed uniform pseudoran-dom number generator that they called Mersenne Twister This is a fast, efficient algorithm with a longer period than other generators The source code
is available online in C and Java
DIEHARD is a suite of programs for testing random number generators developed by G Gasram, with support from the National Science Foundation Source code in C is available for several platforms With the growth of distributed networks like the In-ternet, it becomes possible to go outside the local sys-tem to find another syssys-tem or timing device from which to fetch a number to use as a random value or
a seed for generating a random number on the local system There is even a site called www.random.org that provides a random number service for Web us-ers
Random numbers are not just intellectual oddities They are used in a wide variety of practical applica-tions, including fundamental research, gaming theory and applications, gambling systems, statistical stud-ies, and software/hardware systems testing They are especially important for generating encryption keys and cryptologic algorithms for securing data and digi-tal voice communications See encryption
range 1 The extent, distance, or scope represented
or traversed 2.Ina Global Positioning System (GPS),
a fixed distance between two points, such as the dis-tance between a GPS receiver and a satellite 3 In mobile communications, the maximum distance of a transmission sufficiently clear to be useful
Trang 6out the use ofa conventional ruler Sonar is a type of
rangefinding system, as are optical or acoustic
dis-tance sensors in robotic systems Many automatic
focus cameras have builtin infrared-based
rangefinding systems in which a beam of invisible
light is aimed at the object to be photographed and
reflected back (up to a certain distance after which it
is considered to be at infinity in tenns of the lens
ca-pabilities of the camera) By calculating the time of
flight ofthe beam from the camera, to the object, and
back to the camera, the distance can be estimated
ac-curately enough to focus the lens Sometimes two
modulated sub-beams of the same order of
magni-tude following one another are used so that a
com-parison can be made for accurate rangefinding
Semiconductor lasers in invisible and visible light
ranges are incorporated into many rangefinders
In-visible rangefinders are useful as surveillance
de-vices, intelligent vehicle systems, robotics sensors,
and level meters (e.g., grain bins) Visible light
rangefinders are handy when the operator needs to
know exactly where the beam is targeted Afiber
op-tic lightguide may be used to propagate the light from
the receiving lens to a photodiode
RAP See Route Access Protocol
Rapid City IP switchSee Accelar routing switch
Rapid Transport ProtocolRTP.Anend-to-end, full
duplex, high-speed, connection-oriented transport
connection protocol Flow control is adaptive
rate-based (ARB) at the endpoints, and error recovery is
handled via selective retransmission RTP can be used
to transport Systems Network Architecture (SNA)
session traffic, for example
RAR 1 An efficient data compression program
de-veloped by Eugene Roshal as shareware for DOS/
Windows-based systems Files are just a little smaller
than those generated by PKZIP and can be made
self-extracting UnRAR utilities are also available for the
Macintosh See Java Archive, LHarc, PKZIP 2
re-turnaddress register, RA register A programming
register or data compartment (as might be found in a
stack, for example) for storing and accessing return
address information Depending upon the
architec-ture, other registers associated with the RA register
typically contain variables, parameters, etc
RARE See Reseaux Associes pour la Recherche
Europeenne
rare earthSome rare earth elements are commonly
used as doping agents which can aid in the
propaga-tion of signals when added to transmissions media,
such as optical fiber, during manufacture Rare earth
doping is also being applied toward the design and
manufacture of electrically pumped lasers that
em-ploy electronic circuitry Erbium, Gadolinium,
Eu-ropium, and Samarium are examples ofrare earth
el-ements
rare earth dopingAmeans of using small amounts
ofrare earth substances to alter the
transmission-car-rying capacity of a medium such as a fiber optic
waveguide Doping allows a signal to be amplified
by the stimulation of the rare earth substances, thus
tance that the signal can transmit Since fiber optic cable is not a long-distance carrier in the same sense
as other media, anything which increases the distance
is a great boon to fiber cable manufacture Transoce-anic cable applications can particularly benefit from this technology Erbium is one ofthe rare earths used
in this process; Samarium is another, used to dope lasers See doping
RARP See Reverse Address Resolution Protocol
RAS 1 See random access storage 2 RAS The nick-name for Sun Microsystems raster-fonnat files The file extension ras may be used to distinguish these files See raster 3 See remote access server 4 Royal Astronomy Society 5 Russian Academy ofSciences
RASC 1 See Radio Amateur Satellite Corporation
2 Royal Astronomy Society of Canada
raseracronym radio amplification by stimulated
emission of radiation
rasterA sequence of adjacent scanning lines on a cathode-ray tube (CRT) displayed quickly enough and closely enough together that they are perceived
as a fairly unifonn coverage ofthe display surface of the tube The full coverage of the screen is called a frame Most television broadcasts and computer monitor images start the raster at the top left comer, with each line sweeping horizontally left to right down the tube, and ending in the bottom right cor-ner There may be two sets of interleaved rasters dis-playing concurrently Color raster systems typically employ three beams: red, green, and blue (RGB), the primary colors oflight (the primary colors ofpigment are red, yellow, and blue) Unlike a vector display, in :~:~i~;l~~~~~;~~t:~~~:~~}:~~t~i tB
cause the image to appear jagged or staircased
Anti-aliasing can perceptually decrease this effect See antialiased, bitmap, interlaced, vector display, refresh
raster fillThe fillinginofspaces between raster lines
on a CRT to provide an image that appears brighter
or sharper See raster
raster image processor RIP Adevice to accelerate the process of data conversion, such as scan conver-sion on a monitor, or vector-to-raster converconver-sion on
a high-end printer PostScript files, which are widely used in the printing industry, define vector-fonnat files so that they can be output to a variety of types
of devices at the highest quality possible for that de-vice Thus, service bureaus will take a PostScript file (as generated by a desktop publishing product such
as PageMaker or FrameMaker) andRIPthat file to their high-quality imaging device to create a raster-based paper printout or a paper, asbestos, or metal printing plate
A printer device file is a file that includes infonna-tion specific to the capabilities ofa printer that is used
in "rasterizing" an image This can be used by a Post-Script RIP, for example, toturnthe vector-based in-structions into objects and raster points that can be output to a printer Adobe Acrobat distiller is a fonn ofRIP that converts PostScript into high-quality PDF
Trang 7Fiber Optics Illustrated Dictionary
files (popular on the Internet) These files can then
be readily viewed on a variety ofmonitors and,
ifde-sired, printed to a variety ofprinters
raster lineA single line sweep (usually horizontal)
of the electron beam on a cathode-ray tube The time
during which the image is rendered by exciting the
phosphors on the inside front of the CRT When the
beam travels back to start the next raster line, it is
sup-pressed in a process called blanking See blanking,
frame, raster
rastering, rasterizingThe process by which an
im-age is converted to data, usually as a stream of bits
Rastering is a common processindocument
trans-fer, and is often accompanied by compression and
decompression ofthe data in order to minimize
trans-mission time
RATCCradar air traffic control center
rateThe cost per object unit or unit of time of an
equipment lease or service Phone services are
typi-cally billed at a flat rate per month with individual
surcharges for connect time for long-distance calls
or cellular calls Internet Service Providers (ISPs)
typically charge a flat rate per month, although some
add surcharges for popular services like email, file
storage, and Web access
Rate Adaptive Digital Subscriber LineRADSL A
means to optimize the throughput of data
communi-cations in aDigital Subscriber Line (DSL) service by
adjusting the connection to compensate for variations
in the line characteristics of the local loop The
de-sired bit rate may be initialized manually or
automati-cally at startup or, if there is a way to monitor line
conditions, may be adjusted as needed, based upon
the performance characteristics of the line This is in
addition to the normal rate adaptation capabilities of
the ADSL service See chart under Digital Subscriber
Line See Asymmetric Digital Subscriber Line
rate averagingAneconomic method for providing
uniform, simpler pricing options for equipment or
services which normally might vary widely in their
costs ofinstallation and operation to different groups
of consumers For example, phone companies have
fairly uniform rates over a wide variety of terrains,
services, and population densities Postal services
also employ rate averaging; in other words, a letter
to the next town requires the same postage as a letter
to the most distant part of the country from the
sender's locality
rate decrease factorRDF In ATM networking, an
available bit rate (ABR) flow control service
param-eter which controls the decrease in the transmission
rate of cells when it is needed See cell rate
rate increase factorRIF In ATM networking, an
available bit rate (ABR) flow control service
param-eter which controls the increase in the transmission
rate on receiving an RM-cell See cell rate
rate periodIn telephone service, a segment of time
designated as a specific period in order to assign
bill-ing charges Rate periods are determined by
evalua-tion of phone call traffic volume, cultural customs,
and time of day, and then usually established
semi-permanently so that subscribers become familiar with
peak and off-peak rate periods Rate periods vary from country to country In the U.S., for example, the least expensive rate period on weekdays is from 23 :00
to 08:00, and cheaper rate periods are available on weekends Companies often schedule fax transmis-sions to be sent out automatically after midnight to take advantage of the cheaper rate period See rate period specific
rate period specific When telephone calls which cross rate periods are billed at a higher or lower rate when the period changes, they are calledrate period specific International calls originating in the U.S are
usually not rate period specific, and the call is billed according to the rate period during which it was ini-tiated See rate period
Rate Quote SystemA computerized telephone rate/ quote system which can be accessed by TSPS opera-tors
rated voltageA designation of the voltage at which
an electrical component is set to operate, or, if put in
a variable voltage environment, the safest maximum voltage at which it can be used for extended periods without risk of hazard or component burnout RATPSee Reliable Asynchronous Transfer Protocol rat's nestMess; poor configuration; snarled, com-plicated arrangement of wires, machines, processes,
or code statements
RATSRadio Amateur Telecommunications Society RATS broadcasts to a Java-enabled site on the Inter-net on a 145.790 MHz channel
RaWread after write
RAX See rural automatic exchange
RAYSee Rayshade
RAYDACRaytheon Digital Automatic Computer A historic large-scale computer manufactured by Raytheon and named in the same tradition as the ENIAC The RAYDAC began operations in 1953 See ENIAC, JOHNNIAC, UNIVAC
Rayleigh discAn instrument for the fundamental measurement ofparticle velocity by means ofacous-tical radiometry
Rayleigh expansionIn the context ofdiffraction grat-ings' the consideration of electromagnetic variables
in addition to what was known about the diffraction
of light in the early 1900s This improved our under-standing of diffraction patterns within gratings and helped reveal the importance ofwavelength interac-tions with grating surfaces
Rayleigh's word came about as a result of observa-tions about diffraction made by Wood a few years earlier that were anomalous in the context of exist-ing theories about the diffraction oflight from a grat-ing surface Rayleigh suggested that the diffraction pattern ofthe incident light as it propagated from the grating could be expressed as a mathematical series both within the region of modulation of the grating and outside the modulated region This theory is still used to describe the outer region but has been found insufficient in some circumstances (e.g., resonance gratings) for explaining light propagation and reflec-tion in the inner corrugareflec-tions ofthe grating See grat-ing, Talbot effect, Wood-Rayleigh anomaly
Trang 8as a result of interaction with the various objects or
particles which are part of the environment of the
transmission This phenomenon is often found in
mobile communications in which the interaction of
the radio signals with the surrounding terrain causes
signal fading A number of techniques are being
de-veloped to reduce the incidence of fading For
ex-ample, in systems where long delays are acceptable,
fade can be reduced by interleaving Named after 1.W
Strutt (Lord Rayleigh)
Rayleigh scattering Scattering of radiant energy by
contact or interaction with minute suspended particles
such as dust or moisture Rayleigh scattering may
result from fluctuations or impurities within a
trans-mission medium that create small amounts
ofrefrac-tion compared to the transmission wavelength (This
refraction is typically not desired, though impurities
are sometimes introduced to modify the transmission
properties ofa medium.) The phenomenon is named
after1.W Strutt (Lord Rayleigh)
In fiber optics, fluctuations in the composition and
density of the glass or plastic waveguide may cause
Rayleigh scattering See attenuation, doping, Raman
scattering
Rayleigh, Lord (1842-1919) John William Strutt, an
English physicist and mathematician who made
fun-damental mathematical contributions to the field of
physics, including atomic physics, acoustics, and
optics In1870, he published On the Light from the
Sky - Its Polarization and Colour, which presented
his ideas and calculations based on observations of
the scattering oflight and the relationship ofthe
scat-tered radiation to wavelengths In 1904 he was
awarded a Nobel Prize for his discovery of argon In
1907 he investigated anomalies and characteristics of
resonance phenomena in the context of diffraction
gratings Rayleigh scattering is named after him See
Wood-Rayleigh anomaly
RAYNET See Radio Amateur Emergency Network
Rayshade Anative scene description language used
with the Rayshade 3D raytracing software for
mod-eling light effects on 3D rendered surfaces/objects
Rayshade files may be distinguished by a ray file
extension
RB 1 See radar beacon 2 reverse battery
RBBS remote bulletin board system See bulletin
board system
RBOC See Regional Bell Operating Company
RBS See robbed-bit signaling
RC6 Ablock cipher encryption algorithm developed
by RSA Security Inc that was selected as a finalist
when entered as a submission to the U.S Federal
Advanced Encryption Standard RC6 was jointly
de-veloped by Ron Rivest (originator of the MD series
message delivery algorithms), Matt Robshaw, Ray
Signey, and Yiqun Lisa Yin ofRSALaboratories and
was originally specified in1998 It is the
evolution-ary descendent of the RC5 block cipher, which is
based upon the concept of data-dependent rotations
See Rijndael
RCA 1 remote control access 2 See Radio
Corpo-RCA connectors A basic electrical connection for-mat for cables carrying audio/visual and sometimes data signals The RCA connector is a simple, peg-shaped jack or plug commonly used for single-sig-nal cables (though they are sometimes also attached
to the end ofcoaxial cables, with only one of the two coaxial conductors actively transmitting through the RCA end) RCA connectors are widely used in the audio and video broadcast and recording industries
to interconnect components such as audio compo-nents, VCRs, DVD players, camcorders, switchers, and more RCA connectors depend upon friction to stay in place, which means they are easy to plug and unplug, but should not be used for connections where
a secure connection is vital or where there is tension against the connection (BNC connectors work better
in these circumstances)
RCA Cables& Adapters
RCA-jackcables are.frequently combined in one cable for convenience (the signals ron on separate wires), with the jacks color-coded (yellow-video, red-audio mono/combined or audio right, white-audio left) to help consumers interconnect the correct plugs Three common examples include A video, audio-mono B audio left, audio rightC.audio left, video, audio right.
There are many adapters available to enable RCA cables and components to connect with other compo-nents (headphones, portable recorders, etc.) Some common adapters include A gender bender or ex-tender for adding an extra length ofcable B RCA to mini (ca 1116-in.) audio monoC.RCA to ca lI8-in audio stereo D RCA to ca lI8-in audio mono E RCA
to audio mono female F RCA splitter/joiner to split a single signal out to two receivers or to join two sig-nals into one.
RCC1 See Radio Common Carrier 2 reduced com-plexity computing 3 remote control center/circuit RCF 1.See Radio Control Function 2 See Remote Call Forwarding 3 remote control facility
Trang 9Fiber Optics Illustrated Dictionary
RCLruntime control library
RCMremote carrier module
RCPremote control panel
RCS 1 radar cross-section 2 See remote control
system 3 See revision control system
RCVSee remote concentration unit
RD See routing domain
RDB1 receive data buffer 2 remote database
RDF 1 radio direction finding In radar, a British
term for a tracking system based upon locating the
source ofunidentified or foreign radio signals 2 See
rate decrease factor
rdistremote file distribution program A program to
distribute and maintain file copies on multiple hosts
on a network See DHCP
RDP1 radar data processing 2 rapid development
program 3 See Reliable Data Protocol
RDT 1.recall dial tone 2 remote digital terminal
RE radio emergency
REACReeves Electronic Analogue Computer
Ahis-toric large-scale analog computer series first
intro-duced in 1948 by the Reeves Instrument Corporation
One of the selling points of REAC computers was
the "patchbay system" for patching interconnections
The Aeronautical Computer Laboratory (ACL) was
among the first organizations to purchase REAC
computers Documents about this system form part
ofthe MarvinL.Stein Papers collection at the Charles
Babbage Institute and are also included in the
Na-tional Museum of American History Oral History
Collection
readA command commonly used in software
appli-cation menus to provide the user with the ability to
load data from permanent or semipermanent storage
such as a floppy diskette, hard drive, cartridge drive,
tape, RAM disk, or other medium Files on a drive
can be set with protections to be read only, or read!
write, or write only so that they can't be read
Simi-larly a disk can usually be set to write-enabled or
write-protected mode Most optical storage media are
read only, and cannot be rewritten or written without
special, more expensive devices than are used by
most consumers
read only memoryROM A nonvolatile,
random-access data storage unit which is preconfigurable, and
not changeable by the user by normal means ROM
chips are commonly used for kernel level operating
instructions or other information for the low-level
functioning of a system which needs to be quickly
accessed and transparent to the user See CPU, RAM,
PROM, EPROM, kernel
read-while-writeRWW A capability of some data
storage devices to verify written data in realtime This
can be accomplished by executing code in one array
while data are stored in another In March 2000,
Toshiba Corporation announced that they had
devel-oped the first 64-Mbyte read-while-write NOR flash
memory device for use in various types of wireless,
handheld consumer devices, and set-top boxes See
linear tape open
Realtime Transport Protocol RTP A
packet-ori-ented data delivery services protocol for end-to-end
services to support applications transmitting realtime data such as Interactive audio/video applications over unicast and multicast networks RTP provides time stamping, rate control and source/payload identifica-tion as augmented by the Realtime Transport Con-trol Protocol (RTCP) to enable the monitoring of data delivery in a scalable manner RTP and RTCP are in-dependent of the underlying network and transport layers and may be integrated into the processing of
an application rather than implemented as a separate layer RTP was submitted as a Standards Track RFC bySchulzrinneetal in January 1996 SeeRFC 1889
Real Time Markup Language RTML A trade-marked, proprietary set of extensions to the Hyper-text Markup Language (HTML) for specifying the inclusion of streaming textual data on HTML-based Web pages using RTTP data as a source Thus, live, streaming text data can be readily incorporated into
a Web page This is of interest to vendors of realtime services and information such as stock quotes, news,
or racing results
RTML is a product of Caplin Systems Ltd based on Dynamic HTML (DHTML) combined with Java 1.1
or higher Once it is installed, the user need not worry about programming any Java or other language All that is required, once the streaming engine is installed,
istoadd a <SCRIPT> tag with optional attributes to the HTML pages Newer browsers are required to view the streaming text messages The software will alert the user if the browser is not compatible with the RTML feed
Real Time Streaming ProtocolRTSP An extensible, application-level protocol for delivery control ofreal-time data RTSP enables the on-demand delivery of multimedia streams delivered, for example, by ser-vice delivery protocols such as Rapid Transit Proto-col Sources ofdata may include stored or live stream-ing data feeds The protocol supports multiple data delivery sessions RTSP was submitted as a Standards Track RFC by Schulzrimle et al in April 1998 See Rapid Transit Protocol See RFC 2326
real worldA phrase to describe the application or testing of products or services in a real world envi-romnent, in other words, in the end population or fa-cility for which the product or service is intended Thus, a real world test of a new telephone might be
to install it in a telemarketing firm A real world test
of a new computer might be to put it into a classroom
or business Real world testing is sadly lacking in the software industry The pressure to get products to market tends to cause software companiestorelease
a product after it has been tested in-house and through beta testers, but not by actual customers This can have disastrous consequences as real world custom-ers will always use the product in ways that cannot
be anticipated by programmers and beta testers
RealAudioAcommercial on-demand, multiplatform, realtime audio player for multimedia-capable com-puters from Progressive Networks The RealAudio format is widely supported on the Web and may be played through a Web browser plugin or launched separately (on multitasking systems) Earlier versions
Trang 10phonic sound designed for the 14.4 and 28.8 kbps
transmission speeds typical of dialup network
con-nections at the time Subsequent versions are being
updated to support higher-bandwidth connections as
well RealAudio files typically use the ra file
exten-sion
realtimeThe term realtime is used somewhat
differ-ently by two groups ofpeople: (1) marketing
person-nel and users and (2) technical systems designers and
operators First, a more general description of
real-time
Realtime is a description of computer processes that
occur at a speed which corresponds with human
per-ception of the speed of events in "real life," and in
immediate response to requests.Inother words, a ray
tracing program that takes two hours to render and
display a frame of an animation is not realtime, as
there is a delay during which the viewer must wait
for the image to be constructed and displayed.In
con-trast, a fast action video game, in which the motions
are displayed at 20 or 30 frames per second so that
they are perceived as natural motion, and in which
the joystick, mouse, or other inputs from the user have
immediate effect upon the game, is considered to be
a realtime game Realtime flight simulators are used
to train pilots, and realtime rendering programs exist
on some fast, high-end platforms
Intelephony, realtime processing involves handling
calls as they are received If callers are put on hold
or experience delays in automated menu processing
systems, the system is not providing realtime service
Realtime effects and processing, especially if they
involve graphics, typically require fast, wide data
buses, fast CPUs, and efficient mathematical
algo-rithms for handling input, calculations, and display
Inspite ofthe resources needed, humans seem to have
a compelling interest in creating realtime scenarios
and striving for real and fantasy simulations that
mimic or outstrip the pace of life This creates
eco-nomic incentives for creating realtime simulations,
especially in the entertainment industry, with
audi-ences eager for these scenarios Indeed, many of the
advances in computer technology have been
pio-neered, fueled, and financed by the games industry
In a more technical systems implementation sense,
realtime occurs in a computing system when
com-putations are processed not only as expected, andwith
logical correctness, but also within certain
predeter-mined or expected timing frames, and with a certain
guaranteed minimum level of usefulness of the
ser-vice.Inthis sense of the word, speed is not so much
the issue, as is the appropriateness of the response
time to the task at hand Some realtime systems rely
on sensor and other feedback mechanisms, and may
be used not only in consumer computing operations,
but also in industrial robotics or remote sensing
ap-plications Realtime functionality is likely to be
im-portant in future space probes and the vehicles that
deploy them, as well as in intelligent vehicle
auto-navigation systems
realtime capacityThe capability of a system to
are received.Inconfiguring and tuning various types
of networks, realtime capacity is one of the criteria many systems use as areference point for smooth op-erations
realtime diagnosticsTests which allow measuring, diagnostic, or display instruments to monitor and re-port events as they are occurring Most electrical in-struments work in realtime, reporting circuit status
at the moment the instrument is applied to the circuit
This is not so easily done with sophisticated computer systems, where it is difficult to track everything hap-pening on the system at anyone time More often software "monitors" (statistical display programs) for specific processes are used, which include the repre-sentation of statistics for load, CPU speed and pro-cesses, congestion, failed packet ratios, quality ofser-vice (QoS), etc
Realtime Transport ProtocolRTP An IETF data format that provides higher video priorities to facili-tate realtime multimedia transport overInt~met Pro-tocol (IP)
reassemblyAnimportant aspect ofnetwork commu-nications in which an Internet Protocol (IP) datagram
or other type of data unit, which has been split up at the source or en route and may have been transmit-ted in sections at different times and/or through dif-ferent routes, is reassembled at the receiving end The process ofdisassembly and reassembly allows pack-ets to be transported through a large, dynamic net-work environment, like the Internet, which changes topologically in unpredictable ways Reassembly and synchronization are also important in applications like videoconferencing, where more than one line may be used to transmit the various audio and video signals that make up the communication
rebootTo cause a system to return to its initial oper-ating status, as it was at the beginning of a system startup, usually without turning off the power This typically clears memory, closes all applications and files, sets initial test sequences and starting param-eters for timing, sound, video, etc and reinitializes devices The term is derived from "boot," which comes from "bootstrapping."
If the power is turned off to reboot a system, it is called acoldboot You should always count to 20 before flipping the power switch on again Electronic components are sensitive to sudden power surges, and there is always some residual power in some of the chips that needs to drain offwhen electronics devices are turned off
Most reboots are warm boots, in which the power to
the system is not interrupted Rebooting is seldom necessary in stable operating systems, which can op-erate 24 hours per day for years without crashing, hanging, or fragmenting memory However, some op-erating systems do not handle error conditions or memory management well and may hang, freeze, or crash, in which case a reboot may be necessary in order to continue using the system
receive-only deviceAdevice which can receive data but not send it Technically, there are very few
receive-· : : ; : 1 1 ' receive-·
I '