Fiber Optics Illustrated Dictionary - Part 81 docx

Fiber Optics Illustrated Dictionary Radio Communication Laws ofthe United States The sinking of the Republic and the Titanic, in addition to the International RadioTelegraphic Conven- tion, were strong factors in the development of Ameri- can regulations for radio communications. In 1910 and 1912, U. S. acts were approved resulting in the publication of the Radio Communication Laws of the 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 carrying 50 or more persons to be " equipped with an efficient apparatus for radio communication capable of transmitting and receiving 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 messages over a distance of at 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 of two or more persons skilled in the use of such apparatus, one or the other of whom 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 communications. See International Radiotelegraphic Con- vention. Radio Control Function RCF. In a PACA-E Per- sonal Communications System (PCS), the point towards which Radio Terminal Function transmissions are directed and from which the RTF interacts with other network entities in the processing ofa PACA- E (priority access) call. See Priority Access and Chan- nel Assignment. Radio Corporation ofAmerica RCA. An offshoot of General Electric founded in 1919 as a result ofa 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 of radio receiving sets and crystal detectors. In 1921, David Sarnoff joined the company as its general manager, and later moved up in the corporation, becoming vice president in 1926. Sarnoff was a colorful part of its history 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. 792 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, aposition 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 television broadcasting, and for various types of wireless communication. The frequency range has been administratively subdivided into a number of catego- 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 transmitted at the speed of light, they enthusiastically sought ways to achieve practical embodiments of the possi- bilities. The gradual discovery and harnessing of electromagnetic frequencies to carry meaningful communications 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 of natural 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 radio 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 history of modem radio technology starts with Lee de Forest's invention of the Audion, a three-element electron tube derived from Fleming's two-element tube. The addition of the third element was highly important, as it enabled the flow of electrons to be con- trolled which, in tum, made it possible to build radio signal amplifiers for hundreds of different applications. 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 technologies, but most people are unaware that he broadcast music from the town of Lyngby, on March 4, 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 ofpractical methods of radio broadcasting, creative minds quickly grasped the so- cial, cultural, military, and commercial applications of radio 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 © 2003 by CRC Press LLC replaced hobbyist crystal radios. Guglielmo Marconi was a young, ambitious inventor 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. A true broadcasting pioneer, Doc Herrold began transmitting 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 broadcasting 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 KDKA in 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, however, 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 electron tube-based radio set, around 1925. Hoover and Coolidge were two of the first presidents to exploit the informational andpoliticalpotential of radio communications. [Library o/Congress American Memory National Photo Company Collection.] Calvin Coolidge was quick to exploit radio technology in the U.S. in the 1920s, for political communications, as was Vladimir Lenin in Russia. Radio is now an inextricable aspect of political campaigns and communications and is used by government agencies for coordination, national security, and emergency services. The general public benefited from wireless letters and 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 ofa 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 processing speeds and reducing component sizes even further. Radio is still a highly significant communications 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 Protocol RLP, RLP 1. A protocol standardized by the Telecommunications Indu~try Asso- ciation (TIA), in the mid-1990s, using SDI, afonnal specification language. RLP is a data link layer circuit-mode protocol for connecting a Mobile Tenni- nal (MT) with a Mobile Base Station (MBS) to provide a stationary digital radio interface through a public switched telephone network (PSTN) to another data-compatible telephony device. This makes it useful for cellular data transmissions applications. Radio Technical Commission of Aeronautics RTCA, Inc. Aprivate, not-for-profit corporation pro- moting consensus-based recommendations for communications, air traffic management, navigation, and surveillance issues. The RTCA was established in 1935. It now represents more than 270 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 Function RTF. In a 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 wave An electromagnetic 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 properties; 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 793 'F., ;;t: •. ';.>.~.~.': :. . ,', ~, © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary frequencies have shorter wavelengths) have been designated 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. An international nonprofit professional or- ganization of network and local news executives in the broadcasting, cable, and multimedia industries. Established in 1946, the RTNDA promotes high standards 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. radiogram 1. A telegram sent through radiotelegraphy, also called "radiograph." See telegram. 2. Com- bined radio receiver and phonograph. radiometer A device for measuring the intensity of electromagnetic radiation, which may include visible, UV, or infrared light and emanations beyond the optical spectrum. A photometer 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 intensity. F or scientific understanding and high precision applications, various research scientists and standards bodies have sought to derive absolute or reference measures for luminous intensity, luminous flux, and illuminance. A goniophotometric detector calibrated against the realized luminous intensity standard can be used to establish a unit of luminous flux. A similar instrument with a charge couple detector (CCD) may be used with standard intensity lamps to detenninance luminance. See photometer. radiometeorograph See radiosonde. radiophone A device that transmits sound through radio waves. Although the tenn is less common, radiophones are everywhere; they have more individual names now due to their specialization (cordless phones, cell phones, etc.). radiosonde, radiometeorographA miniature, automatic radio transmitter usually sent aloft on an air- craft or meteorological balloon, to transmit back meteorological information, such as temperature, humidity, pressure, etc. radiotelegraphy Transmission of telegraph signals through radio waves. The carrier wave was modulated to carry Morse code. The two main types were continuous-wave (CW), in which the carrier wave was 794 interrupted to fonn the coded symbols, and interrupted continuous-wave (ICW), in which the carrier was modulated at a fixed frequency. radiotelephony The art and science of communicat- ing through radio waves, often by means of various types of radiophones. RADIR random access document indexing and re- trieval. RADIUS Protocol Remote Authentication Dial In User Service. A client/server network protocol for carrying authentication, authorization, and configuration information between a Network Access Server (NAS) (a client), desiring to authenticate its links, and a shared authentication server. RADIUS was submitted as a Standards Track RFC by Rigney et al. in June 2000. A RADIUS client passes user information to designated RADIUS servers and acts upon the responses. The server receives connection requests and authen- ticates the user, returning all configuration information 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 An administrative client/server protocol used in conjunction with RA- D IUS 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 accounting request associated with a database of users ofa 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 accounting 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. RADL radio laboratory. 2. See Reticular Agent Defi- nition Language. radome A 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. RADSL See 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. © 2003 by CRC Press LLC RAIS redundant array of inexpensive systems. raised floor distributionA type of structure 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 disk An area 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 if the system is turned off. A RAM disk is a means of disk 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. RAM Mobile DataAn open 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 messages to users or to other stations. RAMAC Random Access Memory Accounting Ma- chine. A historic large-scale computing machine announced by ffiM, in 1956, for plant automation accounting and data processing applications. It included magnetic disk memory with a capacity of5 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 amplifier A 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 amplification mechanisms, especially in long-haul cables. Raman scattering Low-level scattering associated with light deflecting off obstacles in its path. As a beam of light encounters an obstacle, there is interaction 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 information 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-effect, as in an amplifier or spectroscope, it is called stimulated Raman scattering (StRS). When the wavelength emitted by a laser light source corresponds to the excited energetic vibrational level, it is called resonance Raman scattering (RRS). Sometimes Raman scattering is deliberately induced and the result compared with spontaneous Raman scattering for research or test purposes. Raman instruments are considered far-field instruments 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 of the source light. For higher resolutions, scanning probe microscopes may be suitable. Some companies are now combining the capabilities of far-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 wavelength 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 spectroscope An investigative instrument that induces light scattering from an illumination source aimed at a target sample. By assessing the scattered returning signal, characteristics related to the composition and density of the sample can be detected. This technology is becoming competitive with infrared (IR) analysis due to the reduced cost of laser diode light sources. Raman-detecting spectro- scopes are available in avariety of wavelengths. The spectroscope may include a computer interface for the transmission of data for more extensive analysis. See Raman scattering. RAMbus random access memory bus. See bus, random 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) An English instrument maker and engraver who invented micrometers, a pyrometer and a new type of eyeglasses and authored a description ofa 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 memory RAM. 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 4 795 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary Kbytes RAM and the price per kilobyte was about $100. Since then, the amount ofmemory installed in microcomputers has increased as prices have de- creased. While there have been some interim fluctuations 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. Avariety 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 ofcongestion 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 ofa queue on a system that experiences occasional transmissions bursts and thus reduces the chance of data loss. The maximum probability of arouter packet being marked is set with the maximum 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 ofcongestion for security purposes. RED also may not be the best mechanism 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 pattern ofrandom numbers, each time a random number 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 number the first time they are invoked and some will generate the same (or nearly the same) sequence of random 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, programmers have tried several strategies based on looking at achanging timer or piece of data unconnected with the regular operation of a system. Various input operations on the part ofthe user, or processes associated with another application on the system, are sometimes 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 pseudorandom 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 system to find another system 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 users. Random numbers are not just intellectual oddities. They are used in a wide variety ofpractical applications, 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 digital voice communications. See encryption. range 1. The extent, distance, or scope represented or traversed. 2. In a Global Positioning System (GPS), a fixed distance between two points, such as the distance between a GPS receiver and a satellite. 3. In mobile communications, the maximum distance ofa transmission sufficiently clear to be useful. 796 © 2003 by CRC Press LLC rangefinderA device for detennining distance without the use ofa conventional ruler. Sonar is a type of rangefinding system, as are optical or acoustic distance 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 capabilities of the camera). By calculating the time of flight of the 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 devices, intelligent vehicle systems, robotics sensors, and level meters (e.g., grain bins). Visible light range finders are handy when the operator needs to know exactly where the beam is targeted. A fiber optic lightguide may be used to propagate the light from the receiving lens to a photodiode. RAP See Route Access Protocol. Rapid City IP switch See Accelar routing switch. Rapid TransportProtocol RTP. An end-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 developed 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. return address 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 architecture, other registers associated with the RA register typically contain variables, parameters, etc. RARE See Reseaux Associes pour la Recherche Europeenne. rare earth Some rare earth elements are commonly used as doping agents which can aid in the propagation 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 employ electronic circuitry. Erbium, Gadolinium, Eu- ropium, and Samarium are examples of rare earth elements. rare earth doping A means of using small amounts of rare earth substances to alter the transmission-carrying 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 increasing the transmissions capability and the distance 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 of the 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 of Sciences. RASC 1. See Radio Amateur Satellite Corporation. 2. Royal Astronomy Society of Canada. raser acronym radio amplification by stimulated emission of radiation. raster A 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 of the 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 of light (the primary colors of pigment 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. rasterfill The filling in of spaces between raster lines on a CRT to provide an image that appears brighter or sharper. See raster. raster image processor RIP. A device to accelerate the process of data conversion, such as scan conversion on a monitor, or vector-to-raster conversion 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 device. Thus, service bureaus will take a PostScript file (as generated by a desktop publishing product such as PageMaker or FrameMaker) and RIP that file to their high-quality imaging device to create a raster- based paper printout or a paper, asbestos, or metal printing plate. Aprinter device file is a file that includes infonna- tion specific to the capabilities ofaprinter that is used in "rasterizing" an image. This can be used by a Post- Script RIP, for example, to turn the vector-based instructions into objects and raster points that can be output to a printer. Adobe Acrobat distiller is a fonn of RIP that converts PostScript into high-quality PDF 797 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary files (popular on the Internet). These files can then be readily viewed on a variety of monitors and, if desired, printed to a variety of printers. raster line A 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, rasterizing The process by which an image is converted to data, usually as a stream of bits. Rastering is a common process in document transfer, and is often accompanied by compression and decompression of the data in order to minimize transmission time. RATCC radar air traffic control center. rate The cost per object unit or unit of time of an equipment lease or service. Phone services are typically 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. RateAdaptive Digital SubscriberLine RADSL. A means to optimize the throughput of data communications in a Digital Subscriber Line (DSL) service by adjusting the connection to compensate for variations in the line characteristics of the local loop. The desired bit rate may be initialized manually or automatically 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 averaging An economic method for providing uniform, simpler pricing options for equipment or services which normally might vary widely in their costs of installation 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 factor RDF. 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 factor RIF. 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 period In 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 798 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 transmissions 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 called rate 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 operators. rated voltage A 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. RATP See Reliable Asynchronous Transfer Protocol. rat's nest Mess; poor configuration; snarled, com- plicated arrangement of wires, machines, processes, or code statements. RATS Radio Amateur Telecommunications Society. RATS broadcasts to a Java-enabled site on the Inter- net on a 145.790 MHz channel. RaW read after write. RAX See rural automatic exchange. RAY See Rayshade. RAYDAC Raytheon 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 disc An instrument for the fundamental measurement of particle velocity by means of acous- tical radiometry. Rayleigh expansion In the context of diffraction gratings' the consideration of electromagnetic variables in addition to what was known about the diffraction of light in the early 1900s. This improved our understanding of diffraction patterns within gratings and helped reveal the importance of wavelength interactions with grating surfaces. Rayleigh's word came about as a result of observations about diffraction made by Wood a few years earlier that were anomalous in the context of exist- ing theories about the diffraction of light from a grating surface. Rayleigh suggested that the diffraction pattern of the 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 corrugations of the grating. See grating, Talbot effect, Wood-Rayleigh anomaly. © 2003 by CRC Press LLC Rayleigh fading Fading, or loss of signal strength, as a result ofinteraction 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. Anumber of techniques are being developed to reduce the incidence of fading. For example, 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 transmission 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 after 1. 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 fundamental mathematical contributions to the field of physics, including atomic physics, acoustics, and optics. In 1870, 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 of the scattered 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 A native 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. RC6Ablock 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 developed by Ron Rivest (originator of the MD series message delivery algorithms), Matt Robshaw, Ray Signey, and Yiqun Lisa Yin ofRSALaboratories and was originally specified in 1998. 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- ration of America. 3. root cause analysis. RCA connectors A basic electrical connection format for cables carrying audio/visual and sometimes data signals. The RCA connector is a simple, peg- shaped jack or plug commonly used for single-signal cables (though they are sometimes also attached to the end of coaxial 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 components, 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-jack cables 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 correctplugs. Three common examples include A. video, audio-mono B. audio left, audio right C. audio left, video, audio right. There are many adapters available to enable RCA cables and components to connect with other components (headphones, portable recorders, etc.). Some common adapters include A. gender bender or ex- tenderfor adding an extra length of cable B. RCA to mini (ca. 1116-in.) audio mono C. 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 signals into one. RCC 1. 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. 799 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary RCL runtime control library. RCM remote carrier module. RCP remote control panel. RCS 1. radar cross-section. 2. See remote control system. 3. See revision control system. RCV See remote concentration unit. RD See routing domain. RDB 1. 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. rdist remote file distribution program. A program to distribute and maintain file copies on multiple hosts on a network. See DHCP. RDP 1. radar data processing. 2. rapid development program. 3. See Reliable Data Protocol. RDT 1. recall dial tone. 2. remote digital terminal. RE radio emergency. REAC Reeves Electronic Analogue Computer. A historic large-scale analog computer series first introduced 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 of the Marvin L. Stein Papers collection at the Charles Babbage Institute and are also included in the Na- tional Museum ofAmerican History Oral History Collection. read A command commonly used in software application 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 memory ROM. 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-write RWW. 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 developed the first 64-Mbyte read-while-write NOR flash memory device for use in various types ofwireless, handheld consumer devices, and set-top boxes. See linear tape open. Realtime Transport Protocol RTP. A packet-oriented data delivery services protocol for end-to-end 800 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 independent 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 ofstreaming 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 ofinterest to vendors ofrealtime services and information such as stock quotes, news, or racing results. RTML is aproduct 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, is to add 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 Protocol RTSP. An extensible, application-level protocol for delivery control ofrealtime data. RTSP enables the on-demand delivery of multimedia streams delivered, for example, by service delivery protocols such as Rapid Transit Proto- col. Sources of data may include stored or live streaming 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 world A phrase to describe the application or testing ofproducts or services in a real world envi- romnent, in other words, in the end population or facility 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 ofa new computer might be to put it into aclassroom or business. Real world testing is sadly lacking in the software industry. The pressure to get products to market tends to cause software companies to release 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 customers will always use the product in ways that cannot be anticipated by programmers and beta testers. RealAudio A commercial on-demand, multiplatform, realtime audio player for multimedia-capable computers 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 © 2003 by CRC Press LLC of the software (e.g., version 2.0) supported mono- phonic sound designed for the 14.4 and 28.8 kbps transmission speeds typical of dialup network connections at the time. Subsequent versions are being updated to support higher-bandwidth connections as well. RealAudio files typically use the .ra file extension. realtime The term realtime is used somewhat differ- ently by two groups of people: (1) marketing person- nel and users and (2) technical systems designers and operators. First, a more general description of realtime. 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. In other 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. In telephony, 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 CPU s, and efficient mathematical algorithms for handling input, calculations, and display. In spite of the 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 economic 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 pioneered, fueled, and financed by the games industry. In a more technical systems implementation sense, realtime occurs in a computing system when computations are processed not only as expected, and with logical correctness, but also within certain predeter- mined or expected timing frames, and with a certain guaranteed minimum level of usefulness of the service. In this 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 applications. Realtime functionality is likely to be important in future space probes and the vehicles that deploy them, as well as in intelligent vehicle auto- navigation systems. realtime capacity The capability of a system to handle calls, inputs, requests, or other stimuli as they are received. In configuring and tuning various types of networks, realtime capacity is one of the criteria many systems use as a reference point for smooth operations. realtime diagnostics Tests which allow measuring, diagnostic, or display instruments to monitor and re- port events as they are occurring. Most electrical instruments 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 ofstatistics for load, CPU speed and processes, congestion, failed packet ratios, quality of service (QoS), etc. Realtime Transport Protocol RTP. An IETF data format that provides higher video priorities to facili- tate realtime multimedia transport over Int~met Pro- tocol (IP). reassemblyAn important aspect of network communications 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 transmitted in sections at different times and/or through different routes, is reassembled at the receiving end. The process of disassembly and reassembly allows packets to be transported through a large, dynamic network 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. reboot To cause a system to return to its initial operating 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 parameters 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 a cold boot. 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 off when 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 operate 24 hours per day for years without crashing, hanging, or fragmenting memory. However, some operating 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 deviceA device which can receive data but not send it. Technically, there are very few receive- 801 ·::;:11'· I ' © 2003 by CRC Press LLC . Fiber Optics Illustrated Dictionary Radio Communication Laws ofthe United States The sinking of the Republic and the Titanic, in addition to the International RadioTelegraphic Conven- tion, were strong factors in the development of Ameri- can regulations for radio communications. In 1910 and 1912, U. S. acts were approved resulting in the publication of the Radio Communication Laws of the 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 carrying 50 or more persons to be " . " 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 communications. See International Radiotelegraphic Con- vention. Radio. fonn of RIP that converts PostScript into high-quality PDF 797 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary files (popular on the Internet). These files can then be readily viewed on a variety of monitors and, if desired, printed to a variety of printers. raster

Định dạng
Số trang	10
Dung lượng	887,53 KB