Fiber Optics Illustrated Dictionary - Part 82 ppsx

Fiber Optics Illustrated Dictionary only devices in computer networking, since most devices employ handshaking to negotiate a transmission. For example, a computer printer may seem to be a receive-only device, but a printer has to be able to tell the computer when it is ready to receive, when it is busy printing and can't receive more data, and when it is available again for other jobs or other users on a network. This involves two-way communication. It may even signal the sender about its capabilities and configuration parameters. Most receive- only devices are passive devices or broadcasting devices such as simple PA speakers, buzzers, lights, etc. receiver 1. A device for receiving signals, impulses, or data transmissions. 2. A device which captures, and sometimes converts electromagnetic waves or signals into a form meaningful to humans. Receivers are often combined with tuners to specify the frequency desired, and amplifiers to increase the power of the signal. See telephone receiver. Recognized Private Operating Agency RPOA. An ITU -T designation for telephone companies providing internetworking services. Recommended Standard 232 See RS-232 for an entry and accompanying chart of Recommended Standards. RECON reconnaissance. reconnaissanceA preliminary or exploratory survey to gain information or data that can potentially be analyzed to yield information (it's often difficult to know in advance what data might later be useful or significant). Reconnaissance and surveillance are closely related activities. Reconnaissance is distin- guished from surveillance in that sUIVeillance is keep- ing watch over or observing someone, something, or some activities or phenomena. Reconnaissance is often used to support surveillance activities. Surveil- lance may also be used to obtain some of the data col- lected in reconnaissance activities. Typing a few exploratory passwords into a computer system is a reconnaissance activity intended to see if it would be easy to breach a secure computer system. Using a computer to remotely view a scene captured by a video camera is an example of a surveillance activity that may also be part ofa larger reconnaissance operation. RecordingIndustryAssociation ofAmerica RIAA. A national trade organization representing the recording industry. The organization supports and promotes the protection of intellectual property rights and business prosperity of its members who collectively pro- duce the vast majority of commercial sound recordings in the trade. The RIAA became prominent in the media when it opposed the alleged distribution of its members' copyright materials by unauthorized users through the Napster Web site. In October 2000, the RIAA announced that it was going to develop a globally standardized system for identifying digital sound files in order for the copyright owner of the files to be able to track their use and to collect any royalties rightfully due for the materials. This was intended to enable the distribution of digital editions of the recordings quickly and easily 802 over the Internet without jeopardizing the economic viability of the people creating and vending the music. http://www.riaa.com/ rectification 1. A condition in which current flowing through a material or circuit in one direction encounters greater resistance than current flowing through in the opposite direction. 2. The one-direc- tional processing of an alternating current (AC). rectifier 1. A material or circuit that offers greater resistance to an electrical current flowing in one direction than in its opposite direction. 2. A device for converting alternating current (AC) to direct current (DC). Rectifiers are commonly used on power trans- formers for electronics devices with power requirements different from the power coming directly from an electrical source. Vacuum tubes were used as rectifiers in early radios, with selenium rectifiers begin- ning to supersede them in the mid-1940s. See coherer, crystal detector, piezoelectric. recursion 1. Returning, moving back upon. 2. A repetitive succession of elements or operations that af- fects the preceding elements or operations in a like (although not necessarily identical) manner accord- ing to a finite rule or formula. Recursive algorithms often generate data or images with the characteristic of"self similarity," with fractal display programs being a popular, visually appealing example. 3. See recursion. red alarm In telephone transmissions systems, a criti- cal failure alert signal which occurs if an incoming signal is lost or corrupted. This is implemented in various T3, Tl, or SONET network systems. Red Book 1. The original Compact Disc digital audio (CD-DA) specification, developed in the late 1970s and introduced in the early 1980s by Sony and Philips. Audio sectors, tracks, and channels are speci- fled, along with other physical parameters. The format enabled up to 74 minutes of digital audio to be recorded at a sampling rate of 44.1 KHz, a rate that is sufficiently good to support the recording of clas- sical music. The Red Book was followed, in the mid- 1980s, by the. Yellow Book, which specified CD- ROM parameters. See Yellow Book. 2. In telephony, books in the lTU-T (formerly CCITT) 1984 series of recommendations. 3. The Adobe PostScript Lan- guage Reference manual. Red Box An environment for running Windows applications under Apple's Rhapsody on Intel-based computers and possibly on PowerPC-based computers, generally analogous to the Blue Box environment for running legacy Mac operating systems under Rhapsody. This would make it possible to have full compatibility with Intel-based operating systems such as Microsoft Windows on Apple hardware. See Blue Box, Yellow Box. red signalAn alert or failure signal or "stop" indica- tor used in many industries and in association with many different types of devices, networks, and gauges. See yellow signal for a fuller explanation or red and yellow signals. red wire A color designation used by mM to indi- cate wires used to establish a hardware patch to © 2003 by CRC Press LLC accommodate a code change. See blue wire, purple wire, yellow wire. Reduced Instruction Set Computing RISC. A type of programming and system architecture which uses a set of simpler instructions performing single, dis- crete functions to carry out an operation than would be used in a comparable operation by a Complex In- struction Set Computing (CISC) design. Most of the newer computers tend to incorporate RISC architectures, although not all support circuitry enables the full capabilities of RISC architecture to be used. Unlike clse commands, RISC commands are the same size, which means that less time is required for subsequent processing of the instructions, because individual evaluation of the commands for size and conversion to microcode is not required. When RISC software is compiled, it is evaluated to determine which operations are not dependent on the operation or results of others, and slates them for simultaneous execution. Due to the reduced instruction set and processing that takes place, the circuitry on RISC chips is simpler than on most elsc chips, resulting in a smaller physical size and, usually, lower heat output. Not all chips are strictly RISC or CISC. For example, in the Intel line ofprocessors, the Pentium chips are a transitional architecture that maintains some down- ward compatibility with the earlier CISC architectures, while still incorporating some of the advantages ofRiSC architectures. The chips tend to be larger and hotter than straight RISC chips, but meet a market demand through a transition period. redundancy Replication, duplication, superfluity, repetition. Redundancy is important in computing because the loss of data, whether stored or in the process of transport, can have serious consequences to human safety, economics, or business transactions. See redundant array ofinexpensive disks. redundant array ofindependent netports RAIN. ZNYX Network technology that provides a scalable, modular architecture for delivering high-performance, high-availability, customized intranet connec- tivity through clusters of network servers. RAINswitch server switches were announced in 1997 to support RAIN implementation in Fast Ethemetworks. redundant array of inexpensive disks RAID. A data storage, retrieval, and protection system using multiple disk storage devices, a system commonly used in networks. RAID consists of multiple hard drive storage devices linked together to provide data mirroring or data striping and parity-checking across disks in order to record the information redundantly. Duplication or data mirroring is primarily a function ofsoftware, whereas parity-checking requires a controller and is associated more closely with hardware. Many RAID systems are SCSI-based. A basic low-end RAID center may consist of four drives, each with 2.1 Gbytes ofstorage, sometimes set up in a rack, talking through a centralized controller system, usually through a server. Although a certain amount of storage is inevitably lost due to duplication of data, the big advantage of RAID systems is that they provide pretty good protection against data loss ifa drive goes down. There is less protection if several drives go down but, since this happens rarely and since companies are reluctant to back up data sufficiently often on systems like tape Redundant Array of Inexpensive Disks (RAID) - Level Specifications in Brief Level Notes Level 0 Striping, no redundancy or error correction. This can provide faster access, but does not protect data from loss. Levell Disk mirroring. Complete redundancy. Provides data protection. Level 2 Byte striping, dedicates at least one drive for parity information. Uses Thinking Machines, Inc. 's proprietary setup, which is not commonly used. Level 3 Generally used instead of level 2. Block striping will improve performance if data are written in large blocks and simultaneous reads are used. Distributed parity infonnation (originally required a dedicated parity disk, a stipulation removed in 1994). In other words, when appropriately implemented, better performance and data protection can be achieved. Level 4 Similar to level 3, but larger data blocks are striped across disks; each drive is not necessarily involved in each access. LevelS Block striping, parity information distributed across drives. At least three drives are required for a minimum implementation. Each drive is not necessarily involved in each access. Parity infonnation is also striped across disks. Provides data protection and, in many cases, will improve performance. This is a popular implementation ofRAID. Level 6 Not consistently specified or implemented. Level 7 Similar to level 4, with larger data blocks striped across disks. Uses Storage Technology, Inc. 's proprietary caching mechanism and operating system. 803 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary drives, the RAID alternative works well in ~ractice. Many RAID systems are "hot-swappable ' which means that an individual drive can be pulled out and replaced while the system is online, thus not neces- sitating a system shutdown or inconveniencing current users on the system. Specifications released in 1988 in the RAID paper proposed five levels. Since that time, changes and enhancements have occurred; the levels are not cut- and-dried since configuring various parameters, such as stripe size, creates overlapping characteristics between the different levels. Hybrid systems also ex- ist. Generally, however, to provide an introductory understanding, the RAID levels can be summarized as shown in the RAID Levels chart. In addition to redundancy and parity checking, a RAID system may have some intelligent monitoring incorporated into the system, which does periodic checks and analysis and reports anomalies to the controller. The controller can then signal a warning which allows the device administrator to check for potential problems, or swap out a drive before it fails. See dynamic sector repair, SMART. re-engineer To step back from a system or process, take a new look at it, and redesign it, sometimes from the ground up, usually with the intention of making it more efficient and cost effective. Software often has to be re-engineered, as legacy systems tend to be slower and less efficient over time, due in part to the way they are upgraded and, in part, because of tech- nological improvements and changes in hardware which are accommodated in a variety of ways. Mar- ket pressures also cause many software programs to be released before their time, in which case, they may be re-engineered before the next release. Work environments in companies that are growing or down- sizing quickly often must be re-engineered as the ways of organizing facilities and staff appropriate to a small company are not necessarily appropriate to a large company. reed relay switch A type of electronic telephone switch developed in the 1960s. Reed relay switches began to supersede crossbar switches, which were prevalent at the time, and some of the step-by-step switches still in use. Electronic switches opened up possibilities for many new types of caller services, such as Caller ID, Call Waiting, etc. reel-to-reel tape Magnetic recording tape wound onto separate round reels which are usually about 4-in. to 8-in. in diameter. Although most tape is now distributed on cassettes rather than reels, reel-to-reel is still used in some professional recording studios, especially if eight or 16 tracks are required for sound mixing and dubbing. Gradually these reel-to-reel sound recorders are being superseded by digital recording media. See cassette tape. Reeves,Alex H. A British engineer who is one of the significant pioneers of pulse code modulation (PCM) or, as he calls it, "coded step modulation." PCM is a fundamental quantization system used in audio recording and transmission technologies. Reeves con- ceived the idea while working at the International 804 Telephone and Telegraph Corporation (lIT) in Paris in 1937 and received several patents for the technology between 1937 and 1942. Reeves recognized the potential for PCM to counteract interference on transmitted speech communications. In 1965, Reeves authored The Past, Present and Future ofPCM. See pulse code modulation. reference clockA clock considered very accurate or stable, which is used as a reference for other clocks or processes, such as computer processes. Quartz crystal clocks are considered very accurate due to their vibrational properties and are often used in computers and watches. The speeds of various computer processes are described in clock cycles. Atomic clocks are used to establish Coordinated Universal Time and in satellite positioning systems which require accurate clock references. In multimedia editing environments, a reference clock is used to provide "house sync," that is, long- term synchronization of various audio or other signals, which resolve to the reference clock rather than to the time code signal. See atomic clock, chase trigger, Coordinated Universal Time, quartz crystal, time code. reference vectorequalization RVE. A derivative of transparent tone in band (TTIB) modulation and a basic aspect of linear modulation systems, RVE uti- lizes equalization for linear amplitude and phase correction to improve transmissions. It is suitable for trunked narrowband mobile radio systems, for example. RVE enables a digital radio to equalize a transmission signal at the receiver increasing potential schemes for high bit-rate densities. See linear modulation, tone in band. Referral Whois See RWhois. reflect 1. To rebound from, to bounce off of, to impact and move away from as a result of the impact. 2. To provide a replicate image of, to mirror. reflector/director elements On antennas, two or more protruberances from the main rod that are usually narrow and regularly spaced in an array. Reflec- tor and director rods help improve gain and directiv- ity ofbroadcast signals. See Yagi-Uda antenna. reflectometerA device for measuring surface reflectance, that is radiant flux, the reflected radiant energy per unit of time. This is useful for designing and testing reflective mirrors, parabolic reflectors, and other components that need to meet certain regulatory and operational standards. The instrument may be passive, measuring ambient reflectance, or active, sup- plying a light source (e.g., laser) and measuring the resulting reflection. See interferometer. reflectometer, optical time domain OTDR. A specialized reflectometer for locating and assessing possible sources of optical loss in longer fiber optic cables. The instrument emits a light pulse and converts and analyzes the reflections from the pulse. Depending upon the "echo" pattern, it may be possible to more closely identify the source ofa problem. refraction The change in the line of travel of an incident electromagnetic wave as it passes from one form of matter (or lack of matter, as in a vacuum) to © 2003 by CRC Press LLC another. At the point at which the incident radiant energy encounters and interacts with the changed environment having a different density and compo- sition, the energy interacts with the surrounding mol- ecules (or lack thereof) and its course is altered. See index of refraction for a full explanation. See bire- fringent; Ptolemaeus, Claudius. refractive index See index of refraction. refresh rate, scan rate The rate per unit of time at which information or an image is. The rate is usually dependent upon speeds that make it visible and in- telligible to humans. This phrase is frequently applied to broadcast and computer display technologies, especially cathode-ray tube (CRT) displays in which the action of electron beams on the phosphors is very limited and must be reinitiated (refreshed) in order for the image to continue to be visible. Refresh is a general concept which applies to many different types of situations in computing, from individual phosphor refreshes to graphical user interface element refreshes. The refresh rates of the phosphors on the inside coat- ing at the front ofa cathode-ray tube will affect the clarity and amount of flicker seen on the screen. Monochrome or gray scale monitors have longer per- sistence; that is, the image from the excited phosphors is visible longer, and thus do not need to be refreshed as often as color images. Refresh of the entire CRT image is described as the number of times per second the frame is redrawn. Refresh rates slower than about 20 to 40 frames per second are perceived as flickering to the human eye, especially if the image involves fast action. Still or slow-moving images do not need to be refreshed as often. The refresh rate of a computer program image is a combination of operating system and applications programming, and is not simply dependent on the hardware attributes of the system. In order to opti- mize speed on a computer display, the OS or programmer may choose to refresh only a section which has just been manipulated or changed. If the software does not keep track of what is transpiring on the screen or if several processes are active at once, it may seem that the display is slow to update or refresh a new window, gadget, or element drawn in a paint program. In general, quicker refreshes are desired over slower ones, but the cost of more computing power and faster hardware puts some economic constraints on the refresh rates of various systems. refurbished equipment Used equipment that has been serviced and tested by a technician to bring it back to original operating condition. If further work is done and substantial numbers of parts replaced or upgraded, it may also be referred to as remanufac- tured equipment. Refurbished equipment, or refurbs, are usually cleaned up and made to appear new or nearly new. Refurbished items are typically sold at a discount of about 15 to 30% over the price of new ones. regenerate To restore, bring back to original condition, recreate, duplicate. In electronics, signal regeneration is an important issue. Transmissions typically suffer from loss and interference over dis- tances, and any means that can be used to maintain a signal or regenerate parts or all ofa signal experienc- ing loss or change in some form is usually desired. There are many physical and digital schemes for re- generating systems. In some digital systems, regeneration may involve putting a signal back into its original form at the receiving end. In a sense, single sideband transmissions are a type of regenerated transmission, since only a portion of the signal is sent. The opposite sideband and the carrier signal are math- ematically constructed, and the original signal thus reconstructed at the receiving end. See regenerative repeater, relay, repeater, single sideband. regenerative repeater A type ofrepeater used in communications that are characterized by uniformity of length and signal to correct the timing of the signal and retransmit the cleaned-up impulses These are common in older teletype communications. See repeater. Regional Bell OperatingCompany RBOC. One of a number of companies which were formed by the divestiture of AT&T, which originated from the original Bell Telephone Company through a long, color- ful history of mergers and splits. In the mid-1980s Judge Harold Greene broke AT&T into seven RBOCs. For more detail, see divestiture, Consent De- cree of 1982, Modified Final Judgment. regional test bed RTB. Aregionally allocated location, lab, or systems setup that enables designers, de- velopers, or implementors to test their systems. Test ~JI;E:tf;t:;!;=:~~~ :lk:~rE~~:;: _ Test beds are important in almost every industry, since testing can be a complex activity involving specialized equipment and skills. Most designers and devel- opers don't have the resources to set up individual test beds. Test beds are often funded by universities, consortiums, and government grants, especially when they are designed to test products that have a big chance of promoting the common good or being commercially successful and widespread. register Arepository for data, a storage area which mayor may not also be used for data manipulation. There are many areas of telecommunications where registers are used. Many computer chip architectures have registers for holding information about to be moved or manipulated. Palette configurations for computer displays may be saved in color registers. Data modems have registers for setting various parameters, with Hayes AT command "s" registers common. Flags, configuration settings, etc. are stored in registers. Registration Number As part of the Federal Com- munication Commission's (FCC's)jurisdiction over equipment which may emit radiant waves that inter- fere with other equipment, appliances, radios, etc. There is a process of submission, evaluation, and cer- tification which warrants that the equipment has 805 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary passed FCC requirements. This Registration Num- ber is not related to quality, suitability for a particular use, or other usability issues; it simply confirms that the equipment falls within acceptable emission standards. Reis, Johann Philip (1834-1874) A German inven- tor who pioneered the transmission of tones and possibly also voice over wires. Reis accomplished this with various transmitters and other equipment that he developed and publicly demonstrated in Frankfurt to the Physical Society in 1861. No directly verifi- able evidence indicates whether voice was transmitted at the 1861 demonstration, but Reis' subsequent work indicates that he recognized the potential for voice communications and concentrated many of his efforts in that direction, eventually developing a telephone design that was not unlike telephones actually put into production in the United States some years later. Subsequent inventors, excited about the break- through, made improvements on Reis's early crude mechanisms, while Reis himself continued to study and improve the technology until his early death in 1874. See telephone history. relative intensity noise RIN. The ratio of the mean square optical intensity noise to the square of the av- erage optical power, frequently described in decibels (dB). A spectrum analyzer may be used to measure RIN. See Allan variance, Fourier transform. relay n. 1. To resend signals, objects, or communications to another node after which they are further transmitted or transported. 2. An electromagnetic device in a circuit for providing automatic control, which is activated by varying electrical impulses. A relay is usually combined with switches to control when they open and close, and widely used to auto- mate older telephone switching centers. Thus, it was important to design relays for durability, since they had to open and close circuits many millions of times. Because the relay is essentially a simple mechanism, it can be greatly varied by adjusting contact springs and windings, thus producing a large variety of types of relays. Multicontact relays were developed in order for numerous switching contacts to operate simul- taneously. See crossbar switch. Release to Pivot RTP. A number portability mechanism, similar to Query on Release (QoR), in which a telephone number that has been ported from a release switch returns the addressing information for routing a call (as opposed to the previous switch). If the number has been transferred, the information may be contained in the release switch or in an external database. See Query on Release. reliability An expression of the dependability of a system under actual conditions of use. See availability, mean time between failures (MTBF). Reliable Asynchronous Transfer Protocol RATP. A packet-based serial communications transfer protocol described by G. Finn in 1984. RATP is intended to facilitate reliable, easy-to-use communications between computers through public telephone circuits. Based on the ubiquitous RS-232 standard, RATP 806 enabled full-duplex, point-to-point communication more simply than some of the other protocols at the time as well as some capabilities not found in others. RATP is now considered a historic protocol. See RFC 916. Reliable Data Protocol RDP. A data protocol for providing reliable packet-based data transport services such as remote loading and debugging. It is, in part, adapted from Transmission Control Protocol (TCP), and was submitted as an RFC by Velten et al. in 1984. RDP supports the bulk transfer of data for various monitoring and control applications, as needed, with a simpler set of functions than TCP. Version 2 was submitted by Partridge and Hinden in 1990 to address some problems discovered in testing in 1986 and 1987. It makes changes to the protocol header and corrects some minor errors. See RFC 793, RFC 908, RFC 1151. Reliable SAP Update Protocol RSVP. A bandwidth- saving protocol developed by Cisco Systems for propagating services information. RSUP enables routers to reliably transmit standard Novell SAP packets only when a change in advertised services is detected by the routers. Network information can be transported in conjunction with, or independently of, the Enhanced IGRP routing function for IPX. reluctance Opposition, or resistance in a magnetic circuit against the creation of magnetic flux. Similar to the concept of resistance in an electrical circuit. See resistance. Contrast with permeability. REM 1. remote equipment module. 2. See ring error monitor. remailer Any online electronic mail transit station which changes or prep ends the header in such a way that the originating information is changed or ob- scured, or which intercepts mail and then forwards it on to its destination. Sometimes these remailers are LAN servers configured so that the header changes when incoming mail is served out to the local recipients. This is unfortunate in that the recipients cannot automatically reply to the sender and must manually type in the return email address in order to respond to their correspondents. This is not a recommended way of configuring a mail server and should only be done when a specific reason warrants it. Remailers are sometimes used irresponsibly. Thou- sands of get-rich-quick and commercial products pro- moters use remailers to obscure the origin of their online postings because there is much legitimate opposition to unsolicited commercial messages on public forums and in private email. Anonymous remailers are mail transit points which deliberately obscure the identity of the poster in order to ensure his or her privacy. See anonymous remailer, spam. remapping On a computer system, remapping is moving data, often in the form of blocks, arrays, or tables, from one area of storage to another. Memory remapping, address remapping, file location remapping, and keyboard remapping are some common examples. Remapping is sometimes used to double-buffer computer graphics screens - building © 2003 by CRC Press LLC a screen in a background while the current screen is viewed by the user and then displaying it by remapping the entire image to the video display area. It can improve the likelihood of fast, clean transitions. See frame buffer. remote access An important aspect ofnetworking in which access to computing services, devices, and information can be gained through a remote device on the network, usually a computer tenninal or phone line. On a phone line, remote access to an answering machine can enable a user to dial up the answering machine from a different phone, punch in some codes to see if there are messages available, retrieve those messages remotely, and even change the message on the answering machine through the phone line. Remote access does not imply the level ofoperations that can be accomplished, only that the device can be accessed in some basic way. Remote access terminals vary greatly in their ability to interact with a server or other user functions. For example, on a basic text- oriented "dumb terminal" connected to the main computer with a serial line, the user may only be able to execute simple text commands and won't be able to display graphics or run sophisticated applications locally. On the other end of the spectrum, some systems provide full access to remote applications, especially if they are connected with a fast transmissions protocol over fiber. In other words, there may be agraphi- cal database program available on the server that the user can run on a smart terminal as though the terminal was the main computer. Not all operating systems can do this. The X Window System is designed to provide this type of capability in conjunction with various Unix systems. It has also been upgraded to provide similar services over the Internet. See X Win- dow System 11. remote access concentrator RAC. A network system for interconnecting numerous multiple remote telecommunications links to a local system such as a local area network (LAN). Businesses with wide area networks (WANs) and telecommunications provid- ers make wide use of concentrators, as they aid in channeling and aggregating many types of equipment in order to serve broader needs such as large numbers of employees or telecommunications clients. High-perfonnance concentrators may support several services, including access, switching, and routing. Commercial RACs are created for many purposes such as interconnecting multiple ISDN B-channel lines to LAN s through Ethernet or multiple computer modems to TIIEI networks. Multiple RACS can sometimes be attached to one access switch. Depend- ing upon the protocols supported by a RAC, it may be connected indirectly or directly to the public switched telephone network (POTS). Many vendors promote asimilar product called a remote access server (RAS), which is basically a lower- end version ofa remote access concentrator (usually with fewer ports). Others refer to the operating software for a RAC as remote access server software. See remote access server. remote access control facility RACF. A facility dedicated to the provision and management ofremote access transmissions. An Internet Services Provider is a type ofRACF that provides multiple subscribers with remote access to Internet services. A telephone switching office is another type ofRACF, providing access to multiple remote telephones to its local subscribers. Within aparticular business, a remote access facility can be established as a management or security system to control, authorize, log, and secure data and physical resources (printers, modems, etc.) used by a variety ofin-house or contract employees. mM provides the commercially trademarked Remote Access Control Facility system, first introduced for mainframes in 1976. The system is promoted to businesses for the management and securing of valuable corporate data. RACF supports OS/390 and z/OS software systems. See remote access. remote access PBX Aprivate branch telephone exchange which can be accessed from an outside line with appropriate authorization codes. Once logged on to the internal branch system, various features can be used such as voice mail messages, long-distance calls connected and billed through the PBX, etc. remote access server The software and generally also the hardware on which the server software runs for managing transmissions between remote and local devices. Remote access to the Internet and off- site printers, security monitors, and other network- able devices can be facilitated by a dedicated server, especially in situations where numerous people will access the service through limited resources (e.g., a limited number of modems). See remote access concentrator. Remote Authentication Dial In User Service See RADIUS. remote batch processing A means ofsubmitting a computing job remotely to a processing system and receiving it back as or when the job is processed. This is rarely done at the consumer level, but it is still common for high-end mathematical calculations, scien- tific research, and other intensive computing applications which may require large amounts of computing time or more sophisticated computing resources. In the earlier days of computing, remote batch processing, especially with punch cards, was the only type ofservice available, and it could take hours or days to receive the results ofa simple calculation. Remote Call Forwarding A service in which a phone number is located in the central office of one exchange and any calls made to that number are for- warded (essentially by internally making a second call) to a line in another exchange. This may be of value to businesses that want to maintain a local pres- ence without the expense ofa local office, so that customers can call a local number instead of long- distance. remote concentration unit RCU. An off-site facility or device in which multiple devices/services of the same basic type are aggregated and handled together within one basic management device 807 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary housing. Telecommunications services (such as In- ternet access or cable TV) and electrical power distribution are two examples ofRCD applications. remote controln. A device to allow control of another device without making direct physical contact. The control of the device may be through indirect physical means (through a remote controller and cable), a network (computer-controlled vending machines in another part ofa building), or various wireless methods (infrared, FM, audible sound control, etc.). Remote control of computers on anetwork can be done through various telecommunications products, specialized remote applications and file serving software, or through operating systems which support this capability. remote control access RCA. Access to restricted areas, rooms, or pieces of equipment through wired or wireless remote devices. Many environments and types ofbuildings control access through remote devices. Examples include remote garage door open- ers, key cards, parking barrier remotes, audio/video/ computer components with security feature remotes and home automation remotes. remote diagnostics Systems diagnostics which can be run from a remote location. It is common for higher-end routing and switching devices on a computer network to be controlled through software at a main administrative location. This software typically permits the running of test and diagnostic routines and may show graphical diagrams of problems or potential problems or bottlenecks. On phone systems, diagnostic checks can sometimes be carried out with devices that generate specific tones or signals, which can initiate processes at the other end ofa phone line. remote me access RFA. A capability for accessing electronic files from asystem/terminal separate from the file server. RFA may be at some distance from the file repository. The Internet provides a transmission link to millions of file repositories around the globe that can be accessed and downloaded by various Web browsers and file transfer utilities. See File Transfer Protocol, ftp, Gopher. Remote Imaging Protocol RIP. A protocol for facilitating the implementation of EGA-resolution color images and mouse control from a remote system. RIP was developed to overcome the limitations of text-based bulletin board system (BBS) communications (in the days before the World Wide Web). Vector-based commands are sent and rendered through a point-to-point network connection. The system has some limitations but is an interesting so- lution to text-based remote terminal connections through dialup links. See Remote Imaging Protocol script language. Remote Imaging Protocol script language RIPscrip. Ascripting tool from TeleGrafix Commu- nications, Inc. for facilitating the development of graphical user interfaces for computer bulletin board systems (BBSs) supporting Remote Imaging Proto- col (RIP). It is a 7-bit system to maintain compatibility with the many 7-bit communications systems common through dialup connections (e.g., X.25). 808 RIPscrip works in conjunction with RlPaint and RlPterm for developing graphical interface screens and protocol needs. See Remote Imaging Protocol. remote job entry RJE. Generically, this is the entry ofcomputer commands from a remote entry terminal, that is, a local terminal, for execution on a remote machine (e.g., a timeshared mainframe). This applies to individual job requests and to batch requests. The term has changed meaning somewhat as computers have become more common and less expensive. Historically, remote job entry was a batch request submitted on computer punch cards. The cards were punched at acard-punching terminal by the programmer, then physically handed together as a"job" to a computer operator. The operator queued the job with others that were pending and then inserted the card bundle into the computer's card reader for execution. When the job was completed (or "crashed" due to errors), the operator would return the job cards to the programmer along with any relevant results (or error messages). These days, jobs are usually submitted electronically through software requests rather than physically through punch card stacks. See Re- mote Job Entry Protocol, remote programming. Remote Job Entry Protocol RJEP. RJEP was first submitted as an RFC by Chuck Holland in the early 1 970s. This generated quite a bit ofinterest and was corrected and developed further in RFC 407 in 1972. Remote job entry is a means by which a user can execute a computer processing job at a location (e.g., a mainframe) other than the local computer (e.g., a remote terminal). The user can thus submit ajob to another system acting as ajob server, which would process the job and deliver the results to the remote terminal through a TELNET connection. File Transfer Protocol (FTP) served as the file transfer mechanism. RJEP enables connections to be established indiv1du- ally or may leave the connection open for multiple submissions. See File Transfer Protocol, remote job entry, RFC 360, RFC 407. Remote Mail Checking Protocol RMCP. This low- overhead mail checking protocol was submitted as an experimental RFC by Domer and Resnick in 1992. It provides a client/server-based mail checking service. A program on the client's workstation uses RMCP to query aserver to see if new email has been received for a specific user. It is suitable for use with remote mail servers, such as those implementing Post Office Protocol (POP). The protocol is based on the User Datagram Protocol (OOP) port 50. Some authentication in the initial communication between client and server, at the cost of complexity. See RFC 1339. Remote Operations Service Element ROSE. An application layer service that provides the capability to perform interactive remote operations through a request/reply mode. ROSE is a generic information exchange technique which is not application-specific and not intended to define the operations it facilitates; this is left up to those implementing remote services. It is defined as ISO 9072-1, and as an X Series © 2003 by CRC Press LLC Recommendation by the lTV (X.219). See Abstract Syntax Notation One, X Series Recommendations. remote procedure call RPC. A means of making a request to a remote system so that it appears to the user as though the request is being fulfilled on the local machine. In other words, a user may open a word processing program and load in a file. The file may actually reside on a computer in another room or another city, but the user is unaware of any difference in using the file from the remote system or using a file from the local system as the RPC is transparent to the user. Another example would be the use ofa terminal communications program which accesses a modem on another computer as though it were physically attached to the local machine. A number of con- ventions for making requests to a remote system, and fulfilling those requests, have been developed. The RPC standard is a system for defining the parameters ofa remote communication. Remote Procedure Call Model RPC Model. Based on concepts of remote procedure calls (RPCs) in which the caller and called procedure are typically on physically separate systems exchanging data through a communications link, the RPC Model op- erates as a control mechanism functioning through the caller's process and the server's process. An RPC interface provides a set of remotely callable operations provided by the server and provides a means to manage server resources made available to the remote caller. As an example of one implementation, the caller sends a call message with parameters to the server process and holds for a reply. When a reply message is received, procedure results are extracted from the data and the caller resumes execution of local applications (or makes further calls). While the model does not exclude the possibility of concurrent processes on the part of the client and server, it is sometimes implemented with only one being active at a time. remote programming The capability whereby a system can be programmed from a remote location, ei- ther through a data network or phone lines, usually after input of appropriate authorization codes. Remote programming enables a field worker or telecommuter to administer a system without being physically present. In computing, remote programming is often done by BBS operators who want to check and manage their systems when out of town. By dialing their own BBSs and logging in as the Sysop, they can vali- date new users, check mail, configure the bulletin board, and accomplish various maintenance tasks through a phone connection. Remote programming is often implemented in high- end corporate and industrial software programs. The software is set up with security mechanisms so an authorized programmer working for the software vendor can dial into the customer's machine and do rou- tine maintenance, software tune-ups, diagnostics, and configuration without having to travel to the customer's site, and during nonbusiness hours, if needed. This type of service is usually provided through a separate service contract for a specified period, or is billed hourly, as needed. remote site A facilities or equipment location which is distant from the one presently occupied, or from which certain maintenance or administration tasks may be carried out. A sales representative with a lap- top, ascientist with an intercom radio doing field research, and a computer terminal in an annex building are remote sites often directly or indirectly com- municating with or through a main system at another location. Remotes sites may be fixed or mobile. remote switching center RSC. RSC has three generally accepted meanings: (1) a secondary telecommunications switch facility located at some distance from a main facility (at a remote location), (2) a switching center that is designed to serve remote subscribers who are often hundreds of miles away, (3) a switching center in a central or remote location that is remotely managed and controlled through telecommunications links from another center intended for that purpose. The first two meanings are traditional me"nings, established before sophisticated software and digital links were available, and are still relevant. The third meaning is becoming more prevalent as telecommunications networks such as the Internet make it prac- tical to configure, manage, log, and maintain switching services from a (remote) location off site from the actual switching facility. Spelling the third as remote- switching center helps prevent ambiguity with traditional meanings. Remote Telescope Markup Language RTML. Just as HTML is a markup language for representing information and handling user requests on the Web, RTML is a markup language for handling user re- :~~~~~~::~~~~~fs~ O::s~~~~~~s~~ special- '. RTML was initiated and has been adopted by the Hands-On Universe (HOU) Project as a proposed standard for users to send requests to observatory remotely controlled telescopes. RTML 2.0 was released by F. Hessman in May 2001. This version had changes and additions to RTML 1.1 and subsequently was refined by Denny and Downey. Denny then con- currently developed XRTML as an interim format; this came to be called RTML 2.0 while Hessman's fuller implementation, called RTML 2.0b, was re- named RTML 3.0. Objects were removed from RTML 2.0 to create RTML 2.1, which is specifically a request mechanism, with no support for the return of data. RTML 3.0, (released as 2.0b in July 2001) fully specifies a two-way communications protocol for submitting, updating, and acknowledging astro- nomical data requests, and for returning status information and data related to these requests. See Robotic Telescope Markup Language for the events leading up to RTML. remote terminalA local computer terminal that enables remote access to services or accounts not available on the local terminal. Thus, a remote terminal in a branch office could be used to communicate with a centralized databank in the main office, for example. Remote terminals may be wired or wireless, 809 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary or may be connected through a combination of wire- line and wireless services (e.g., from the terminal to awireless access concentrator to asatellite link to the main office). Remote terminals are often classified as dumb or smart terminals. In general, dumb terminals are those which have limited capabilities and may have few applications that can be executed locally. Dumb terminals are used in situations where cost or security are concerns. Smart terminals are those that have significant functionality on their own, even if not connected remotely to another system. Remote User Telnet Service A means by which a specific service ofUser Telnet may be accessed by opening a port connection (107), a mechanism sug- gested by M. Mulligan and submitted as an RFC in 1982 by Jonathan Postel. This enables remote access to another system for logging in and executing commands. It is now considered a historic service. See RFC 764, RFC 818. remotely piloted vehicle RPY. A land, water, air, or space-based vehicle piloted from a remote location, usually through radio control signals (though other methods are theoretically possible). Military drones, children's toys, and robots may be controlled this way. removable media Storage cartridges, drives, or diskettes which can be swapped out and replaced with another. This provides a less expensive, portable op- tion to numerous fixed storage devices. In the mid- 1990s various cartridge drives became very popular, as it was possible to store from 100 to 1000 Mbytes on a cartridge not much bigger than a floppy. The problem was that every cartridge drive had a different format and the formats were not intercompatible. More recently, super diskettes have been introduced, which use normal floppy-sized disks that can store 100 MBytes, but the drives are still downwardly com- patible with 1.44 floppies, so that it's not necessary to have several devices attached to the computer. It is not clear, as of this writing, which of these technologies will prevail or whether another new one wi II leapfrog them before one or the other is firmly established. REN See Ringer Equivalence Number. REO removable erasable optical. repeat dialing This is both a function of some phones and telephone/computer software programs, and a service of some phone companies in which a number found to be busy can be repeatedly dialed until the connection goes through, without the user dialing the number again. Repeat dialing is very commonly used in telecommunications software programs to dial up BBS numbers that are frequently busy. repeater A device for receiving signals and retrans- mitting those signals in order to propagate or amplify the signal. Repeaters are commonly used in technologies with signal attenuation and fade. Repeaters are used in digital and in analog systems and are often spaced at intervals over paths that cover long-dis- tances. In digital systems, it is possible to reconstruct the informational content of the signal; in analog 810 systems, more often the signal is amplified, which means that accumulated noise and degradation are still limiting factors. Radio broadcast repeaters and microwave repeaters are examples of common imple- mentations. In networks, a number of devices assist in the conversion and propagation ofsignals (bridges, routers, etc.). Arepeater is simpler than most of these devices, serving only to continue the signal and extend its range, or to clean it in its most basic sense, rather than to change the informational content of the data. See amplifier, bridge, doping, regenerative repeater. Repeatered Submarine Fiber Optic Cable Systems RSFOCS. Amarket study on underwater fiber optic cable systems published spring 1999 by IGIC as an update to a previous study. reperforator An instrument that translates received signals into ageometrically coded series oflocations that are punched or otherwise impressed onto a paper tape. Early telegraph systems and most of the early computing devices used reperforators. These were then read with optical or tactile sensing devices to turn the code back into human-readable form. See chad. reperforator/transmitter RT. A teletypewriter device which includes both a reperforator for punching received codes on paper tape, and a tape trans- mitting unit for sending the codes to a tape punching mechanism. repetitive pattern suppression RPS. A means of data optimization which compresses digital communications by removing repetitive patterns and reproduc- ing them at the receiving end. replication A process commonly used on computer systems for security, redundancy, distributed access, or other backups. In large companies and on the In- ternet, whole file archives are often replicated or mir- rored in order to provide access at areasonable speed to a larger number of uses. Replication of data is a means to protect data in case of a serious problem with a system or storage device. RAID systems are a means ofreplicating data to preserve data in case of a fault. Replication in the form ofregular backups is recommended for all important computer data that need to be preserved. In radio communications, transmissions are sometimes repeated to improve the chances ofa message getting through. The replication may be ofindividual small units oftransmission or may be repetition ofa short message or signal. See ALOHA. reprography Copying and replicating. REQ request. Request for Comments RFC. Asignificantly influ- ential, formatted, open communications forum for technical experts which accepts, edits, numbers, pub- lishes, and disseminates Internet-related documents including protocols, draft and official standards, no- tices, opinions, and research. Known as RFCs, these electronic documents form a body of more than 2200 contributions that provide a remarkable overview of the evolution of the Net, its structure, functioning, and philosophies. © 2003 by CRC Press LLC There are a number of categories of RFCs. Some of them are tiered and cannot be submitted without pass- ing through previous categories in a specified order, with specified waiting periods for comments and re- visions from the RFC community. RFCs are not changed once they have been submitted, assigned a number, and distributed. Any changes regarding an RFC must be submitted as a new RFC. There are many excellent RFC repositories on the Internet, with good indexes and abstracts. Anyone can submit an RFC provided it is topical and follows the official format and procedures. This dictionary includes references to specific RFC numbers where the author felt the technical origin of the information would be of interest, and there is an overview of significant RFCs in the Appendix. For information on submitting RFCs, see RFC 1543. Request for Discussion RFD. Similar to a Request for Comments (RFC) in that it is a means on the In- ternet to solicit and generate discussion on a specified topic. However, it focuses on intercommunica- tion on a topic in a slightly less formal or definitive manner as opposed to specifying or defining a topic once certain conclusions or draft/final working mod- els have been developed, as in RFCs. RFDs often pre- cede RFCs but do not necessarily result in RFCs. See Request for Comments. Request for Information RFI. A solicitation and notification of interest in receiving feedback or information on a specified topic, product, or process, without implying that the requester necessarily wishes to purchase or use that for which the information is solicited. See Request for Comments, Request for Discussion. Request for Proposal RFP. A call for proposals for solving a problem or participating in a project. ARe- quest for Proposal process is used by many institutions to initiate a project such as building a facility, setting up a new organization, or developing a new product or service. People who submit RFPs usually have a community or economic interest in shaping or otherwise participating in the project. A Request for Proposal mayor may not be accompanied by a Request for Quote. See Request for Quote. Request for Qute RFQ. A call for monetary quota- tions for a particular project or venture. The RFQ process is commonly used by institutions to assess various aspects of implementing a project and what that project will cost. Vendor input in the form of Code (no code) I H E PS DS S Category Unclassified Informational Historical Experimental Proposed Standard Draft Standard Standard RFQs not only provides information on the price, but may also give some idea of the time line and type of materials involved. It also serves as a fonn of preliminary contract (and is sometimes the only contract) once a vendor has been selected to undertake ajob. An example ofa simple RFQ would be a faxed page explaining that the cost of purchasing and installing a new modem might be $200. An example ofa more complex RFQ would be a 12-page document detail- ing the costs involved in setting up a video security system in a business office or factory that can be monitored and controlled (through pan and tilt con- tro Is) from a remote location through the Internet. A Request for Quote may accompany a Request for Pro- posal or may sometimes be combined with a Request for Proposal. See Request for Proposal. reroute To make a temporary or permanent change in a data path. Rerouting frequently occurs in large, dynamic networks like the Internet. Systems where rerouting is common usually use a hop-by-hop method of routing in order to accommodate changes and to create new paths as needed. In electronics, rerouting ofa circuit may be accomplished by a patch or shunt, a wire which bypasses the original path. On Fiber Distributed Data Interface (FDDI) networks using dual rings, rerouting to the second, backup ring is carried out ifa problem is detected on the primary ring. RES 1. regional earth station. 2. See Residential En- hanced Service. Resale and Shared Use decision A decision of the Federal Communications Commission (FCC) to allow competition in value-added networks. resampling The process of subsequent sampling of data, as image or sound data, and re-encoding it. Re- sampling usually occurs when the original sample was not of the resolution level or compression rate desired. Resampling may also occur in order to update or refresh information that may be changing, as in Internet videocam shots, videoconferencing, etc. See sampling. research and development R&D. The study and associated development oftheories, sciences, and technologies. In communications, much R&D focuses on creating marketable products. R&D often consumes a huge proportion ofa startup business's budget. Many large corporations have R&D facilities to enable them to develop new products, including ffiM, Lucent Technologies (Bell), and Xerox. In many cases, R&D does not directly result in products that can be manufactured and distributed, but the process of R&D indirectly contributes in surprising ways or, sometimes, decades later, when manufac- turing processes or needs change or catch up to the theories. As an example, Charles Babbage's historic analytical engine (a pioneer computer concept) research and design was apparently theoretically sound, but the technology to build his machines did not ex- ist during his lifetime. As a more recent example, space research has resulted in many portable and wireless communications technologies that might not have developed otherwise. 811 © 2003 by CRC Press LLC . 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary passed FCC requirements. This Registration Num- ber is not related to quality, suitability for a particular use, or other usability issues; it simply confirms that the equipment falls within acceptable emission standards. Reis,. Protocol RATP. A packet-based serial communications transfer protocol described by G. Finn in 1984. RATP is intended to facilitate reliable, easy-to-use communications between computers through public telephone circuits. Based on the ubiquitous RS-232 standard, RATP 806 enabled full-duplex, point-to-point communication more simply than some of the other. device 807 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary housing. Telecommunications services (such as In- ternet access or cable TV) and electrical power distribution are two examples ofRCD