Fiber Optics Illustrated Dictionary - Part 84 doc

Fiber Optics Illustrated Dictionary ROM I. See read only memory. 2. rough order of magnitude. Romer, Ole (Olaf) Christensen; Rumer, Ole Christensen (1644-1710) A Danish astronomer, physicist, and scientific instrument-maker who, in 1675, demonstrated the velocity oflight as II minutes per astronomical unit (AU) based upon obser- vations of the planet Jupiter and its moon 10. In the 1660s, he studied with Rasmus Bartholin at the Hafnia (Copenhagen) University and was entrusted with the editing of the great scientist Tycho Brahe's manuscripts. He was appointed in France by Louis XIV to tutor the Dauphin in astronomy, and also was appointed as the Astronomer Royal at the Danish court ofChristian V. !Wmer invented a new type of thermometer and com- municated some of his ideas to D. Fahrenheit in the early 1700s. In Denmark, he introduced a new system for numbers and weights that combined the concepts of weight and length. See Bartholin, Rasmus. Ronalds, Francis (1788-1873) An English re- searcher who was a pioneer in modem telegraphy, Ronalds developed a frictional telegraph, using above-ground copper wire that he demonstrated ca. 1816, more than two decades before Wheatstone and Cooke in England and Samuel Morse in America developed the first widely known telegraph systems. Ronalds also experimented with other types of telegraph systems. Charles Wheatstone corresponded with Francis Ronalds around the time he developed a telegraph with w.F. Cooke. The British Navy failed to adapt Ronalds' telegraph system, choosing instead to continue their "tried and true" semaphore system of signaling. See Schilling, Pavel Lvovitch; Morrison, Charles; Wheatstone, Charles. Ronchi gratingA series of perfectly straight lines im- pressed into glass, acrylic, or other film surface. It is aspecific type ofdiffraction grating in which the distance between the grating facets and the facets themselves are the same. When placed near the focal point of an incident beam oflight, imperfections in the optical system will be revealed as deviations from the straight line Ronchi reference grating. This makes it suitable for testing optical components when used in conjunction with a diffuser for providing an even lighting source and, optionally, Ronchigrams, for comparison of the results to reference ideals. See dif- fraction grating, Ronchi test, Ronchigram, star test. See knife-edge focusing. Ronchi test A way to test the optical quality ofa traditional lens such as a telescopic mirror lens by using a Ronchi grating, with evenly spaced, straight lines as a reference against which aberrations in the optical system can be seen. In general, the tester is placed at the center of the point ofcurvature ofa mirror, the reference light passes through a diffuser, then through the Ronchi grating, and reflects from the mirror at least once. The reflected light then passes through the grating to the eye of the observer or it may be projected or stimulate an imaging surface (e.g., a computer peripheral). The Ronchi test can be set up at home or in a scientific lab. 822 It is relatively straightforward to test flat optical reflec- tors with a Ronchi test, as aberrations will manifest as curved, turned in, or out-of-focus areas. If parabolic shapes are assessed, the resulting image (which may be curved) can be compared against an image of the ideal band pattern associated with the shape under test at a specified distance and angular orientation to the Ronchi grating. A Ronchi test may be followed up by a star test. See Dall test, double-pass autocollimation test, Ronchigram, star test. Ronchigram Reference Images rnJ]t)J(t ((I)) ~)I(e~I~(I) A Ronchigram is a reference image for comparison to light patterns from a reflective surface that have been reflected through a Ronchi grating. The top left image is a reference image for a regular mirror ori- entedflat in relation to the plane of the Ronchi grating. This isfairlyeasy to visualize and intuitively com- pare. The other images can indicate aberrantpatterns for a supposedlyregular mirrored slllface or they can serve as references for other shapes, such as pQl'abo- laid mirrors. which are notas easy to intuitively check. For nonflat surfaces. the distancefrom the reflective surface to the Ronchi mirror becomes important if it is to be checked against a reference Ronchigram. A chart of Ronchigrams may also be accompanied by surface deformation diagrams for mirrors or lenses that correspond with particular Ronchigram shapes. Ronchigram, Ronchi pattern A banded reference image that represents an expected pattern of light reflected through a Ronchi grating from a reflective optical surface such as a telescope mirror. It is possible to carry out a Ronchi test on a basic flat mirror without Ronchigrams, because aberrations will manifest as curved lines or fuzzy areas that can be readily seen, but when testing parabolic or other nonflat surfaces, there are more variables to control and the distance from the mirror, its orientation, and its shape may change the test results to manifest as a wide variety of patterns that can't always be intuitively assessed without a reference image. Computer software can be used to predict the Ronchi pattern, at a given distance, for areflective surface ofa given shape. See Foucault test, Ronchi grating, Ronchi test. Rontgen, Wilhelm Konrad (1845-1923)A German physicist and educator who developed the vacuum tube (1895), the fluoroscope, and pioneer experimental © 2003 by CRC Press LLC studies in X -ray emissions in industrial radiography and medical radiology. He was the first recipient of the Nobel prize in physics. The roentgen unit ofX- radiation is named after him. See roentgen, X-rays. root mean square (abbrev. rms) The effective value ofa quantity in a periodic circuit, measured through the duration of one period. root name server On distributed computer networks, name servers provide a means to administer the transmission and routing of data among source and destination computers. Name servers are a type of address allocation and identification tool. Initially, the name servers handling root zones (indicated with a dot) also handled top-level domains (TLDs) such as the . com domains. However, due to the growth of the Internet and differences in administration of root name servers and TLD servers, it was proposed in the mid- 1990s that a distinction be made between the two groups as the performance needs of root servers were felt to be greater than for many other types of servers. It was further proposed that requirements be for- mally laid down for root name servers so that vendors and implementors would have appropriate tools for handling the more stringent requirements of root name servers. See Domain Name Server, RFC 2010. ROSAT RBntgen Satellite. A research satellite that has expanded knowledge of the universe and past events in this galaxy by aiding in discovering local hot X-ray plasma. ROSE See Remote Operations Service Element. Rosenbliith,ArturoA physiologist who collaborated with Norbert Wiener in investigations in artificial intelligence and self-organizing systems, much of which was documented in Wiener's book on cyber- netics. Ross test See Dall test. rotary dial In telephony, a circular dial mechanism typically activated by placing a finger (or pencil end) in one ofa series of punched out holes, and turning (dialing). The mechanism springs back to its original position after each selection. The alphanumeric selections are displayed under each associated hole. Turning the dial activates the telephone carrier's elec- tricalloop for specified intervals that form a simple code to identify the number dialed. Dials were not always circular. Some of the earliest dials consisted of levers, resembling the front of a small slot machine. Rotary dials are normally associated with pulse dialing signals. Rotary phones are steadily being superseded by pushbutton phones. See pulse dialing, tone dialing, keypad, touchtone phone. rotary hunt A means of routing selection for a call that has been placed in a multicircuit hung group. The system cycles through circuits, hunting for an idle one through which it then routes the call. rotaryswitchA commercially successful electrome- chanical telephone switching system developed in the AT&T labs in the early 1900s, based on Lorimer one- step selection concepts and incorporating a perma- nently rotating motor. These were installed in Europe as a result of an International Telegraph and Tele- phone buyout of Western Electric's International di- vision in 1925. See Lorimer switch, panel switch, rotary switch. ROTL Remote Office Test Line. A means of automatically testing telecommunications trunk lines from a remote location through a hardware switch. The remote testing may be conducted manually, through a control unit, or through automated Central- izedAutomatic Reporting on Trunks (CAROT). Round Robin RR. A scheduling or resource-allocation system that "divvies up" tasks or resources more or less equally among all the participants in a generally cyclic pattern. Thus, a Round Robin system in a classroom with only one computer could be set up to allocate an hour to each student in a repeating rota- tion through the school year. In general, Round Robin systems deal with discrete events or resources that do not overlap (though there may be exceptions). A chain letter extended by each member in the chain and returned to the source when it is completed is another example. Many sports use Round Robin systems (tennis, pool, bowling). They provide each player with the oppor- tunity to play every other player. Round Robin systems have been used by humans for centuries (maybe even tens of thousands of years) for scheduling work and play and for providing fair access to resources on arotating basis. The Round Robin system, as we now understand it, is at the heart of many scheduling algorithms that use the same general cyclic event-driven concept. Round Robin systems are used to allocate computers, modems, printers, and many other heavily accessed systems ~i~;r;i~::; i~~~~~;r~~~~I~~~:1f~:~ i. of people or multiple Round Robins intended to take place concurrently. Other common Round Robin applications include • token passing in a Token-Ring network. The token moves around in a circular topology to each machine in the ring, • network routers such as the Cisco CSS 11800, that use Round Robin algorithms to handle data flow, • telemarketing systems that assign incoming calls to available agents on a Round Robin basis, especially in situations where the agent is earning a commission and wants a fair share of the calls, and computer operating systems running multiple processes in which the computer moves on to the next process if the previous process has completed, but may preempt a process if it is not completed after a certain amount of time. Weighted Round Robin schedules take into account the unequal capacities of different participants or processing systems. For example, in a telemarketing firm, if there is a crackerjack sales representative with seniority who always closes a sale, the Round Robin system of assigning incoming calls might be weighted 823 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary to go to this sales representative more often than the other agents. Thus, the sales representative is happy and stays with the company and the company is happy because profits are maximized. Weighted systems tend to have the advantage of being more effective in systems with unequal members, but also have the disadvantage of being controversial when they in- volve people rather than computing processes. See queuing, Token-Ring network. Round Robin, DNS A load-balancing resource-sharing system implemented on the Internet through recent version DNS/BIND 4.9 (Domain Name System with BIND) that arose in part because of heavy access to favored sites on the World Wide Web. This enables a cluster of servers to provide client requests to a very large number of users by allowing address records to be duplicated for a host, with different In- ternet Protocol (IP) addresses. The name server can then rotate in a Round Robin fashion through names with multiple address (A) records. The DNS/BIND implementation is not robust in terms of handling server failures, as the Round Robin system is inherently intolerant of missing links in the pool of resources, but other programs can be used with DNS/BIND to handle possible server failures. See Berkeley Internet Name Domain, Domain Name System, Round Robin. round trip delay RTD. A general phrase that refers to a number of aspects of network physics and be- havior that contribute to delays in the full path back to the sender. It is a statistical measure useful in installing, configuring, and tuning networks. Some delays are evaluated in relation to what the elapsed time should theoretically be and some are evaluated relative to a test suite of alternate configurations. Sources of delay include the physical length of the path, the media and protocols used to send the information, data processing, compression and error-checking, data congestion, and even the speed oflight itself. route 1. n. Path taken by data or other transmissions. See traceroute. 2. v. To delineate a communications path. This may be fixed before the transmission or may be dynamic according to availability and load levels evaluated en route. See hop-by-hop. Route Access Protocol RAP. An open distance-vector routing protocol for distributing routing information through Internet-connected systems ranging from large Internet Service Provider (ISP) systems to local area networks (LANs). The protocol was submit- ted as an RFC by R. Ullmann in 1993. The Route Access Protocol is a generalized protocol, making no distinction between external and internal networks and is designed to accommodate both small and large systems. RAP is internally IPv7 -compliant but is downwardly compatible with IPv4 networks. Distance-vector routing was selected for RAP to promote scalability. The protocol operates on TCP port 38 through a symmetric connection between RAP ports. Through peer discovery, it may also be used on User Datagram Protocol (UDP) port 38. RAP propagates routes opposite to the direction of the path of the datagrams using the associated routes. Source 824 restriction may be invoked to provide a certain measure of security and must be added to routes if security filters have been established in the Internet Protocol (IP) forwarding layer. Once a connection is established, RAP peers need only send new or changed routing information. The routing information is purged by each system when the session ends. See RFC 1476. route diversity An architecture providing anumber of options in routing a transmission. This may be or- ganized in a number of ways, depending upon the type of network, the load on the network, and the existence and quantity of redundant circuits. Route diversity can be as simple as an extra line to take the load if the primary line goes down or as complex as dynamic hop routing in a distributed computer network. route flap, router flap A fault condition in which changes in routes propagating across a network (usually from losing one or more nodes) exceed the capacity of a router's processor and memory to cope with the change, and consequently impact its ability to route. Routers are generally selected to well exceed the number of routing paths expected to be needed to prevent this serious problem. router 1. A device or mechanism for selecting a path. 2. In a simple network, an interface device which se- lects a path for the transmission packets. In layered networks, the router typically functions at layer two or layer three, dependin R upon the degree of auto- mation and "intelligence' built into the router. There used to be somewhat ofa distinction between routers and switches, but switches are becoming so sophisticated that the distinction is disappearing. Rout- ers frequently include routing databases, in addition to algorithms to dynamically select routes. See bridge, switcher. router, ATM In ATM networks, a router delivers and receives Internet Protocol (IP) packets to and from other systems, and relays IP packets among systems. Routers vary in sophistication, with some able to contribute significant network management functions, such as priority and load balancing. They can be protocol-dependent or protocol-independent. Also called an intermediate system. See LIS. router, Frame Relay A Frame Relay-capable router has the ability to encapsulate local area network (LAN) frames in Frame Relay-format frames and feed them to a frame relay switch, as well as receiving frame relay frames, and stripping the frame relay frame to restore the information to its original form, passing it on to the end device. With improved technologies, the distinction between routers and bridges is lessening. Even switches now have many of the capabilities of routers. See bridge, gateway, switch. routing Selecting or establishing a path. In telecommunications, the path may be used to transmit super- visory signals and data (either together, separately, or over separate paths). Routing may be static or dynamic. Dynamic routing is typically used in larger networks, especially those with individual systems in the path that mayor may not be available at any given time. Static routing is suitable for small or local © 2003 by CRC Press LLC systems, or for those carrying priority or secured transmissions. routing aggregation An administrative tool for organizing and optimizing the use and availability of routes to deal with the continually rising demand on networks. Users are encouraged to return unused addresses, and old addresses are assigned prefixes so multiple routes can be aggregated into one. Routing Arbiter Database RADB. Arouting database established by the Routing Arbiter project. One of several databases in the Internet Routing Registry. Routing Arbiter ProjectANational Science Foun- dation-funded project given the task ofcoordinating routing for the new NSFNet architecture in coopera- tion with a number ofeducational and private busi- ness concerns. Route Servers were to be installed at connection points to reduce the need for peering. Due to NSFNet legacy database information, a number of large providers have shunned the Routing Arbiter and the project has changed to a service available through some of the Public Exchange Points. See peering. routing code 1. In telephone communications, the area code. 2. In U.S. postal communications, the last four digits of the ZIP+4 code. 3. In networks, the data parsed by the router or switcher to establish apath to the intended destination. routing computations, routing algorithms Math- ematical schemes to compute efficient routes through a network. The algorithms may be straightforward if the topology and size of the network are known and are relatively stable. The situation is more compli- cated on the Internet, which is extensive, encom- passes many different types of configurations, and which changes constantly as networks are added or changed. routing domain RD. In ATM networking, a collec- tion of systems that have been grouped topologically within one routing system. routing information base RIB. Astatic or dynamic table of routing paths maintained within arouter or a processor/memory system associated with a router. In distributed networks, in which systems may be added or removed dynamically, RIBs are generally updated dynamically as the information about the changes propagate through the network. Routing Information Protocol RIP. A very common routing protocol from a family ofprotocols known as the Interior Gateway Protocols (IGPs). RIP evalu- ates the path between two points in terms of hops between the source and destination points. Each hop in the path is assigned a value which may be incre- mented by the router and entered into the routing table. The Internet Protocol (IP) address becomes the next hop. In order to prevent continuous routing loops, a limit is defined for a path's hop count. If the routing table entry exceeds the maximum hop count, the destination is considered unreachable. See RFC 1058, RFC 1723. Route Servers Specialized servers from the Routing Arbiter project intended to hold clearinghouse routing information in a Routing Infonnation Base at each network interconnection point in order to eliminate, or at least reduce, the need for peering. These servers are not intended to actually transmit the traffic, but serve to handle the flow ofinformation concern- ing pathways. routing table, data network In data networks, a table detailing paths to specific Internet Protocol (IP) addresses. With the explosive growth of the Net, the number of paths, and hence the size of the tables, can become very large. Primary routers sometimes list more than 25,000 routes and the routers themselves must be designed to keep ahead of capacity. Discus- sions are ongoing as to the benefits and problems in various assignments of routing paths, with provider- based routing being favored due to greater ease of implementation, and geographic-based routing proposed because it has less ofa tendency to con- centrate power in the hands of a few large providers. routing table, telephone network In telephone communications, routing tables serve to record and provide information for the processing of incoming calls. Thus, calls may not just go to aparticular caller or workstation, they may be directed to automated voice services, voicemail, queued holds, recordings, etc. They may require the capability of stepping back through the route as well, depending upon the sophistication of the system and the selections available to the user. Routing Table Maintenance ProtocolAn AppleTalk network routing protocol that is based upon Internet Protocol (IP) Routing Information Protocol. RTMP is atransport-layerprotocol that manages routing information within an AppleTalk router and facilitates the exchange ofrouting information among Apple- Talk routers to help keep the information current. Hop count is used as the routing metric for RTMP. The RTMP table includes information on the hop count to a destination network, the appropriate router port, the next hop router address, the status of the routing table entry, and the network cable range of the destination network. See Routing Information Protocol. Routing Table Protocol RTP. Anetwork communications routing protocol from Banyan System, Inc., VINES (Virtual Networking System). RTP is based upon Internet Protocol (IP) Routing Information Pro- tocol. The protocol facilitates the distribution of network topology information among the various servers and enables servers and routers to identify others nearby. It works in conjunction with other protocols such as the Address Resolution Protocol (ARP). See Routing Information Protocol. routing update Network configuration information provided by a router and, in some cases, costs associated with use ofparticular routes. Routing updates can be scheduled to be automatically sent out at specified intervals, and are typically broadcast ifsignifi- cant network configuration changes have been made. row 1. Generally, about three or more elements more or less lined up in one directional plane. 2. In a 2D system, the grouping, between the left and right bounds, of more or less horizontally aligned elements arranged within agrid or tabular format. This mean- ing of the word is commonly used to describe screen 825 © 2003 by CRC Press LLC A null modem cable can be made from an RS-232 cable by swapping pins 2 and 3 on one end of the connection. This enables two locally connected computers to network through the cable with suitable communications programs running on each system. The initial RS-232 standard was superseded in 1987 by the standard defined by the Electronic Irldustries Alliance (EIA) as EIA-232-D, which was followed in 1991 by the EIA/TIA-232-E. RS-232c is similar to the ITU- T Recommendations for V.24 and V.28. duced in the early 1960s. RS-232 is widely supported on desktop computers and other devices commonly used for communicating with modems, remote terminals, and printers. RS-232 specifies the electrical and physical characteristics of the connection. The most common implementation is RS-232-C (which is often transcribed as RS-232c for brevity) and many in the industry mean RS-232c when they say RS-232. The RS-232c specification defines a way to connect data terminal equipment (DTE) with data circuit-terminating equipment (DCE). Most systems support RS-232c through a 25-pin D connector (DB-25), although fewer pins can be used to implement the specification, and 9-pin Dconnec- tors are sometimes used (or 25-pin connectors with some of the pins unconnected). A few systems specify more than 11 or 12 pins (pin 12 is not part of the spec. but some vendors assign a proprietary signal to the pin). The basic RS-232 pinouts more or less commonly used by manufacturers are as follows. The most important pins for establishing a basic connection are noted with asterisks and a minimal connection would require transmit, receive, and ground. Fiber Optics Illustrated Dictionary locations or positions within a spreadsheet or printed medium. See column. Royal Society An independent national academy of science, founded in 1660 to support the British scientific community. The Society funds research, stimulates international communication among sci- entists, hosts conferences, produces reports and jour- nals, and maintains one of the most remarkable historic archives of scientific endeavor in the world dat- ing back to 1470 (which includes records and photos of many of the major advances in computing and telecommunications). Among its publications is the Philosophical Transactions of the Royal Society which was first printed in 1665. The society has recognized scientific achievement through awards since 1731. http://www.royalsoc.ac.uk/ RP See Restricted Radiotelephone Operator Permit. RPC See remote procedure call. RPE radio paging equipment. Systems that use radio waves to send a signal to a receiving unit. The signal may be a simple pulse to trigger a light, vibra- tion, or sound, or it may contain information that can be printed out on a text-capable paging device. RPG 1. Report Program Generator. A computer programming language for processing and displaying large data files. 2. See role-playing game. RPM Remote Packet Module. RPN reverse Polish notation. A mathematical notation system in which the values to be operated upon are entered first, followed by the operation to be per- formed. In other words, multiplying two numbers would be done like this: 2 [enter] 4 [enter] * (times) which would display the result as 8 This system is used on HP calculators and others commonly used by the scientific community. Calculators marketed to the nonscientific community tend to use regular notation as follows: 2 [enter] * (times) 4 [enter] = (equals) which would display the result as 8 Those who use one system often curse when they encounter the other, because it necessitates shifting mental gears to enter data and operations in the cor- rect order. RPOA See Recognized Private Operating Agency. RPOP Remote Post Office Protocol. See Post Office Protocol. RPS See repetitive pattern suppression. RPTrepeat. RPV See remotely piloted vehicle. RQS See Rate Quote System. RR 1. radio regulation. 2. railroad 3. return rate. 4. See Round Robin. 5. rural route. RRSF RACF remote sharing facility. See remote access control facility. RS 1. radio satellite. 2. recommended standard. See RS-232 for an example using this prefix. 3. remote station. 4. reset. 5. See Royal Society. RS-l Along with RS-2, the first USSR amateur sat- ellites, launched in October 1978. RS-232 Recommended Standard 232. A decades-old single-ended standard for serial transmissions intro- 826 Pin 1 2* 3* 4* 5* 6 7 8 9 10 11 12 15 17 18 20 22 24 Abbrev. GND TxD RxD RTS CTS DSR GND DCD +12 -12 AUD AUD DTR RI Function earth ground transmit data receive data request to send (control signal) clear to send (control signal) dataset ready (signals that the device is on) signal ground data carrier detect (signal that carrier is on) DC voltage (Amiga) DC voltage (Amiga) audio out (Amiga) transmit clock receive clock audio in (Amiga) data tenninal ready ring indicator auxiliary clock (provided by some vendors for local connections) © 2003 by CRC Press LLC The single-ended handling of voltage in the RS-232 specification limits transmission distances to about 50 feet or so. For longer distances, it is preferable to use balanced pair voltage formats like RS-422, to transmit up to about 4000 feet. See RS-422. See EIA Interface Standards for a list of common standards. See Selected Overview of Recommended Standards for Communications chart for a summary ofRS datal video communications standards. RSA See Rural Service Area. RSA An academic security research facility within the corporate structure ofRSASecurity Inc. The lab provides state-of-the-art expertise in cryptography and security technology to RSA and its customers. The lab personnel were active participants in the IEEE P 1363 project specifying standards for public key cryptographic systems. See Public-Key Cryptog- raphy Standards. RSA Security Inc. A prominent data security dis- tributor providing products that aid companies in de- veloping security/trust products and processes, especially for electronic commerce applications. The name is based upon the originators of the RSA crypto- system, Rivest, Shamir, andAdleman. See MD series, RC6. RSC 1. See remote switching center. 2. repair service center. RSFOCS See Repeatered Submarine Fiber Optic Cable Systems. RSS 1. remote switching system. 2. root sum square. Astatistical calculation that is useful in assessing er- rors such as signal distortion. RSU remote switching unit. RSVP See Reliable SAP Update Protocol RSVP Internet Reservation Protocol. An extensible, scalable protocol designed in the mid-1990s to provide efficient, robust ways to set up Internet-inte- grated service reservations, RSVP became an Inter- net standard in 1997. It has primarily been promoted by commercial interests, as it makes it possible to establish priority connections through reserved bandwidth, a feature ofinterest to large competitive busi- ness network users. RSVP is appropriate for multicast applications, although it supports unicast as well. RSVP interfaces existing routing protocols rather than performing its own routing. The RSVP is used by a host to request a specific Quality of Service (QoS) from the network. RSVP attempts to make a resource reservation for the data stream at each node through which it passes. RSVP communicates with two local decision mod- ules: admission control and policy control, to deter- mine whether the node has sufficient resources to supply the QoS, and whether the user has administrative permission to make the reservation. One of the difficulties in implementing RSVP has been assessing fees for connections across more than one network. Some opponents of the system fear the estab- lishment of"elite" Internet users based on econom- ics rather than on quality of information or services offered. RSVP development has continued since 1995 as RSVP2. See STIL RT 1. radio telephone. 2. See realtime. 3. See remote terminal. 4. reorder tone. 5. routing table. 6. See run time, runtime. RTB See regional test bed. RTC 1. realtime control. 2. runtime code. 3. runtime control. RTCA See Radio Technical Commission ofAeronau- tics. RTCP Real Time Conferencing Protocol. RTD 1. realtime display. 2. See round trip delay. RTDNA See Radio-Television News Directors As- sociation. RTDNF See Radio-Television News Directors Foun- dation. RTE remote tenninal emulation. See remote tenninal. RTF 1. See Radio Terminal Function. 2. See Rich Text Fonnat. RTFM Abbreviation for "read the freaking manual" used on public forums on the Net when a user asks a question that has been asked and answered hundreds of times and is clearly answered in the aJ?propriate documentation, or FAQ. An exhortation for the user to look it up before using up people's valuable time asking again. See Frequently Asked Question. RTL 1. Radio Television Luxemburg. News, sports, comedy, and community programming. 2. runtime license. RTM 1. realtime/runtime monitor. 2. runtime man- ager. RTML 1. See Real Time Markup Language. 2. See Remote Telescope Markup Language. 3. See Rich Text Markup Language. 4. See Robotic Telescope Markup Language. 5. See Runeberg Text Markup Language. RTOP realtime operating system. RTP 1. See Rapid Transport Protocol. 2. realtime protocol. 3. Realtime Transport Protocol. 4. See Rout- ing Table Protocol. RTTY realtime teletype. See teletypewriter. RTS 1. realtime system. 2. Request to Send. Flow control, typically used in serial communications, which is an output for DTE devices and an input for DCE devices. See TxD, RxD, CTS, DSR, DCD, DTR, RS-232. 3. remote tracking station. RTSP See Real Time Streaming Protocol. RTU 1. remote telemetry unit. A system that enables a device, such as a communications satellite in orbit, to be controlled from a remote location, such as an Earth station or space shuttle. RTUs can typically be used to orient and move the remote system by acti- vating and controlling various motors, gyros, and otherpositioning systems. The telemetry unit mayor may not have feedback capabilities. If the RTU is one- directional, then coordinates or instructions are usually sent with the hope that they will work or with the understanding that another system (such as a shuttle or telescope) will monitor the effect of the settings. If the RTU is two-directional, various types ofinformation will be relayed back to the RTU from the remote system and corrections made, if necessary. 2. remote tenninal unit. A device to activate, control, or query a system in another location. Remote termi- 827 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary Selected Overview ofRecommended Standards (RS) for Communications Designation •. ·TypelDescription RS-170 Mon.ochromeJ1deo:a standardfor analog black and white (monochrome)video adopted in North America and Japan that was prevalent until color standards became dominant. The fonnat evolved from historic broadcast specifications developed in the 19308. RS-170 carries both timing and image information on a single signal. It fonned the basis forbroadcast television for many years. The format is still widely used in monochrome security cameras where a higher-resolution picture or lower installation cost are considerations. For television, RS-170 has been superseded by RS-170a color NTSC systems and is now gradually being superseded by RS-343 and digital video formats. RS-170 broadcast standards specify 525 horizontal lines displayed as 2: 1ratio interlaced frames.·These are alternate odd- and even-line half-frames that combine perceptually to create the full frame image, generating the effect of60 frames per second. The range of the relative intensities ofindividual 'points' in the display is from no light (black) to full light ('wb.i~e'), depending upon the voltage leveLNotallof the lines are used for display; some aid in synchronization. Since there is no colorsignal (chrominance) to process and render, it is generally less expensive to manufacture m.onochrome systems. RS-170signalsaretypically transmittedthrough75-ohm well-shielded coaxial cables. Europe uses a standard similar to RS-170 called CCIR. It differs in that it supports a higher vertical resolution (625 horizontal scan lines) and operates at the rate of 25 frames per second. See NTSC, RS-170a, RS-343. RS-170a 'Analog Color Video: an Electronic Industries Association (EIA) standard for analog color video adopted in North America and Japan in 1953. Consumer RS-170a-based televisions and video editing. systems superseded RS-170 (monochrome) in the . 1970s. RS-17Oa is also gradually superseding RS-170 standards for security cameras. Eventually, RS-170a will be replaced by digital video, but it is still prevalent in composite National Television System Committee (NTSC) systems. The. original RS-170 (monochrome). format specified 525 horizontal lines for display and synchronization purposes. The RS-170a standard was intended. to· support color while being downwardly compatible with the large installed base of monochrome systems expected to reml}.ill for some time after the<color standardwasintroduced.·.There was also some consideration of video tape recorders that were becoming prevalent intheproduction and broadcast industries. RS-170a specified. 1 050 lines due to the four color fields needed for a frame throughsubcanier repeats, butthe effective resolution is compatible with RS-170, that is, 525 horizontal lines, 485 of which are displayed. RS-170 ROB refers to video signals using the red-green-blue color model (e g., many computer monitors) timed for compatibility with RS-170 specifications. SeeRS-170, RS- 343,.&8- 343a RS-232 Serial Communications. A decades-old single-ended standard for serial transmissions introduced in the early 1960s. RS-232 is widely supported on desktop computers and other devices commonly used for communicating with modems, remote terminals, and printers. R8-232 specifies the electrical and physicalcharacteristics of the connection. The most com- monbnpletpentation. isRS-23.2-C(Whichisoften transcribed as RS-23 2c. forbr~vity) and .• ~yin the industry mean RS-232cwhenthey sayRS-232. The RS-232cspecification de- finesawaytoconnectQatatermin~~quipment (DTE) with data circuit-terminating equipment(DCE). SeeRS-232 forpinollts. RS-330 Mo ll ochrome Video: an analog, monochrome composite video standard adopted in North America and Japan primarily for closed-circuit television systems. It supports a resolution of 525 horizontal lines at 60 frames per second. It is similar to RS-170 but does not require equalizing pulses. RS-250c Serial Communications: the most recent version of an analog color video standard for establishing acceptable performance in the transmission ofbroadcast-quality signals through various distances (short-, medium-, and long-haul) through a variety of wired and wireless links The 250 series was first established in the 19508. Unlike other video standards that specify resolutions, frame rates, and synchronization levels for displaying images, this one con~s itself with the delivery of a. "clean" signal· in terms of the signal-to-Iloiseratio, phase, gain, and othersignalqualitycharacteristics.Short haulRS 2S0c requirements are easier to meet now that fiber optic transmission links are available. 828 © 2003 by CRC Press LLC Designation > Type/Description RS-343/alvfonochrome Video: an analog noninterlacedmonochrome.videostandardusedf()t nonbroadcast high-resolution cameras (625 to 1023 scan lines t notallofwl1iclt(are displayed), especially security cameras for monitoring and recording purposes. Many RS- 3~3a cameras also output RS-170 for downward compatibility· Termirla ted 75-olun coaxial cables are traditionally used for transmitting the signal but RS-343aisnowalS{liSUPPorted through RS-422 and fiber optic composite and digital RBG video links for wideband. T\T, medical video, military monitoring, and computer graphics applications. RS-343a is the monochrome version - which is confusing, since RS-170 and .RS-170a are, respectively, monochrome and color. See RS-170, RS-170a. RS-328 Facsimile Communications: a standard for facsimile transmissions introduced in 1966 to help improve interopembility among facsimile equipment from different manufactures which were, at thattime, operating o~ a number of proprietary schemes .• Thiscamet~beknownas the Group 1. standard and other Group x formats have followed. Standardization has aided in implementing fax capabilities on other systems, including fax modems. See facsimile. RS-366 Parallel Di"ling: a parallel dialing standard for high bandwidth connn~cationssuchas videoconferencing RS-366·.has been subdivided into Type·I,JI t .andIII.RS.36~hasbeen· implemented on a number of types of links, including RS-449, RS-530, V.2Sbis, and V.35 modem interfaces. It is compatible with RS-232 electrical specifications and is commonly transmitted through a DB-25 connector. It has further been implemented on fiber optic modems transmitting data at speeds up to 56 Kbps per channel and is also applicable to Video transmissions over ATM networks (e g., for switched virtual circuits). There are commercial products to convert between RS-366 and Hayes AT commands. They resemble traditional modems in shape and size, with LEDs to signaLvariousindicators. These converters enable a regular asynchronous modem to be used in conjunction willian RS-366 interface. RS-422 High-speed Serial: a widely-used balanced/differential voltage twisted-pair stat1~rd for high- speed point-to~point serial transmissions~ It is backwardly compatible with RS-232 butis faster, up to ·100 Kbps, and can be transmitted over longer distancestup to about 4000 feet RS-422 can be configured to support either software or hardware handshakin~.The standard i~.nottiedtoany specific attachmentdevice contiguration, but iscomtn0nlyit1!l:demen.ted through cables with DB-9, DB-25, or 8-pin mini-DIN connectors. RS 422 is notinherently a multidrop standard, but 4-wire, half-duplex links can be constructed to·providesome of the benefits associated with multidrop formats such as RS-485 •. See RS-485 .• See differential cable, RS-232. RS-423 High-speed Serial: abalanced/differential voltage twisted-pair serial transmissions standard backwardly compatible with RS-232, butwith multidrop capabilities and transmission distances ofup to 4000 feet Compared to RS0232 and RS-422, this standard has notbeen widely implemented. RS-449 High-Speed Serial: a balanced/differential voltage twisted-pair standard for high-speed synchronous data transmissions. The signaling is associated with speci~c pin assignments for DB-9 and DB-37 connectors. This has been superseded by RS-530.See RS-232,RS-530~ RS-48S High-Speed Serial: a widely used balanced/differential voltage pair standard, downwardly compatible with RS-422, for high-speed serial transmissions, up to 100Kbps.\It has become p~Pt1lar in.industrialand telecommunicationsapplicationsforc0nt1e~tingm~~~ple peripherals·(printers, industrialfabricators, etc.) through multidroptransceivers/transrrHtters. Up to 64 devices may be connected, 32 for each multidrop line. RS-485 supports drivers with higher voltage output ranges than RS-422. It can be used in half-duplex or full-duplex mode, but is commonly implemented asbalf-dup1ex. RS-48Smay or may not need to be tenninated, depending upon the configuration. As with.RS-422, the fonnat is not tied to any particular type of connector. See differential cable, RS-422, RS-232. RS-530 High-SpeedSerial: a balanced/differential voltage twisted-pair standard for high-speed serial transmissions that supports RS-422IRS-423 and the oldie-but-prevalent RS-232. It is specified for a DB-25 connector. There are commercial devices to convert between RS-530 and the older RS-232 serial fonnat that. is still supported on many computers There are also cables to convert between RS-530 and\To3S, X.21, and RS-449/RS-442 formats. RS-530can be supported over high-speed, point-to-point fiber optic modem links for distances of up to 30 km. Thus, a system with an RS-530 interface can connectthrough t\visted-l'air cable to a fiber optic.modem,\Vhichthen.transmits. to~nother~Ber()p~ic J1194em and twisted-pair at the other end of the fiber link. RS-S30supersedesRS-449.· 829 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary nal units range from simple to sophisticated but, in general, refer to a remote terminal earmarked for a particular purpose, such as testing and diagnostics in a network system. A small-scale remote terminal is similar in concept to a televisionNCR remote control but usually provides more control and better processing capabilities than typical remote controls. Older computers are often used as remote terminal units to control security systems and home automa- tion systems (heat, lights, etc.). RTV realtime video. Video that appears as natural movement, usually with at least 20 frames per second, and which further may be a live broadcast as opposed to playback from stored information. On the Inter- net, a technology called streaming video is becoming popular for airing live newscasts. In the past, most animations were developed, compressed, and stored in an Internet-accessible location for the user to down- load and play back on his or her local system. Stream- ing video enables the user to link into a live data stream and watch the action as it happens. RU 1. In packet networking request unit, response unit, request/response unit. See basic information unit. 2. receive/receiving unit. RU A Remote User Agent. Asoftware agent that acts on behalfofa client making a request or supplying information from a remote terminal. See User Agent. rubber bandwidthjargon Acommunications channel whose bandwidth can be dynamically altered, that is, it can be changed without terminating and reinit- iating the transmission. This colorful phrase appar- ently originates from Ascend Communications, a supplier ofnetworking-related products, to describe characteristics of an inverse multiplexing system. Ruhmkorff coil An induction coil used to induce high voltages, first constructed in the mid-1800s by Eugene Ducretet, though the instrument is associated with Heinrich Ruhmkorff. This technology was developed into ignition coils. See coil, induction. Ruhmkorff, Heinrich Daniel (1803-1877) A Ger- man physicist of the 1800s who constructed and distributed the induction spark coil, following pioneer work by Nicholas Callan and Charles Grafton Page and practical embodiments by Eugene Ducretet. ruled gratingAplanar grating structure for controlling light passage in the optical frequencies. It is cre- ated mechanically by machining fine, parallel grooves into a surface supported by a substrated. Standard gratings are available for controlling specific wavelengths and other wavelengths can be re- quested as custom fabrications. Ruled gratings are typically described in terms of the number of grooves per millimeter, the blaze angle, and the optimal wavelength to which it is "tuned." Ruled gratings tend to be favored for less precise applications and less dense grating patterns where stray light is less apt to interfere with overall efficiency and where efficiency in the optical spectrum is desired. A blazed grating is one in which the rules are slightly asymmetric. See blaze angle, interference grating. rumbatronA term used by William Hansen for pioneer cavity resonating devices in the 1930s. The term 830 was subsequently adopted by Russell Varian, in collaboration with Hansen, to describe a Rumbatron Oscillator, the germinal idea for the Klystron tube. [The author was not able to find afirsthand reference as to whether Hansen spelled it rumbatron or rhumbatron. For consistency with Varian's Rum- batron Oscillator, it is spelled without the "h."] See Klystron. run v. To initiate and execute asoftware program, or linked suite of programs which form an application. run length encoding RLE. Alossless data compression technique that works well with data that include repeated sequences. The repeated sequences (white spaces in a document, a single background color in an image, etc.) are replaced with a code that indicates that what follows is astring of the same character of a particular length. If run length encoding is used on data with little or no redundancy, the encoded file may be longer than the original. Rundgren, Todd (1948- ) A multimedia recording artist who has managed to stay at the forefront of emerging interactive entertainment technologies, syn- thesizing the new capabilities in media into video and sound. Rundgren began programming microcomput- ers in the late 1970s, adapting Macintoshes, Amiga Video Toasters, and other systems to many new creative venues, producing new types of music albums, computer-generated rock videos, and interactive TV entertainment concerts. Since the mid-1990s, Rundgren has been president/CEO of Waking Dreams, which develops, licenses, and distributes products and services originating from creative and undervalued ideas. run time The time during which a software routine or application executes. This can easily be confused with "runtime" which refers to CPU cycles and computer processing time. In contrast, run time is the overall length of time ajob might take from submis- sion to completion. Thus, a database query might take 5 minutes of run time or execution time to provide a result, yet require only 3 seconds of CPU runtime to execute. To confuse matters further, many people use these terms interchangeably and run time licenses are often spelled "runtime." See runtime. run time license A onetime, per-use, or other distribution license granted by a software developer to al- low a vendor to include the licensor's algorithms, usually for inclusion in an enduser product (often called a"customer application"). runtime In computer processing terms, this is the duration, that is, the CPU time (usually expressed in cycles), used to execute aroutine or program. A process that takes 5 minutes for the user might require only 3 seconds of CPU runtime because computer time is often spent pondering or waiting for peripherals. Runtime is a reasonably objective value with comparative benefits for optimizing software algorithms and practical billing applications for shared access systems. See run time. rural automatic exchange RAX. An automatic telephone exchange that didn't require a human operator to patch the connections, intended for rural commu- © 2003 by CRC Press LLC nities. Siemens is credited with installing the first 40- line RAX in the U.K. in 1921. Radio-equipped, so- lar-powered RAX systems were introduced to rural areas in India in 1985. Rural Local Broadcast Signals Act H.R. 3615. An act passed by the U.S. House ofRepresentatives in April 2000 that extends loan guarantees to companies providing local television broadcasting through satellite transmissions. H.R. 3615 amends the Rural Electrification Act of 1936 to ensure access to TV broadcasting by multichannel video providers to all households in underserved areas that desire the service by December 31, 2006. The Act was felt to be important because weather, emergency, and other crucial information was often disseminated through broadcast television, in addition to educational and entertainment programming. Other services, such as Internet access, may also be offered. Satellite access also serves as a competitive alternative for rural consumers. The Act will serve to improve access to more than 6 million satellite dish owners in rural areas. However, that still leaves the other 50% unserved and in need ofsupport in having access to the same programming as urban subscrib- ers. The Act was placed on the Senate calendar in May 2000. See Local TV Act of2000. RuralLocal Television SignalsAct U.S. regulations adopted in 1999 as part of the Satellite Home Viewer Improvement Act (SHVIA) for delivering local broadcast television signals to satellite television sub- scribers in unserved and underserved local television markets, a spectrum that would otherwise be allocated to commercial use. There was controversy regarding this issue and whether the terms of SHVIA suffi- ciently addressed the problem of rural access. These discussions lead to the Rural Local Broadcast Sig- nals Act and the LOCAL TV Act of 2000. See Rural Local Broadcast Signals Act, LOCAL TV Act of2000. Rural Service Area RSA. An administrative designation used by many commercial and public service organizations, including telecommunications providers and public libraries. For telephone service, regions not defined as Metropolitan Service Areas (MSA) are in the category of Rural Service Area, which includes smaller cities (usually under about 50,000 inhabit- ants), towns, and rural regions. The Federal Commu- nications Commission has recognized over 300 MSAs and over 400 RSAs in the U.S. and has further used this designation to license non-MSA cellu- lar carriers. Libraries use a similar categorization to define their public service regions as urban, suburban, and rural service areas. The rural service area is often defined as those areas outside the urban and suburban bound- aries or may be defined in terms of its radius distance from the library facility, depending upon the geo- graphical characteristics of the region. Since telecommunications services are typically contained within a fixed building setting, the designation ofRSA is an important one because library services such as Inter- net access may need to be provided in some mobile form (similar to aBookmobile service). Providers serving RSAs have many unique problems with installing and maintaining profitable enterprises. Rural areas have smaller population-to-Iand ratios that necessitate more wires for fewer people and longer trips for service personnel. Rural areas often require a larger proportion of long-distance services compared to local services. To complicate matters further, the topography ofrural areas may be rough and inaccessible, especially in mountainous regions. Even rodents pose a problem in rural areas, chewing through communications wires installed above- ground on rocky terrain. In terms of fast Internet access, ISDN and other services are disproportionately skewed toward Metropolitan Service Areas. Wireless communications might seem to be an ideal solution to many of these problems, but RSA providers often are smaller organizations that have difficulty com- peting with larger finns for Federal Communications Commission (FCC) licenses for wireless services. ruraltelephone company This is defined in the Tele- communications Act of 1996 and published by the Federal Communications Commission (FCC) as: " a local exchange carrier operating entity to the extent that such entity- (A) provides common carrier service to any local exchange carrier study area that does not include either- (i) any incorporated place of 10,000 in- habitants or more, or any part thereof, based on the most recently available population statistics of the Bureau of the Census; or (ii) any territory, incorporated or unin- ~!~:~~~l~~:H~~~}~}~~~ • (B) provides telephone exchange service, including exchange access, to fewer than 50,000 access lines; (C) provides telephone exchange service to any local exchange carrier study area with fewer than 100,000 access lines; or (D) has less than 15 percent of its access lines in communities of more than 50,000 on the date ofenactment of the Telecommunica- tions Act of 1996." See Federal Communications Commission, Telecom- munications Act of 1996. Rural Utilities Service RUS. A U.S. Department of Agriculture agency that provides technical and fund- ing support for rural utilities infrastructure projects involving electricity, water, and telecommunications. http://www.rurdev. usda.gov/rus/ RURL Relative Uniform Resource Locator, Relative URL. A compact representation of the location and method of access for a resource accessible over the Internet that is described relative to an absolute base URL. In contrast, an absolute base URL is one for which a specific location is established, such as http://www.4-sights.com/and remains the same no matter where the Web page holding the link, for 831 © 2003 by CRC Press LLC . com- monbnpletpentation. isRS-23.2-C(Whichisoften transcribed as RS-23 2c. forbr~vity) and .• ~yin the industry mean RS-232cwhenthey sayRS-232. The RS-232cspecification de- finesawaytoconnectQatatermin~~quipment (DTE) with data circuit-terminating equipment(DCE). SeeRS-232 forpinollts. RS-330 Mo ll ochrome Video: an analog, monochrome composite video standard adopted in North America. for high-speed serial transmissions that supports RS-422IRS-423 and the oldie-but-prevalent RS-232. It is specified for a DB-25 connector. There are commercial devices to convert between RS-530 and the older RS-232 serial. optic.modem,Vhichthen.transmits. to~nother~Ber()p~ic J1194em and twisted-pair at the other end of the fiber link. RS-S30supersedesRS-449.· 829 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary nal units range from simple to sophisticated but, in general,

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