Fiber Optics Illustrated Dictionary - Part 84 doc

The to-ken 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, • telemark

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 of light as II

min-utes 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 theAstronomer Royalat the Danish

court of ChristianV

!Wmer invented a new type of thermometer and

com-municated some of his ideas to D Fahrenheit in the

early 1700s.InDenmark, he introduced a new

sys-tem for numbers and weights that combined the

con-cepts 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

de-veloped the first widely known telegraph systems

Ronalds also experimented with other types of

tele-graph systems Charles Wheatstone corresponded

with Francis Ronalds around the time he developed

a telegraph withw.F.Cooke The British Navy failed

to adapt Ronalds' telegraph system, choosing instead

to continue their "tried and true" semaphore system

ofsignaling See Schilling, Pavel Lvovitch; Morrison,

Charles; Wheatstone, Charles

Ronchi grating Aseries ofperfectly straight lines

im-pressed into glass, acrylic, or other film surface It is

a specific type of diffraction grating in which the

dis-tance between the grating facets and the facets

them-selves are the same When placed near the focal point

of an incident beam oflight, imperfections in the

op-tical 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 ofthe results to reference ideals See

dif-fraction grating, Ronchi test, Ronchigram, star test

See knife-edge focusing

Ronchi test Away to test the optical quality of a

tra-ditional lens such as a telescopic mirror lens by

us-ing a Ronchi gratus-ing, with evenly spaced, straight

lines as a reference against which aberrations in the

optical system can be seen.Ingeneral, the tester is

placed at the center of the point of curvature ofa

mir-ror, 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

Itis 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 para-bolic 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 orien-tation 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

~)I(e~I~(I)

A Ronchigram is a reference imagefor 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-ented flat in relation to the plane of the Ronchi grat-ing This isfairly easy to visualize and intuitively com-pare The other images can indicate aberrantpatterns for a supposedly regular mirrored slllface or they can serve as references for other shapes, such as pQl'abo-laid mirrors which are not as easy to intuitively check For nonflat surfaces the distance from 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 pos-sible to carry out a Ronchi test on a basic flat mirror without Ronchigrams, because aberrations will mani-fest as curved lines or fuzzy areas that can be readily seen, but when testing parabolic or other nonflat sur-faces, there are more variables to control and the dis-tance from the mirror, its orientation, and its shape may change the test results to manifest as a wide va-riety of patterns that can't always be intuitively as-sessed without a reference image Computer software can be used to predict the Ronchi pattern, at a given distance, for a reflective surface ofa given shape See Foucault test, Ronchi grating, Ronchi test

Rontgen, Wilhelm Konrad (1845-1923) AGerman physicist and educator who developed the vacuum tube (1895), the fluoroscope, and pioneer experimental

and medical radiology He was the first recipient of

the Nobel prize in physics The roentgen unit of

X-radiation is named after him See roentgen, X-rays

root mean square (abbrev.rms) The effective value

of a quantity in a periodic circuit, measured through

the duration of one period

root name serverOn distributed computer networks,

name servers provide a means to administer the

trans-mission and routing of data among source and

desti-nation computers Name servers are a type ofaddress

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

serv-ers and TLD servserv-ers, it was proposed in the

mid-1990s that a distinction be made between the two

groups as the performance needs ofroot servers were

felt to be greater than for many other types of

serv-ers It was further proposed that requirements be

for-mally laid down for root name servers so that

ven-dors and implementors would have appropriate tools

for handling the more stringent requirements of root

name servers See Domain Name Server, RFC 2010

ROSATRBntgen 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

ROSESee Remote Operations Service Element

Rosenbliith, ArturoAphysiologist who collaborated

with Norbert Wiener in investigations in artificial

in-telligence and self-organizing systems, much of

which was documented in Wiener's book on

cyber-netics

Ross testSee Dall test

rotary dialIntelephony, a circular dial mechanism

typically activated by placing a finger (or pencil end)

in one of a series of punched out holes, and turning

(dialing) The mechanism springs back to its

origi-nal 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

dial-ing signals Rotary phones are steadily bedial-ing

super-seded by pushbutton phones See pulse dialing, tone

dialing, keypad, touchtone phone

rotary huntA 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

rotary switchAcommercially 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-vision in 1925 See Lorimer switch, panel switch, rotary switch

ROTLRemote Office Test Line A means of auto-matically 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 Ascheduling or resource-alloca-tion system that "divvies up" tasks or resources more

or less equally among all the participants in a gener-ally 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.Ingeneral, 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 ofthousands ofyears) for scheduling work and play and for providing fair ac-cess to resources on a rotating basis

The Round Robin system, as we now understand it,

is at the heart ofmany scheduling algorithms that use the same general cyclic event-driven concept Round Robin systemsareused to allocate computers, modems, printers, and many other heavily accessed systems

~i~;r;i~::;i~~~~~;r~~~~I~~~:1f~:~ i. ofpeople or multiple Round Robins intended to take

place concurrently Other common Round Robin ap-plications include

• token passing in a Token-Ring network The to-ken 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, es-pecially in situations where the agent is earning

a commission and wants a fair share ofthe calls, and

computer operating systems running multiple processes in which the computer moves on to the next process ifthe previous process has com-pleted, 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 ofdifferent participants or pro-cessing systems For example, in a telemarketing firm, ifthere is a crackerjack sales representative with seniority who always closes a sale, the Round Robin system ofassigning incoming calls might be weighted

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 Aload-balancing

resource-shar-ing system implemented on the Internet through

re-cent version DNS/BIND 4.9 (Domain Name System

with BIND) that arose in part because of heavy

ac-cess to favored sites on the World Wide Web This

enables a cluster ofservers 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 ofhandling server failures, as the Round Robin

system is inherently intolerant ofmissing 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

in-stalling, configuring, and tuning networks Some

de-lays are evaluated in relation to what the elapsed time

should theoretically be and some are evaluated

rela-tive to a test suite ofalternate 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 of light 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.Anopen

distance-vec-tor routing protocol for distributing routing

informa-tion through Internet-connected systems ranging from

large Internet Service Provider (ISP) systems to

lo-cal area networks (LANs) The protocol was

submit-ted asanRFCbyR.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,itmay also be

used on User Datagram Protocol (UDP) port 38 RAP

propagates routes opposite to the direction ofthe path

of the datagrams using the associated routes Source

restriction may be invoked to provide a certain mea-sure of security and must be added to routesifsecurity 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 diversityAnarchitecture providing a number ofoptions 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 (usu-ally from losing one or more nodes) exceed the ca-pacity 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 ex-ceed the number of routing paths expected to be needed to prevent this serious problem

router 1 Adevice 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, dependinRupon the degree of

auto-mation and "intelligence' built into the router There used to be somewhat of a distinction between rout-ers and switches, but switches are becoming so so-phisticated 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 con-tribute significant network management functions, such as priority and load balancing They can be pro-tocol-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 receiv-ing frame relay frames, and strippreceiv-ing the frame relay frame to restore the information to its original form, passing it on to the end device With improved tech-nologies, the distinction between routers and bridges

is lessening Even switches now have many ofthe ca-pabilities of routers See bridge, gateway, switch routing Selecting or establishing a path.In telecom-munications, the path may be used to transmit super-visory signals and data (either together, separately,

or over separate paths) Routing may be static or dy-namic 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

routing aggregationAnadministrative tool for

or-ganizing and optimizing the use and availability of

routes to deal with the continually rising demand on

networks Users are encouraged to return unused

ad-dresses, and old addresses are assigned prefixes so

multiple routes can be aggregated into one

Routing Arbiter DatabaseRADB A routing

data-base established by the Routing Arbiter project One

of several databases in the Internet Routing Registry

Routing Arbiter ProjectA National Science

Foun-dation-funded project given the task of coordinating

routing for the new NSFNet architecture in

coopera-tion with a number of educacoopera-tional 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 ofthe ZIP+4 code 3 In networks, the data

parsed by the router or switcher to establish a path 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 domainRD In ATM networking, a

collec-tion ofsystems that have been grouped topologically

within one routing system

routing information baseRIB A static or dynamic

table ofrouting paths maintained within a router 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 ProtocolRIP Avery common

routing protocol from a family of protocols known

as the Interior Gateway Protocols (IGPs) RIP

evalu-ates the path between two points in terms ofhops

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.Inorder 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 ServersSpecialized servers from the Routing

Arbiter project intended to hold clearinghouse

rout-ing information in a Routrout-ing Infonnation Base at each

network interconnection point in order to eliminate,

ers are not intended to actually transmit the traffic, but serve to handle the flow of information concern-ing pathways

routing table, data networkIn data networks, a table detailing paths to specific Internet Protocol (IP) ad-dresses With the explosive growth of the Net, the number ofpaths, and hence the size ofthe 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 ofrouting paths, with provider-based routing being favored due to greater ease of implementation, and geographic-based routing proposed because it has less of a tendency to con-centrate power in the hands ofa few large providers routing table, telephone networkIn telephone communications, routing tables serve to record and provide information for the processing of incoming calls Thus, calls may not just go to a particular caller

or workstation, they may be directed to automated voice services, voicemail, queued holds, recordings, etc They may require the capability ofstepping back through the route as well, depending upon the sophis-tication of the system and the selections available to the user

Routing Table Maintenance ProtocolAnAppleTalk network routing protocol that is based upon Internet Protocol (IP) Routing Information Protocol RTMP

is a transport-layer protocol that manages routing in-formation within an AppleTalk router and facilitates the exchange of routing 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 ofthe desti-nation network See Routing Information Protocol Routing Table ProtocolRTP A network communi-cations 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 ofnet-work topology information among the various serv-ers and enables servserv-ers and routserv-ers to identify othserv-ers nearby It works in conjunction with other protocols such as the Address Resolution Protocol (ARP) See Routing Information Protocol

routing updateNetwork configuration information provided by a router and, in some cases, costs asso-ciated with use ofparticular routes Routing updates can be scheduled to be automatically sent out at speci-fied intervals, and are typically broadcast if signifi-cant network configuration changes have been made row1 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, ofmore or less horizontally aligned elements arranged within a grid or tabular format This mean-ing of the word is commonly used to describe screen

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 cablewithsuitable 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 ter-minals, 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-ter-minating 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 D connec-tors are sometimes used (or 25-pin connecconnec-tors with some ofthe pins unconnected) Afew systems specify more than 11 or 12 pins (pin 12 is not part ofthe 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 im-portant 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 SocietyAnindependent national academy of

science, founded in 1660 to support the British

sci-entific community The Society funds research,

stimulates international communication among

sci-entists, hosts conferences, produces reports

andjour-nals, and maintains one of the most remarkable

his-toric archives ofscientific endeavor in the world

dat-ing back to 1470 (which includes records and photos

ofmany ofthe major advances in computing and

tele-communications) Among its publications is the

Philosophical Transactions of the Royal Society

which was first printed in 1665 The society has

rec-ognized 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

ra-dio 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 Acomputer

pro-gramming language for processing and displaying

large data files 2 See role-playing game

RPM Remote Packet Module

RPN reverse Polish notation A mathematical

nota-tion 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

com-monly 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

RPOASee Recognized Private Operating Agency

RPOPRemote Post Office Protocol See Post Office

Protocol

RPS See repetitive pattern suppression

RPTrepeat

RPVSee remotely piloted vehicle

RQSSee Rate Quote System

RR 1 radio regulation 2 railroad 3 return rate

4 See Round Robin 5 rural route

RRSFRACF remote sharing facility See remote

access control facility

RS1 radio satellite 2 recommended standard See

RS-232 for an example using this prefix 3 remote

station 4 reset 5 See Royal Society

RS-lAlong with RS-2, the first USSR amateur

sat-ellites, launched in October 1978

RS-232Recommended Standard 232 Adecades-old

single-ended standard for serial transmissions

intro-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)

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

RSASee Rural Service Area

RSAAn academic security research facility within

the corporate structure ofRSA Security 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 P1363 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,

espe-cially for electronic commerce applications The

name is based upon the originators ofthe RSA

crypto-system, Rivest, Shamir, andAdleman See MD series,

RC6

RSC1 See remote switching center 2 repair

ser-vice center

RSFOCSSee Repeatered Submarine Fiber Optic

Cable Systems

RSS1 remote switching system 2 root sum square

A statistical calculation that is useful in assessing

er-rors such as signal distortion

RSUremote switching unit

RSVPSee Reliable SAP Update Protocol

RSVPInternet Reservation Protocol An extensible,

scalable protocol designed in the mid-1990s to

pro-vide 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

band-width, a feature ofinterest to large competitive

busi-ness network users

RSVP is appropriate for multicast applications,

al-though 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 ofService (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

adminis-trative permission to make the reservation One ofthe

difficulties in implementing RSVP has been

assess-ing fees for connections across more than one

net-work 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

terminal 4 reorder tone 5 routing table 6 See run time, runtime

RTBSee regional test bed

RTC 1 realtime control 2 runtime code 3 runtime control

RTCASee Radio Technical Commission ofAeronau-tics

RTCPReal Time Conferencing Protocol

RTD 1.realtime display 2 See round trip delay RTDNASee Radio-Television News Directors As-sociation

RTDNFSee Radio-Television News Directors Foun-dation

RTEremote tenninal emulation See remote tenninal RTF1 See Radio Terminal Function 2 See Rich Text Fonnat

RTFMAbbreviation 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 beforeusing 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

RTM1 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

RTOPrealtime operating system

RTP 1 See Rapid Transport Protocol 2 realtime protocol 3 Realtime Transport Protocol 4 See Rout-ing Table Protocol

RTTYrealtime 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

RTU1 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 other positioning systems The telemetry unit mayor may not have feedback capabilities IftheRTUis 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 of infor-mation will be relayed back to the RTU from the re-mote system and corrections made, if necessary

2 remote tenninal unit A device to activate, control,

or query a system in another location Remote

termi-Fiber Optics Illustrated Dictionary

Selected Overview of Recommended Standards(RS)forCommunications Designation •.·TypelDescription

RS-170 Mon.ochromeJ1deo:astandardfor analog black and white (monochrome)video adoptedin

North America and Japan that was prevalent until colorstandardsbecame dominant The fonnat evolved from historic broadcast specifications developed in the 19308.RS-170carries both timing and image information on a single signal It fonned the basisforbroadcast television for many years The format isstill widelyused 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 colorNTSC systems andis now graduallybeing supersededbyRS-343and digitalvideoformats

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 perceptuallyto

create the full frame image, generating the effect of60 frames per second The range of the relative intensities of individual 'points'inthe display is from no light (black) tofulllight

('wb.i~e'),depending upon the voltageleveL Notall of the lines are used for display; some aid

insynchronization 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 usesastandard similartoRS-170calledCCIR Itdiffers in that it supports a higher vertical resolution(625horizontal scan lines) and operates at the rate of25frames per second See NTSC, RS-170a, RS-343

RS-170a 'Analog Color Video:anElectronic Industries Association(EIA)standard for analog color

video adoptedinNorth America and Japanin1953 Consumer RS-170a-based televisions and video editing systems superseded RS-170 (monochrome)inthe 1970s RS-17Oaisalso gradually superseding RS-170 standards for security cameras Eventually, RS-170a will be replacedbydigital video, but it is still prevalent in composite National Television System Committee(NTSC)systems

The originalRS-170(monochrome) format specified525horizontallinesfor display and synchronization purposes The RS-170a standardwasintended.to·support color while being downwardly compatible with the large installed base ofmonochrome systems expected to reml}.ill for some time after the<color standardwasintroduced.·.There was also some

consideration of video tape recorders thatwerebecoming prevalent intheproduction and broadcastindustries RS-170a specified.1050 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 ofwhich 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 170 specifications See170, RS-343,.&8-343a

RS-232 Serial Communications A decades-old single-ended standard for serial transmissions

in-troduced intheearly 1960s RS-232is widely supported on desktop computers and other devicescommonlyused for communicating with modems, remote terminals,and printers R8-232specifies theelectricalandphysical characteristicsoftheconnection.Themost

com-monbnpletpentation.isRS-23.2-C(Whichisoftentranscribedas RS-232c.forbr~vity)and .•~yinthe industry mean RS-232cwhenthey sayRS-232 The RS-232cspecification

de-finesawaytoconnectQatatermin~~quipment (DTE) with data circuit-terminating equip-ment(DCE) SeeRS-232 forpinollts.

RS-330 Mo ll ochrome Video:ananalog, monochrome composite video standard adoptedinNorth

America and Japanprimarilyfor closed-circuit television systems It supports a resolutionof

525 horizontal lines at 60framesper second It is similar toRS-170 butdoes notrequire equalizing pulses

RS-250c Serial Communications:the most recent version of an analog color video standard for

establishing acceptable performanceinthe transmission of broadcast-quality signals through various distances (short-, medium-, and long-haul) through a variety of wired and wireless links The 250 series wasfirstestablished in the 19508 Unlike other videostandardsthat specify resolutions,framerates, and synchronization levels for displaying images, this one

con~sitselfwith the delivery of a."clean" signal· in terms of the signal-to-Iloiseratio, phase, gain, and other signalqualitycharacteristics.Short haulRS 2S0c requirementsare easier to meet now that fiber optic transmission links are available

RS-343/alvfonochrome Video: an analog noninterlacedmonochrome.videostandardusedf()t

nonbroadcast high-resolution cameras (625 to 1023 scan linestnotallofwl1iclt(are

displayed), especially security cameras for monitoring and recording purposes Many

RS-3~3acameras also output RS-170 fordownwardcompatibility·Termirlated 75-oluncoaxial 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 introducedin1966 to help

improve interopembility among facsimile equipment from different manufactures which were, atthat time, operatingo~a number of proprietary schemes.•Thiscamet~beknownas

theGroup1 standard and other Groupxformats have followed Standardizationhasaidedin implementing fax capabilities on other systems, including fax modems See facsimile

RS-366 Parallel Di"ling: a parallel dialing standard forhighbandwidthconnn~cationssuchas

videoconferencing RS-366·.has been subdivided into Type·I,JIt.andIII.RS.36~hasbeen·

implemented on a number of types oflinks, including RS-449, RS-530, V.2Sbis, and V.35 modem interfaces.Itis compatible with RS-232 electrical specifications and is commonly transmitted through a DB-25 connector.It has further been implementedonfiber optic

modems transmittingdataat speeds up to56Kbps per channel and is also applicable to Video transmissions overATM networks (e g., for switched virtual circuits)

There are commercial products to convert between RS-366 and HayesATcommands They resemble traditional modems in shape and size, with LEDs to signaLvariousindicators These converters enable a regular asynchronousmodem to be usedinconjunction willianRS-366 interface

RS-422 High-speed Serial: a widely-used balanced/differential voltage twisted-pairstat1~rdfor

high-speedpoint-to~point serialtransmissions~ It is backwardly compatible with RS-232 butis faster, up to ·100 Kbps, and can be transmitted over longer distancestup to about 4000feet RS-422 can be configured to support either software or hardwarehandshakin~.The standard

i~.nottiedtoany specific attachmentdevicecontiguration, but iscomtn0nlyit1!l:demen.ted through cables with DB-9, DB-25, or8-pinmini-DIN connectors RS 422 is not inherentlya multidrop standard, but 4-wire, half-duplex links can be constructed to·providesome ofthe 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 transmissionsstandard

backwardly compatible with RS-232, butwithmultidrop 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 signalingisassociated withspeci~cpinassignments for DB-9 and DB-37 connectors This has been supersededbyRS-530.SeeRS-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 100 Kbps.\It has become

p~Pt1larin.industrialandtelecommunicationsapplicationsforc0nt1e~tingm~~~ple

peripherals· (printers, industrialfabricators, etc.) through multidroptransceivers/transrrHtters

Up to64devices may be connected, 32 for each multidrop line

RS-485 supports drivers with higher voltage output ranges than RS-422 It can be usedin 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.Aswith.RS-422, the fonnatisnot tied to any particulartypeof connector.Seedifferential cable, RS-422, RS-232 RS-530 High-Speed Serial:a balanced/differential voltage twisted-pairstandard forhigh-speedserial

transmissions that supports RS-422IRS-423 and the oldie-but-prevalent RS-232 It is

specified for a DB-25 connector There are commercial devicestoconvert 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 ofupto 30 km Thus, a system with an RS-530 interface can connect through

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.·

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

con-trol but usually provides more concon-trol and better

pro-cessing 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 calledstreaming videois

becom-ing popular for airbecom-ing live newscasts.Inthe 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

RUA Remote User Agent Asoftware agent that acts

on behalf of a client making a request or supplying

information from a remote terminal See User Agent

rubber bandwidthjargonAcommunications

chan-nel 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 of networking-related products, to describe

characteristics of an inverse multiplexing system

Ruhmkorff coilAninduction 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

de-veloped into ignition coils See coil, induction

Ruhmkorff, Heinrich Daniel(1803-1877) A

Ger-man physicist ofthe 1800s who constructed and

dis-tributed 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

control-ling 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

spe-cific wavelengths and other wavelengths can be

re-quested as custom fabrications

Ruled gratings are typically described in terms ofthe

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

ap-plications 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

rumbatronAterm used by William Hansen for

pio-neer cavity resonating devices in the 1930s The term

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 a firsthand 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

runv To initiate and execute a software program, or linked suite ofprograms which form an application run length encodingRLE A lossless data compres-sion 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 a string 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

belongerthan 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 cre-ative venues, producing new types ofmusic albums, computer-generated rock videos, and interactiveTV 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 timeThe time during which a software routine

or application executes This can easily be confused with "runtime" which refers to CPU cycles and com-puter 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 ofrun timeorexecution timeto provide a result, yet require only 3 seconds of CPUruntimeto execute To confuse matters further, many people use these terms interchangeably and run time licenses are often spelled "runtime." See runtime

run time licenseA onetime, per-use, or other distri-bution 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")

runtimeIn computer processing terms, this is the duration, that is, theCPUtime (usually expressed in cycles), used to execute a routine or program.A pro-cess 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 periph-erals Runtime is a reasonably objective value with comparative benefits for optimizing software algo-rithms and practical billing applications for shared ac-cess systems See run time

rural automatic exchangeRAX.Anautomatic tele-phone exchange that didn't require a human operator

to patch the connections, intended for rural

commu-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 of Representatives in

April 2000 that extends loan guarantees to

compa-nies 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

ser-vice 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

addi-tion to educaaddi-tional 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

Rural Local Television Signals Act U.S regulations

adopted in 1999 as part ofthe 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.Anadministrative

desig-nation used by many commercial and public service

organizations, including telecommunications

provid-ers and public libraries For telephone service, regions

not defined as Metropolitan Service Areas (MSA) are

in the category ofRural 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

fur-ther 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 ofits radius distance

from the library facility, depending upon the

geo-graphical characteristics ofthe region Since

telecom-munications 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 a Bookmobile service)

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 of rural 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 ac-cess, 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 rural telephone 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 lo-cal 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 ofthe Bureau of the Census; or

(ii) any territory, incorporated or

(B) provides telephone exchange service, in-cluding 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 ofmore than 50,000 on the date of enactment 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/andremains the same no matter where the Web page holding the link, for