Fiber Optics Illustrated Dictionary - Part 68 ppt

MIDI is a standard protocol for communication of sound information through a number of specified param-eters.. Fiber Optics Illustrated Dictionarydifferent means of delivering programmin

Fiber Optics Illustrated Dictionary

Josef Murgas - Telegraphy Pioneer

Josef Murgas, pastor of the Sacred Heart Church [Photo portrait courtesy of the /t)Joming Historical and Geological Society copyright expired by date.}

Museum of Radio and Technology A nonprofit, volunteer-assisted antique radio technology museum, located in a converted elementary school in Hunting-ton, West Virginia.It includes crystal radio sets, vacuum tube technologies, schematics, vintage books and magazines, and other educational resources and exhibits

Museum of Television and Radio Anonprofit, New York-based preservation and education institution es-tablished in 1975 by William S Paley Its goal is to collect and preserve historic radio and television pro-grams and make them available for public education and use.In1991, it was moved to the William S Paley building It houses over 60,000 programs selected for

OJ

I'J:f/.4.

I

'~';"J~

A "quenched spark" device from one of Joseph Murgas' patents /i'Om 1911 [U.s patent diagram,

public domain.}

I'

"a

inquisitive and set up a laboratory in the attic for

ex-periments Over the years, he received numerous

pat-ents for his devices; he transferred these to a

syndi-cate called the Universal Aether Telegraph Company

In 1904, Murgas patented a tone system of wireless

telegraphy with a rotary spark for transmitting faster

than the traditional Morse code system He then built

a high transmitting tower which was hailed in the

lo-cal newspaper as the "World's First Telegraphy

Tower." Many prominent citizens witnessed a test

demonstration in September 1905 and a public

dem-onstration in November 1905, after which Murgas

traveled to New York to meet with Guglielmo

Mar-coni and Reginald Fessenden Unfortunately, gale

force winds destroyed Murgas' transmitting tower

and other bad luck befell him soon after He was

get-ting on in years and having financial difficulties, so

he sold his important invention to Guglielmo

Mar-coni, to prevent his discoveries from being lost to

humanity

Murgas' achievements have not gone entirely

unrec-ognized President Calvin Coolidge honored him by

appointing him to the National Radio Commission

Liberty ship #2881 was named after him during

World War II A U.S Senate Bill adopted I October

1985 urged the Citizen Stamp Advisory Committee

of the U.S.P.S to issued a commemorative stamp of

Father Murgas to celebrate Slovak Heritage Month

See Marconi, Guglielmo

Murphy's law Reportedly stated by Edward A

Murphy as "Ifthere are two or more ways to do

some-thing, and one ofthose can result in catastrophe, then

someone will do it." and also reported as "Ifthere is

any way to do it wrong, he will." However it was

originally worded, Murphy's apropos observation

was quoted a few days later, in a news conference,

by Dr John Stapp, a surgeon and research subject in

studies ofhuman tolerance to high-velocity ejections

and gravity forces (Gs) The statement is often

re-stated more simply as "If something can go wrong,

it will." See Murphy, Edward

Murphy, Edward A An American engineer

in-volved in human testing of some spectacular

ac-celeration/deceleration experiments in the U.S Air

Force in the 1950s Following his observations about

the configuration of sensors, he is best known for a

prescient observation about catastrophes now known

as Murphy's law See Murphy's law

Murray loop test A type of diagnostic procedure

which uses resistance through a bridge to locate an

"open" in a length of circuit It is similar to a Varley

loop test, except that instead of adjustable dials, one

arm is eliminated and a variable resistance arm

con-nected in its place, and a third wire is not required

See Varley loop test, Wheatstone bridge

Museum of Independent Telephony In Abilene,

Kansas, the home of the United Telephone Company

from 1898 to 1966, one of its former presidents, Carl

A Scupin, helped found the Dickinson County

His-torical Society and Museum The Museum of

Inde-pendent Telephony now shares premises with this

museum

tion adds about 3000 programs per year The museum

works in conjunction with the Museum ofTelevision

spon-sor seminars and exhibitions

Museum of Television and Radio in L.A Also

known as the West Coast Museum of Television and

Radio, it was established in 1995inLos Angeles This

museum is named after Leonard H Goldenson,

con-sidered a pioneer of the broadcasting industry It

works in conjunction with the original Museum of

music on holdBackground music on a phone line

that is heard when a caller is put on hold It can be

set up to play music from a radio, cassette tape, or

CD player, usually with a simple RCAjack near the

phone panel Recorded music is generally better, as

most radio stations play advertising, which is not

ap-preciated by most callers Some people don't care for

background music while on hold, but it's probably

better than not knowing whether or not you've been

cut off:

Musical Instrument Digital InterfaceMIDI MIDI

is a standard protocol for communication of sound

information through a number of specified

param-eters Functions provided on MIDI-capable

instru-ments are assigned numeric values which can be

digi-tally intercommunicated and remotely or locally

con-trolled MIDI capabilities are built into many

musi-cal editing and sequencing software programs

MIDI-compatible instruments generally have DIN

plugs for interconnecting the various MIDI devices,

and usually include MIDI in, MIDI out, and

some-times MIDI through A simple example of a MIDI

setup would be a keyboard connected to the fast

serial port or MIDI port of a computer with

MIDI-compatible software There may also be separate

speakers, since most computer and keyboard

speak-ers tend to be minimally useful for sound

reproduc-tion MIDI allows the songs from the keyboard to be

communicated to the computer and stored and edited

Conversely, compositions created on the computer,

sometimes including custom sound patches, can be

communicated back to the keyboard

MIDI is not the only music protocol, but it's definitely

the most widespread and best supported It is built

into numerous synthesizers, keyboards, drums, and

software music editing and sequencing programs

Musschenbroek, Pieter van See van

Musschen-broek, Pieter

MUT See MultiUser Talk

muteA feature or device that allows sound to be

turned off or lowered in volume Amute button on a

phone can cut out the sound to the mouthpiece so

something can be said in the background without

be-ing transmitted over the connected call (handy ifyou

have to call the dog or ask a co-worker a sensitive

question) A mute on a stringed instrument dampens

the vibrations of the bridge so that the sound of the

instrument is much softer

mutual capacitanceCapacitance is the capability or

inherent tendency ofan object or substances to store

composition and structure ofthe object or substance, but also to the environment within which the entity exists Influences from other objects will affect the capacitance ofan object and increase its capacitance

as they draw nearer to that object, hence the phrase

ex-ample, but one that helps illustrate this idea, think of

a satellite orbiting in space Asitdraws nearer the Earth, the greater is its tendency to be pulled by the Earth's gravitational field Similarly, with objects, the nearer they draw to another object, the greater is the tendency for capacitance, the capability to store a charge Capacitance is also affected by the medium that exists between objects Objects covered in plas-tic or a gel will have a different capacitance in rela-tion to one another than objects separated by air Thus, capacitance may be expressed as it applies to

a particular object but must also be taken into con-sideration as it applies to the atomic interactions be-tween two (or more) objects Ifthe objects come into contact with one another, or are connected by a con-ducting substance, then the capability to store up an electrical charge with relation to one other changes

in that the conducting surface effects a discharge or balancing of charges between the two objects

In general, electrical conductors have higher capaci-tance than, say, a block ofwood, but even people store

up electrical charges The human body acts as a ca-pacitor when it picks up electrical charges through friction contact with carpets, for example The next time you touch a conducting surface after storing up

a charge, you may feel a spark as the excess electri-cal energy in your body is rapidly discharged The extra charge is not always discharged quickly, how-ever If you hang around without generating a lot of friction with your feet nor having any contact with highly-conducting surfaces, you will still gradually discharge the stored up charge as it "leaks" more slowly into lesser-conducting materials such as the air, and wood or vinyl floors See grounding, static electricity, triboelectricity

MUX See multiplexer

MVIP Vendor Integration Protocol See Multi-Vendor Integration Protocol

MVL 1 Man Vehicle Laboratory A lab within the Center for Space Research (CSR) at the Massachu-setts Institute ofTechnology, founded in 1962 2 See Multimedia Virtual Laboratory 3 Multimedia and Visualization Laboratory See Multimedia Learning Laboratory 4 See Multiple Virtual Line

MVPmultichannel video programming.Anyof a variety of types of multiple-channel video program-ming genres, including television, network anima-tions, Internet streaming video, or video program-ming delivered through traditional or fast data-rate phone lines Due to the continued need to review, as-sess, and regulate video programming, the Federal Communications Commission prepared a report in

1999 on MVP that was released in January 2000 In its report, the FCC described a number of aspects of video programming, including the market share of

663

© 2003 by CRC Press LLC

Fiber Optics Illustrated Dictionary

different means of delivering programming, and

reiterated the beliefthat competition was the best way

to promote broadbased access to video programming

and competitive rates for the general public

MVPD multichannel video programming distributor/

distribution A broadcast distributor of a number of

video programming channels, usually provided

through cable TV or satellite feeds Broadband

In-ternet is now considered to be a viable distribution

channel See MVP

MVS Multiple Virtual Storage

MXR 1 mixer 2 multiplexer

myriametricMyriametric waves are associated with the very low frequency (VLF) transmission range (3 to 30 KHz) and occur naturally in auroral phenom-ena In the late 1980s, Home described the plasma-based terrestrial generation of myriametric waves

MZIMach-Zehnder Interferometer

symbol for a numerical quantity used to denote that

any number can be substituted in place of thenor,

quite commonly, n will represent any value within a

stated number set such as any positive integer (whole

numbers greater than zero) It is usually written in

ital-ics in lower or upper case Scalable solutions to

net-work configurations or database data sets are

some-times called n solutions to indicate that the system

can be expanded to handle exceedingly large

num-bers or quantities far in excess of what might be

needed in any given situation See N definition#4.

N 1 abbrev noise, usually as it pertains to signal

in-terference Thus,SIN represents signal-to-noise

ra-tio and C/N represents carrier-to-noise rara-tio

north-seeking end of a compass needle points to a

region near the Earth's North Pole called magnetic

north 3 symb "on," with F as the corresponding

symbol for "off." 4 symb the last component, value,

routine, link, or other virtual, conceptual, or

physi-cal aspect of a multipart system.Inthis context, it is

usually written in italics.Ina database, for example,

Nmay be the largest conceivable number of records

that might be expected to be needed or entered In a

distributed network,Nmay represent the largest

num-ber of hops that might be expected for a data

trans-mission path.Nis an important concept in both

pro-gramming and physical topologies The concept of

Nas a theoretical maximum enables planners to

de-sign and construct systems with the view of making

the system efficient within the perceived constraints

ofN.See n definition #2 See N definition #1.4 In a

Central Office telephone code, any integer between

2 and 9 See NXX

barrel-shaped cable/device coupler for interconnecting

com-ponents in a system or devices on a network N

se-ries connectors and adaptors come in a variety of

shapes and configurations from simple connectors to

extend the length ofa cable to adaptors to change the

"sex" of the cable between male and female to

ter-minators for establishing the end link in a series of

connections

N connectors are selectively coated in nickel, silver,

ryllium copper and typically support 50-ohm sig-nals (though 70-ohm versions are available) They are widely used for connecting radio frequency (RF) co-axial components

For Ethernet connections, 10Base-5 "thick" Ethernet cables with N connectors are becoming less common

in favor of 1OBase-2 "thin" Ethernet cables with BNC connectors or 1OBase-T twisted-pair phone-style

RJ-45 connectors See F connector

device (peripheral, computer, etc.) to be connected

as a node in a Fibre Channel network The N port is connected to the switched fabric port or F port The

N port is assigned a higher address than FL and NL ports and thus would have lower loop control prior-ity compared to these ports Aname server in the Fi-bre Channel fabric switch typically uses a discovery process to determine the fabric topology to obtain the addresses of other N ports for port logins

The N port may be built into the connected device or may be contained on an interface board, such as a PCI-compatible board in a computer High bandwidth devices, such as broadband storage devices, may have multiple Fibre Channel ports See F port, FL port, NL port

conduction-electron density exceeds the hole density The n materials interact with the p materials (the re-gion with corresponding "holes") at the p-n junction

in p-n semiconductors See p region, p-n junction

rec-ommendations providing guidelines for the mainte-nance of international sound programming and tele-vision transmission circuits These guidelines are available for purchase from thelTU-T SincelTU-T specifications and recommendations are widely fol-lowed by vendors in the telecommunications

indus-try,those wanting to maximize interoperability with other systems need to be aware of the information disseminated by thelTU-T A full list of general cat-egories is listed in Appendix C and specific series topics are listed under individual entries in this dic-tionary, e.g., K Series Recommendations See N Se-ries Recommendations chart

665

© 2003 by CRC Press LLC

Fiber Optics Illustrated Dictionary

node, device, link, router, hop, subroutine, loop, or

other virtual or physical link or component This

con-cept is important in many respects The

second-to-last link in a programming loop, a physical or virtual

network or other multipart system may have to be

handled or configured differently, given that the next

virtual or physical component in the system is the last

The penultimate item or data bit is often significant

in programming routines For example, in computer sorting algorithms, the number ofiterations required

in a particular function is frequently equal to N-l The handling of software stacks, dynamic groupings of stored data, also is related to the concept of the penultimate item or data grouping in the stack.In rou-tines where the program ends ifitreaches the last or

Ndata set, an awareness of reaching the penultimate

otherwise looping back and continuing program

ex-ecution See N definition#4.

num-ber of multiple applications or conditions or a

speci-fied limit that can be expressed as a positive integer

greater than one (1) in some situations and greater

than two (2) in others The limit may be explicitly

stated as ternary (three), quaternary (four), etc Ifthe

number is large, the actual number may be used, as

in 16-ary code in which 16 significant conditions

ex-ist The term is often used as a synonym for "many"

or "more than two" in general discussions where the

nmay be undesignated or unknown

hierarchies with a maximum limit ofnchildren in a

node

N-ISDN Narrowband ISDN, Narrowband Integrated

Services Digital Network Definitions vary but, in

general, Narrowband ISDN is used to refer to earlier

installations of ISDN providing lower data rates

through copper wires as opposed to newer Broadband

ISDN providing higher data rates through fiber

op-tic cables See ISDN for a fuller explanation

appears as a pair ofvertical blips coming from a

hori-zontal time base The direction ofthe target is inferred

by the amplitudes of the related vertical blips A

tar-get distance can also be determined by comparison

to a pedestal signal along the base line

NA 1 See naming authority 2 network

administra-tor/administration 3 See Night Answer 4 night

at-tendant 5 North America

NAB 1 See National Alliance of Business and

Na-tional Association of Broadcasters in Appendix G

NABTS See North American Basic Teletext

Speci-fication

NAC 1 Network Access Center 2 See Network

Access Control 3 See Network Applications

Con-sortium 4 See Numbering Advisory Committee

5 See null attachment concentrator

NACIC See National Counterintelligence

Informa-tion Center in Appendix G

NACN See North American Cellular Network

NADC See North American Digital Cellular

NADF 1 See North American Directory Plan

2 North Atlantic Directory Forum

cen-tered vertically below a remote sensing platform

name with its origin, location, or other relevant

char-acteristics In a network where a name has been used

as a mnemonic alias to allow easy recognition of an

address, application, or process, there needs to be a

mechanism to resolve the name into a form that can

be easily recognized and subsequently located by the

system.Inother words,mysite.comhas to be

trans-lated into a machine-readable address ofthe location

of the host site formysite.com.This is done through

name resolution, usually through a lookup table or

larger database Sometimes the name itselfwill

pro-vide some information about its origin or date of

es-characters assigned according to a system that can be understood by humans See naming authority

body that assigns names, usually as unique identifi-ers Various types of naming structures include hier-archical, flat, random, etc There are many well-known naming authorities: the U.S Library of Con-gress; R.R Bowker (ISBN); lANA (Internet) On the Internet, the various registered domains may assign subauthorities and subnames for local machines See lANA 2 In a hierarchical document management system, a tree of entities which provides a unique identifier to each document This task may be shared

by subauthorities

NAMPS Narrowband Analog Mobile Phone Service

An analog cellular communications technology which provides triple the capacity of an analog cel-lular voice channel by splitting the channel into 10 kHz bandwidth narrow bands Narrowband standards were released by the Telecommunications Industry Association (TIA) in 1992 (IS-88, IS-89, IS-90)

Digital mobile phone services are gaining ground on traditional analog systems See AMPS, DAMPS, code division multiple access, time division multiple access

NAMTS See Nippon Advanced Mobile Telephone System

NANC See North American Numbering Council

(North American system), or 10-9, that is, 000 000 001 See nanometer

Group

measure corresponding to one billionth (10-9

) of a meter A nanometer is one thousandth of a micron

Nanometers are often used to describe the size oftiny particles (e.g., chemical substances) or electromag-netic wave phenomena (e.g., laser wavelengths) Light waves at 534 nm are in the visible spectrum (appearing yellow to human senses; wavelengths are also commonly expressed in microns) Smoke par-ticles range from about 10 to 1000nIn.Electron mi-croscopes image up to maximum ranges of about 5

to 0.5 nanometers

With increasing miniaturization, the trend in the semi-conductor industry is to use nanometers instead of microns, with a number of major vendors announc-ing an official changeover in sprannounc-ing 2002

In synthetic materials fabrication, the region of 1 to

100 nanometers is of particular interest as it is less well understood and is subject to interesting interac-tions between molecular and macroscopic prop-erties

Distances traveled by certain phenomena such as seis-mic waves may be described in terms of nanometers per second (nm/sec) See

nano-NANP See North American Numbering Plan

NANPA See North American Numbering Plan Ad-ministration

NAP See Network Access Point

667

;••.~";>~,;> •.~.,• • • "• ••l •_.

>.-;.

::~::; :".

;;~~

© 2003 by CRC Press LLC

Fiber Optics Illustrated Dictionary

NAPPSee National Aerial Photography Program in

AppendixG

NAPT Native American Public Telecommunications,

Inc

se-cured or unsese-cured natural language

communica-tions For example, in military space programs, the

Special Communications Systems is a realtime,

au-tomated communications system on which narrative

messages can be composed and edited The Global

Command and Control System (GCCS) is a secured

system capable of handling narrative and data

traf-fic During times ofemergency when traffic over

net-works is suppressed, narrative traffic may alternately

be sent by other means such as courier

depending upon the industry and its bandwidth needs,

and on the current state of technology Narrowband

usually represents the lower end of the available

ca-pacity or spectrum of a system In some cases it is

used to denote a single band within a multiplexed

group of bands sent more-or-Iess simultaneously In

traditional telephony, it represents a sub-voice-grade

line In cellular communications, it represents one

division of the broadcast spectrum consisting of a

channel frequency (CF) ofabout 30 kHz, usually

ac-complished through frequency division duplexing

(FDD) See AMPS, NAMPS

NAMPS

speeds up to 64 kbps, which is fine for voice and some

data communications, but only adequate for

applica-tions like full-motion video, or video and sound

Ef-forts are being made to incorporate new standards into

broadband ISDN (B-ISDN) that will remove the fixed

channel structure limitation of narrowband ISDN

tar-gets specific people and often specific services to

those people Ifbroadcasting is considered to be

pro-gram delivery to a wide and sometimes scattered

au-dience, from one to many, then narrowcasting can be

seen as one to one or one to few For example,

elec-tronic industries' personnel might subscribe to

pro-gramming on circuit board fabrication At an even

more specific level is "pointcasting," that is, program

services which target user-selected information, a

type of electronic clipping service providing

elec-tronic information on specified topics of interest

Tele-communications Engineers in Appendix G

NASSee network-attached storage

NASASee National Aeronautics and Space

Admin-istration in Appendix G

Evaluation Cooperative (SPEC) benchmark used in

scientific and engineering applications Abenchmark

tends to be a specific quantitative measure of a

par-ticular aspect of system functioning, and by itself

conveys a limited picture of overall system

perfor-mance However, in the specific context for which it

is intended, a benchmark can provide valuable

infor-mation for design engineers, researchers, and manu-facturers Nasa7 generates input data, performs one ofseven floating point-intensive kernel routines, and compares the results against an expected reference measure It is used to evaluate performance, memory,

VO operations, and networking factors See

bench-mark, Rhealstone, Whetstone

Project A project of the National Storage Industry Consortium (NSIC) to explore, validate, and docu-ment the technologies needed to enable the deploy-ment ofnetwork-attached storage device systems and subsystems The project was initiated because the trend towards large distributed networks is causing people to rethink the most efficient ways to imple-ment storage capabilities, and more networks are us-ing remote rather than local storage to handle large data repositories Fibre Channel is seen as one of the technologies appropriate for fast-access remote stor-age See National Storage Industry Consortium

commu-nications-related organizations prefaced with "Na-tiona!."

National Center for Supercomputing Applications

NCSA Aresearch center at the University ofIllinois, best known for the development ofNCSA Mosaic, the historic Web information browser that preceded Netscape Navigator

when old telephone codes and numbers were changed

to revamp the system New codes and telephone num-bers became available in August 1994 and the Code Change took place in April 1995 On the same day, the dialing code for international calls originating in the U.K changed from 010 to 00

to safeguard public safety and property from hazards associated with the use of electricity This includes wiring and electrical device construction, materials, installation, and maintenance and is adoptedinmany parts ofthe country as law for various building, equip-ment, and utility pole (below supply space) installa-tions The Code is developed by the American Na-tional Standards Institute (ANSI) and is published by the National Fire Protection Association (NFPA) See National Electrical Safety Code

gov-erning electrical facilities located in public rights-of-way to ensure the safety of the public and installa-tion/maintenance professionals It is published by the Institute of Electrical and Electronics Engineers (IEEE) See National Electrical Code

three data and information centers of the U.S Na-tional Environmental Satellite, Data and Information Service (NESDIS)

pro-posed many times over the decades for a variety of

to the concept, with concerns about security breaches

(people using the information in unethical ways to

access private information in centralized databases),

loss, replacement, forgeries, and more In a sense,

NationalillCards already exist for non-American

legal residents (and a NationalillCard doesn't solve

the problem of illegal residents)

The commonly called Green Card (Immigration Visa

for Resident AlienslPermanent Residents) is a

bio-metric national identification card issued over the

course of many decades that includes a photo and a

fingerprint (biometric identifier) tied to a federal

da-tabase that already serves the purposes most people

want a National ID Card to cover To get a Green

Card, you have to provide birth, background,

educa-tional, and other personal information to the U.S

fed-eral government and be approved through a

back-ground check and interview, which is usually repeated

approximatelyevety 10 years Asking evety U.S

citi-zen to also carry a NationalillCard in addition to

the many driver's license/passport/birth certificate/

social security documents already· issued calls to

question why yet another card should be issued and

how it would be any different or better than the

docu-ments already routinely carried Some people have

even compared it somewhat radically to skin

brand-ing

A National ID Card can be easily lost, as with any

other card, and fall into the wrong hands

Wrongdo-ers often use forged or stolen documents; this might

give them one more document to forge or steal and

may not have any substantial security benefits in

re-lation to the increased security risks associated with

the loss of the card Nevertheless, after the events of

September 11, 2001, the issue of Nationalillcards

has again been brought fOlWard and will no doubt be

debated for a long time In the world of electronics,

where the infonnation on theillcard may be directly

linked to a powerful central database, it must be

care-fully weighed whether a National ID Card program

should be undertaken, especially given that, once the

database exists, it may over time be commandeered

for other purposes by future governments, or

even-tually be used by law enforcement agencies to track

and profile individuals without their knowledge

Stranger things have happened in the past

National Information InfrastructureNIL The

name for the political, administrative, and physical

underpinnings ofan interconnected collection

ofpub-lic and commercial national narrowband and

broad-band data networks One of the biggest stakeholders

in the NIT is the National Information Infrastructure

Advisory Council (NIIAC), established in 1994

through a 1993 executive order The NlIAC is

respon-sible for advising the government on a national

strat-egy for promoting development of the Nil and the

Global Information Infrastructure (Gil)

The NIl is a physically and regionally diverse

sys-tem which is considered as a whole, mainly on the

basis ofinterconnectivity It includes small and large

networks, wireless and wireline connections, public

ganizations and individuals The Nil is also known

by the catchphrase "Information Superhighway," al-though this describes the communications aspect of the NIl and could be considered a subset

National Public Broadcasting ArchivesNPBA Housed at the University of Maryland in the Hornbake Library, the NPBA started as a coopera-tive project of several broadcasting and educational institutions.Itwas initiated by Donald R McNeil, a Public Broadcasting System (PBS) board member, and officially dedicated in June 1990 NPBS provides

an archival record of major documents and selected programming from U.S noncommercial broadcast-ing history

http://www.lib.umd.edulUMCP/NPBAI

National Public RadioNPR A major award-win-ning producer and distributor of public radio broad-cast programs developed by independent producers Based in Washington, D.C., NPR provides popular shows such as All Things Considered, Car Talk, and Morning Edition plus NPR hourly news on the In-ternet.Italso hosts lively discussion groups online about issues raised on NPR programs See Public Radio International http://www.npr.org/

National Spatial Data InfrastructureNSDI.AU.S

di-rectly or indidi-rectly, using the Federal Geographic Data Committee (FGDC) standard

National Television System CommitteeSee NTSC

NATOASee National Association ofTelecommuni-cations Officers and Advisors in Appendix G

natural antenna frequencyAn antenna's lowest natural resonance frequency when operated without external capacitance or inductance

natural frequencyThe frequency at which an oth-elWise uninfluenced or unimpeded body will oscil-late when stimuoscil-lated to move Knowledge ofnatural frequencies is important in structural engineering and scientific research

The collapse of"Galloping Gertie," the Tacoma Nar-rows bridge is one ofthe more spectacular examples ofhow natural frequencies must be considered when building large or safety-oriented structures The Tacoma Narrows bridge collapsed because ofthe in-teraction of a windstorm with the natural frequency

of the bridge's movements Without holes in the sidewalls to let the wind pass through, the accumu-lation of the bridge oscilaccumu-lations from the wind caused

a resonance wave so great,ittore the bridge apart

Natural frequencies aren't always harmful They can

be helpful tools for sensing devices Many structures exhibit natural frequency vibrations that can be sensed with seismic instruments or light-based sen-sors It has been proposed that fiber optic sensor ar-rays could be built into bridges and buildings to pro-vide readouts of natural frequencies over time In fi-ber optic sensors with micromechanical resonators (e.g., those made from metallic glass), a measured

669

© 2003 by CRC Press LLC

Fiber Optics Illustrated Dictionary

parameter (temperature, pressure, force, etc.) is

ex-pected to change the microresonator 's natural

fre-quency which may be both excited by and detected

by light This, in tum, provides data about the

phe-nomenon or object sensed

natural logarithm See logarithm

magnets One is a substance that exhibits and retains

magnetic properties without application of a current

after it has been magnetized with another magnetic

source The second is a substance which exhibits

magnetic properties as it comes out of the ground,

without needing to be exposed to magnetic influences

for it to become a magnet The second type of

per-manent magnet is called a natural magnet See

lode-stone

corre-sponds to an antenna's natural frequency Matching

an antenna's resonant frequency to the

characteris-tics of the wave being received (or transmitted) is an

important aspect of antenna design

(GPS) satellites operated by the U.S Department of

Defense, whose navigational signals are available to

civilian users See Global Positioning System (GPS),

GLONASS, Standard Positioning Service

maritime navigational warning distribution system

NAVTEX sends warnings to ships as they move in

and out of areas for which broadcast information is

available that may be relevant to marine safety See

Global Maritime Distress and Safety System

of satellites moving in polar orbits about 700 miles

above Earth, which preceded the Global Positioning

System (GPS) used today NNSS Doppler

technol-ogy could compute group positions on or around the

Earth to about I-meter accuracy by means of

mul-tiple readings The long time between transits over

the same location (about 90 minutes), and the

diffi-culty of determining instantaneous velocity led to the

development ofthe GPS system See Global

Position-ing System

NBC See National Broadcasting Company in

Appen-dixG

NBFCP See NetBIOS Frames Control Protocol.

NBFM narrowband frequency modulation.

NBMAnonbroadcast multiple access

part of the DNS specification that deals with

cach-ing the nonexistence ofa domain name or RRset, thus

reducing message load and response time for

nega-tive answers With the growth of network traffic and

increased need for quick and frequent resolution of

domain names, the importance of negative caching

has grown to the point where it was suggested by

Andrews and others that negative caching be routine

rather than optional See negative caching, RFC 1034,

RFC 2308

NCCS Network Control Center System

NCIAnative client interface architecture An SNA

applications-access architecture developed by Cisco

Systems NCIA encapsulates SNA traffic on a client computer, preserving the user interface from the na-tive SNA system so that the end-user can work in a familiar environment and also have directTCP/IP

ac-cess

NAVSTAR GPS Satellite

The 19th NAVSTAR satellite was launched in 1993.

on board an Air Force Delta11craft The NAVSTAR satellites are usedfor GPS data and geodesic research [NASA/Marshall images.}

Technology Standardization

NCOSee National Coordination Office for Comput-ing, Information, and Communications in Appendix G

NCOPNetwork Code Of Practice

NCSA 1 See National Center for Supercomputing Applications in Appendix G 2 National Computer Security Association Now the International Com-puter Security Association

browser and World Wide Web client developed at the National Center for Supercomputing Applications Mosaic was the predecessor to Netscape Navigator distributed by Netscape Communications Navigator was later declared open source software See Mosaic for a fuller history; see Netscape Navigator

NDISSee Network Driver Interface Specification

NDSISee National Spatial Data Infrastructure

NDTI network downtime In telephony, the elapsed time from when network managers become aware of

a problem until the moment at which the subscriber's service is restored.Incomputer networking, the time during which normal processes are unable to execute due to electrical outages, software crashes, network link disconnections, processing overload, malicious tampering, or unintentional bugs that interfere with processes outside ofthe application that has the bugs

2 No Dial Tone

near end crosstalkNEXT When wires are packed

tightly together, and signals are traveling through

most or all of the wires, especially in two directions,

the signals originating at one end can exceed or

in-terfere with weaker signals coming from the other

end, resulting in crosstalk With much higher speed

transmissions media, such as gigabit Ethernet, which

involve bidirectional signals in more complex

sys-tems ofaggregated wires, this can be a severe

impedi-ment One means of compensating for NEXT is to

include a NEXT canceler, which detects and adjusts

for noise in the circuit See far end crosstalk

of the electromagnetic spectrum that has slightly

shorter wavelengths than the visible spectrum

per-ceived by humans as the color red Certain snakes and

insects have infrared-sensing receptors Humans tend

to sense infrared as thermal energy (heat) In general,

near-infrared has frequencies ranging from about 700

to 3000 nm Commonly-available commercial

ach-romatic lenses are generally in the 700 to 1500 om

range There are many filters designed to selectively

include or exclude infrared radiation and some

pho-tographic filters selectively admit infrared radiation

for specialized applications

Infrared light is suitable for many types of data

trans-fer and is commonly found in wireless remote

con-trols and light-based wireless computer networks It

is widely used in remote sensing applications such

as astronomy and in fiber optic communications

sys-tems NIR-based spectroscopy is useful for

materi-als analysis in a wide range ofchemical and

pharma-ceutical applications See infrared

or acoustic waves, the region near a source wave or

reflected wave that is less than the length ofone

wave-length Since there may be many wavelengths

present, a specific frequency may be selected (which

may be the strongest, the most central, or the most

relevant to a particular task), or an average or other

estimate ofa range ofwavelengths may be calculated

to provide a nearfield estimate If a range of

wave-lengths is being studied, the concept of nearfield is

sometimes broadened to include the median or

long-est wavelength within the range and the interactions

that occur between the wavelengths (e.g., diffraction)

Thus, the nearfield is context-specific but, in general,

inversely related to the wavelengths of interest

Concepts of nearfield are important in observing or

scanning radiant energy at very close ranges as there

are special problems associated with collecting

undistorted data from incomplete or interacting

wave-lengths In laser technologies, measures such as beam

width and beam separation or divergence from the

intended path are also more difficult to calculate in

the nearfield, but these calculations may be

impor-tant in tasks such as aligning fiber optic light sources

See nearfield imaging, nearfield diffraction

at very close range In electromagnetic imaging, it is

a region in which the observing/recording device is

wavelengths may interfere with the process (e.g., by interacting with one another) or may be longer than the distance between the sample and the observing/ recording device This poses special problems in achieving undistorted viewing Nearfield imaging is

a challenge in many fields, including microscopy and spectroscopy

Many of the same nearfield imaging issues apply to the monitoring of acoustic phenomena very near to the source of the sound waves

There are a number of ways to tackle the challenge

of nearfield imaging Imaging at a range of frequen-cies and combining and processing the data may yield averages or patterns that provide information about the imaged sample Hypercooling may reduce mo-lecular movement, thus removing or reducing poten-tial sources ofinterference Using a fiber optic probe

or taper to draw the image away from the surface is another strategy See diffraction, Rayleigh scattering

Diffrac-tion in which electromagnetic waves incident upon

an obstruction are diffracted in spherical waves origi-nating from a point source Since spherical waves overlapping any type of waves results in some com-plicated interactions, it can be challenging to calcu-late and mathematically model Fresnel diffraction Fresnel diffraction must be taken into consideration

in the design ofantennas, imaging technologies (e.g., nearfield spectroscopes), and other devices in which there are radiant or reflective elements that are proxi-mate and likely to have radiating energy that overlaps For experimental purposes, a laser light source can

be converted to a spherical light source by use of a lens and a small opening to spatially filter the light down to a point light source See diffraction, Fresnel region

NECSee National Electrical Code

NECASee National Exchange Carrier Association neckThe narrow portion ofa cathode-ray tube (CRn

at the end where the electronbeamsare emitted from the cathode

negative acknowledge, negative acknowledgment NAK A commonly used international communica-tions control character which indicates that data was not received, or not received so that it could be un-derstood This is common to handshaking protocols,

in which an acknowledgment is required before the sender can continue See acknowledge

a control grid to make it hold more of a negative charge than the electron-emitting cathode Manipu-lation of the control grid is what makes it possible to control the flow of electrons from the cathode to the anode, and thus to create different types of circuits and effects

the nonexistence of an object, entity, or service The availability ofthis information can reduce the time it takes to determine the components or configuration

of a system or file Negative caching statistics are commonly stored in tables or headers, depending on

671

© 2003 by CRC Press LLC