mail bomb Avandalistic or retaliatory transmission sent through network email protocols with the inten-tion of disabling an email address, the system upon which the address resides or, a
Trang 1Fiber Optics Illustrated Dictionary
With optional air- or water-cooled heads, different
kilowatt output levels may be selected See
Barkhausen-Kurz tube, cathode-ray tube, cavity
mag-netron, Klystron, traveling-wave tube
magnetron historyGermany, Japan, and America all
contributed to the development of the magnetron in
the 1920s and 1930s Its origins date back to the work
ofH Barkhausen and K Kurz in Germany, who
de-scribed the shortest waves that could be produced by
vacuum tubes, in 1920 The invention of the
magne-tron itself is attributed to Albert W Hull, who
de-scribed it publicly in the AlEE Journal, in 1921
Au-gust Zacek may have made similar discoveries in the
early 1920s, as he ordered several special diodes
which could have been used to study electron
oscil-lations.In Japan, Kinjiro Okabe proposed a divided
anode-type magnetron in 1928 that helped further the
practical applications of the magnetron In 1935, A
Arsenjewa-Heil and O Heil described the concepts
ofvelocity modulation and spatial bunching In 1937,
William Hansen and the Varian brothers designed and
built a prototype Klystron tube, capable of
generat-ing microwaves; they announced their invention in
1939.In Japan, Kiyoshi Morita ordered magnetron
prototype tube from JRC and there was close
coor-dination between the Naval Research Institute and
JRC in the mid-1930s for building magnetron tubes,
directed in part by Shigeru Nakajima, resulting in a
water-cooled, single-phase, 500-W oscillator, in
1939 In November 1939, John Turton Randall and
Henry H.A Boot announced the frrst cavity
magne-tron; within four years, it had become an important
aspect of radar technology
In the 1940s, Percy LeBaron Spencer noted the
magnetron's ability to produce thermal energy in
sub-stances exposed to the microwaves, while
research-ing magnetron radar applications This led to the
de-velopment of the microwave oven for which he
ap-plied for a patent in October 1945 (U.S #2,495,429)
Early microwave ovens were called "radar ranges."
As magnetrons became practical for industrial use
after World War II, they were combined with
genera-tors for manufacturing applications such as surface
coating(sputtering) Industrial use continues today
in flat panel display manufacturing and other
fabri-cation applifabri-cations where frequency stability at a
spe-cific wavelength is important
Magnetrons and solidstate electronics continued to
be developed in the 1960s and 1970s, lowering the
price and size of the components Thus, microwave
ovens became a common magnetron-based
house-hold product by the 1980s
Magnetrons also have some novel uses in military
defense In the 1980s, theu.s.Air Force developed
a tunable magnetron for imitating radar signals to
draw enemy missiles from their intended targets
Today, magnetron technology is important in
satel-lite communications and industrial fabrication
ofop-tical components See magnetron sputtering
magnetron sputtering Aphysical vapor deposition
process for coating metals, alloys, compounds, glass,
and films using a coating chamber, a pump, and one
or more magnetron generators to deposit fme layers
of coating The component being coated may be placed on a rotating table or a stationery jig Fiber optic temperature sensors may be used as a process control component in sputtering chambers
Since many optical instruments include coated com-ponents and thin films, sputtering is an important as-pect of optics fabrication
In the 1980s, Teer Coatings Ltd developed an indus-trial coating system based upon two or more proxi-mate magnetrons with opposing magnetic polarities This configuration creates an active deposition zone within which the interacting magnetic fields can trap the ionizing electrons, resulting in superior coating efficiency over traditional single-magnetron systems
In the late 1990s, Makowiecki and Jankowski pat-ented a sputtering process for producingthin boron-based films that have potential as ultrathin-bandpass filters and as low-radioactive elements in optical com-ponents
MAHOSee mobile assisted handoff
mail bomb Avandalistic or retaliatory transmission sent through network email protocols with the inten-tion of disabling an email address, the system upon which the address resides or, at the very least, to greatly inconvenience or annoy the recipient Mail bombs take many forms, but the most common is a repeated message that eventually floods the recipient's email storage space or the storage space
on the recipient's service provider's system, depend-ing upon how it is partitioned
Mail bombs are often sent to people who post absurd messages on public forums, or to originators ofjunk email (unsolicited email, especially ofa commercial nature) to express the extreme displeasure of the re-cipients receiving thejunk email Amail bomb rarely solves the problem, however, since recipients often retaliate See flame wars, spam
mail distributor Anagent, script, macro, or filter that takes incoming mail, evaluates the headers or other pertinent information, and distributes the mail accord-ingly Thus, a single message might be forwarded to
a number of users, different messages may be fun-neled to a single user, or groups may be set up to re-ceive certain types of messages The messages may include certain topics, which are keyed and processed,
or may include priority or security information, which
is handled accordingly A mail reflector is the sim-plest type of mail distributor, which passes on mail with a minimum ofevaluation and processing ofcon-tents (usually only the TO: header)
A mail distributor can be a big time saver when it is used to fOlWard email to a mailing list or a discus-sion list.Anaddress or database entry in the mail dis-tributor can be used to expedite distribution to many recipients This should not be used as a means to dis-tribute junk email, more commonly knoWn on the Internet as "spam," as there are regulations against this type of use, and users do not appreciate receiv-ing it (many will boycott companies distributreceiv-ing com-mercial mail in this way) See discussion list
mail filter Asoftware utility or feature of an email
Trang 2cipient, subject line, or content of a letter to sort it
into designated categories Mail sent to a specific
domain name is often filtered by companies to
indi-vidual employees' email accounts; junk email
mes-sages are often filtered out, and sometimes deleted
unread Some people filter personal and business mail
into separate directories before reading the messages
Mail filters are a great convenience and worth the
time it takes initially to set them up
mail gatewayAlthough there are standardized
pro-tocols for the distribution ofemail over networks, not
all systems use the same protocols, and not all
proto-cols are implemented in the same way Thus, when
mail passes from one system to another, if there is a
mismatch, there needs to be a way to resolve the
dif-ferences, or to tunnel or encapsulate the messages so
they can reach the recipients Amail gateway is a
sys-tem in a computer network that handles mail
channel-ing or the resolution ofprotocols
mail list agentMLA In SDNS Message Security
Protocol (MSP), a mail list agent is one addressed by
the message originator that represents a group of
re-cipients It provides message distribution services to
the participants of that group on behalf of the
mes-sage originator
mail list keyMLK In SDNS Message Security
Pro-tocol (MSP), a mail list key is a token held by all the
members ofa mail list, or by a mail addressable group
within the list
mail readerAsoftware program which permits email
to be downloaded from a host system and read
off-line, so as not to incur connect charges or tie up a
phone line Most mail readers are actually mail
read-ers and writread-ers, and can be used to respond to the
re-ceived messages or to compose new messages They
may also include filters to preorganize the mail
be-fore it is read, and a database interface which allows
the messages to be organized and stored for later
re-trieval
Some mail readers have been enhanced for use as
online news readers as well, for following discussion
threads on USENET and for posting to the various
online lists Posting is the same as sending email,
except that the message will be publicly available and
may be read by thousands or millions ofreaders Pine,
developed by the University of Washington, is one
of the most popular mail readers It is freely
distrib-utable, allows flexible processing of mail messages
and files, and includes news reading and posting
ca-pabilities See email, USENET
mail reflectorA mail node set up to pass messages
on according to a predefined list It does only the
minimum processing needed to forward the mail to
its intended recipients For information on more
so-phisticated processing, see mail distributor
mail serverA software system which manages
in-coming and outgoing electronic mail on a network
Mail servers vary in complexity and features, but
most will check the validity of an address; queue,
deliver, and store messages (or return them ifno valid
address is found); forward mail, etc
email on the Internet, some of the newer mail serv-ers will check the validity ofthe sending address, and reject the mail if the sender does not appear to be le-gitimate This may result in the loss ofsome real email messages: for example, ifsomeone is about to change email addresses and close out an old account, he or she may send email letting you know the new address, then subsequently close the account before the mes-sage reaches its destination The server may reject the legitimate message However, some consider the trade-off worthwhile, in order to deflect the thou-sands, or sometimes tens of thousands ofjunk mail messages that now flood the systems of most ISPs
See email.mailgateway.mail reader
mailboxThe part of an email client/server software system that comprises addresses and files which store electronic mail Web browsers and dedicated mail processing software programs typically enable the management of multiple user mailboxes Many In-ternet Service Providers will offer multiple mailboxes
to their subscribers (e.g., six mailboxes per personal account) Many business accounts offer unlimited mailboxes
~~f~s~!0Ei:~::Es~~~~i ~t~~*t:~~!'JI
a Web browser to send a message to the person or organization mentioned The format to set up the hypertext link is:
Click to send email to<A HREF =
"rnailto:stan@company.com"> Stan</A>
In the above example, the name Stan will be high-lighted in the Web browser to indicate that it can be clicked When it is clicked, the browser will launch the user's email client, usually inserting the destina-tion address automatically (stan@company.com), and enables a message to be written and dispatched to Stan without closing down the browser It's very con-venient but is falling into disuse because ofjunk email abuse - robot Web crawlers have been designed to quickly seek out mailto addresses on millions ofsites, automatically adding them to junk emailing lists See RFC 822, RFC 1738
Maiman, Theodore Harold (1927- )An American physicist at Hughes Research laboratories who de-veloped and patented aruby-based laser He described
his pioneering laser research in Nature in1960 In
1962,Maiman founded Korad Corporation to re-search, develop, and manufacture lasers He eventu-ally sold this firm to Union Carbide and formed Maiman Associates in1968.Maiman is a member of numerous scientific professional organizations and has been awarded many prestigious prizes for his contributions to lasers See laser
main distribution frameMOF Acentral wiring con-nection point in a larger more complex wiring sys-tem that includes more than one distribution frame
The main distribution frame is the one which con-nects the internal wiring with the external wiring
Within the premises, there may be secondary
Trang 3Fiber Optics Illustrated Dictionary
distribution frames in each department or each floor,
depending upon the electrical needs and building
con-figuration See distribution frame
main memoryIna computer, there are sometimes a
variety of types of memory, and there may be more
than one memory bank On some systems, where all
the available memory is addressable by the system
without significant restrictions, the concept of main
memory is not important, as all memory is main
memory However, some systems make a distinction
between system memory and expansion memory, and
it may not be possible to address all the memory as
one contiguous area These systems treat the first
memory, that which is addressed by default or used
as first priority, as main memory Extra memory for
video display and other specialized uses is not
con-sidered main memory as it is not used as
general-pur-pose storage by the system
main station This is a loosely defined phrase because
it is context-specific The people within a system
of-ten have a tacit understanding ofmain station
facili-ties and the definition varies widely, depending upon
the industry 1.Intelephony, a user telephone set or
terminal with a unique call designation used for
origi-nating calls and accepting calls on an exchange If
there are extension phones with the same phone
num-ber, one is usually designated as the main station 2
In computing, an "intelligent" workstation (as
op-posed to a "dumb" terminal, for example) installed
with a full set of capabilities or which functions as a
primary or secondary server Amain station may also
be a terminal with access to resources that may be
otherwise restricted within the local facility, such as
scanners, printers, modems, etc 3 In broadcasting,
a primary sending or receiving station, as opposed
to a specialized or lower-resource relay station A
main station is more likely to be staffed or to have
significant technological or broadcast power
capabili-ties compared to other stationsinthe system Amain
station is not always the largest or best-equipped
sta-tion in a system; it may also be a clearinghouse or
storage unit for a significant number of broadcasts
or broadcast recordings, or it may be the
highest-power station or one located on the highest
promi-nence in the network
mainframe The terms mainframe, miniframe, and
workstation are all relative The most powerful
com-puters in the world are called supercomcom-puters, and
the less powerful computers that are above the
con-sumer or workstation price range are called minis or
miniframes Mainframes fall between these two
cat-egories In general, mainframes are typically the
larger, more expensive, more powerful, faster systems
with more storage capacity and the ability to handle
many users on a network Workstations and
micro-computers are often used as smart terminals in
con-junction with mainframes Mainframes are used in
larger educational institutions, large businesses, and
scientific research facilities Current consumer-priced
desktop microcomputers are more powerful than the
mainframes available 15 years ago
mains A primary commercial alternating current
(AC) power supply In North American domestic power grids, mains power is typically single-phase power routed through a breaker box to internal wir-ing Triple-phase power is also available in some ar-eas, usually carrying higher voltages Mains electric-ity is used to power appliances, lights, heating units, industrial facilities, safety devices, etc
Mains AC voltage for North America, South Korea, and parts of South America is 100 to 120V at 60 Hz
In Japan, it is 100V at 50 and 60 Hz Mains AC volt-age in Europe is around 220 to 250V, depending upon the country, with a target goal of 230V at 50 Hz by
2003 for unified Europe One of the reasons for the many different types of electrical plugs in different countries is to prevent electrical shocks, fires, or dam-age to components resulting from the varying elec-trical properties of the mains power
Increasingly, radio frequency (RF) signals are sent over mains wiring within buildings This enables con-sumers to transmit audio, visual, and control (e.g., XI0 components) signals through the wiring to other locations in the building without running dedicated wires or worrying about low-power wireless signal attenuation through walls and over distances While this was not a problem in the past, the increasing use ofmains for secondary signaling may become a con-cern as a source of interference
In some cases, such as industrial applications, the power coming from the mains may not be exactly what is needed The power may be conditioned to meet specific industrial or electronic needs For use with sensitive electronic equipment, mains energy is often channeled through surge suppressors and trans-formers to filter and convert the energy Many elec-tronic devices require only 4 to 12V, far less than is coming from the mains supply and would be burned out without appropriate conversion
Power does not always come out ofthe National Grid mains line; sometimesitis directed into the Grid Alternate energy sources such as wind turbines some-times generate more electricity than is needed and the surplus may be directed to the mains, depending upon power agreements and regulations in the area maintenance termination unit MTU.Anelectronic diagnostic device installed at a line termination unit (LTD) of a premises installed with telecommunica-tions equipment, usually by the line provider The MTU typically performs circuit tests for short circuits
or open circuits that may be remotely monitored This aids network operators in locating the source ofa fault
and detennining whether the problem exists on the
customer or connection side of the LTU Multiple MTUs may be installed along a subscriber line to
fur-ther pinpoint fault locations
Major Trading Area MTA A service area designa-tion adopted in the early 1990s by the Federal Com-munications Commission (FCC) based upon an older Rand McNally classification of u.S metropolitan regions MTAs were identified by the FCC to admin-ister and license wireless Personal Communications Services (PCS) There are over 50 MTAs in the U.S., built from contiguous Basic Trading Areas (BTAs)
Trang 4somewhat important in administering wireless
ser-vices, since the frequency ranges must be reused as
efficiently as possible to provide service to as many
areas and individuals as possible
The FCC provides a Market Area cross reference that
enables a user to search by MTA, BTA, or state and
county to find corresponding markets Thus, an MTA
can be used to find corresponding BTAs or counties
For example, a search of the New York MTAyields
a list of 20 BTAs, from Albany to Watertown, which
are further linked to a list ofcounties within the BTA
http://www.fcc.gov/
Majordomo A widely used software program that
automates the management of Internet discussion
lists, developed and licensed by Great Circle
Asso-ciates (GCA).Itenables the remote administration
ofemail list subscriptions, electronic mail messages,
digests, and archives Thousands ofMajordomo lists
are online, many with tens of thousands of
subscrib-ers Lists may be open, private, or moderated List
management is handled through electronic mail
(email) Some people call them mailing lists, but it is
best to make a distinction between discussion lists,
which are for the exchange of information and
de-bate, and mailing lists which are used by marketing
agents to email advertising messages
The name is derived from head domestic or butler,
the traditional manservant or master who handled
visitors and the oversight ofa house (domicile)
Simi-larly, Majordomo does your bidding and handles your
affairs, leaving you free to concentrate on
communi-cations with discussion list guests
Majordomo source code is written almost entirely in
Perl, making it possible for programmers to modify
the source for their needs within the terms of the
Majordomo License Agreement Majordomo runs on
a wide variety ofUnix platforms and a Web interface
is available as an add-on Majordomo source code is
available for free download within the terms of the
licensing agreement Version 1.94.5 was released in
January 2000 and Jason Tibbits is developing
Major-domo version 2 See LISTSERV
http://www.majordomo.com/
Make Busy Asubscriber service or feature ofaphone
that causes the line to send a busy signal to an
incom-ing call This is like takincom-ing a line off the hook
with-out removing the handset While this might seem like
an odd thing to do, it can actually save people money
If a business has more phone lines than agents ready
to take calls (e.g., at lunch time), it may be better to
send a busy signal than to let it ring indefinitely or to
answer and put the caller on hold for a long time
(which people don't appreciate) Ifthe callers are
di-aling long distance, it can save them the toll charge,
since the call is not answered
Make Busy is also helpful to the receptionists on duty,
since it can reduce the number ofincoming calls to a
manageable level Depending upon the service, Make
Busy can be assigned to one or more lines within a
hunt group See Ring Again
malicious call A telephone call with annoying,
abu-malicious calls are unlawful, but it may be difficult
to prove the malicious content of the call, especially since wiretapping laws generally prevent the caller from being taped without his or her permission
In general, telemarketing calls are not considered malicious unless the caller is promoting illegal prod-ucts or promoting them in a harassing or intention-ally deceptive manner Upon seeking help with ma-licious calls, you will generally be advised not to take the phone off the hook, but to answer it repeatedly and to immediately and quietly hang up, no matter how many times it takes If the malicious caller ut-ters what appear to be genuine threats, it is advisable
to inform the phone company, the police, and other members ofthe household or office Ifthe malicious call appears to involve fraud, inform the phone com-pany, the police, relevant consumer associations, and other members of the household Some phone com-panies have call investigation centers that can assist the police with trapping and tracing persistently ma-licious calls, especially those ofa threatening nature Malus's law When a beam of light that has already been once polarized by reflection hits a second
sur-~:~~:;;~:::~~:~~~1~~~~ili~;~;·. MAN See Metropolitan Area Network
Management Information Base Mm Aset of data modules which contain the definition of a related set ofmanaged object types In SNMP management sys-tems, it contains the logical names of informational resources on the network In SONET network imple-mentations, objects in the Mffi are defined with a re-stricted subset of Abstract Syntax Notation One (ASN.l) as to their name, syntax, and encoding
Management Information Services MIS Corporate communications professionals whose job is to facili-tate the acquisition, flow, use, storage, and retrieval
of information within an establishment
Mance, Henry Christopher (1840-1926) ABritish engineer who adapted the Indian heliotrope to a he-liograph daytime signaling system using mirrors mounted on tripods The angle of the mirror could convey line-of-sight dot and dash signals up to 100 miles This system was used for military communi-cations for several decades
Manchester encodingAnencoding scheme com-monly used for baseband signaling in coaxial cable transmissions, especially 1OBase-T network systems
There are variations to the encoding, but a typical differential Manchester employs a voltage transition
in the middle of a bit period A zero is represented with an additional transition at the beginning ofa bit period A one is represented with no transition at the beginning of a bit period
There is a tradeoff between bandwidth and binary coding, as the coding consumes part ofthe bandwidth
InManchester encoded transmissions, the amount of useful bandwidth is about twice the encoding signal
The Manchester encoding scheme is simple but useful, and can be used as one type ofpassband signal
Trang 5Fiber Optics Illustrated Dictionary
Manchester Mark IAnearly large-scale computing
machine designed and built by Fred Williams, Tom
Kilburn, and Max Newman in the late 1940s It was
significant in its ability to store programming
infor-mation The earlierproto~e for this machine was
colloquially called "Baby ' The Manchester Mark I
was composed of more than 1000 vacuum tubes
In-put and outIn-put were communicated through switches,
paper tape, and a teleprinter
mandatory access controlMAC.Innetwork
rity, an access control service that enforces a
secu-rity policy based upon a comparison of secusecu-rity
la-bels and security clearances Thus, access to resources
can be controlled based upon the sensitivity of the
desired information and the formal authorization of
entities to access information of that level of
sensi-tivity An entity with access may not on its own
en-able other entities to access a resource made
avail-able to it
Mandelbrot, Benoit(1924- ) A Polish
mathemati-cian who emigrated fIrst to France in 1936, and later
to the United States Mandelbrot extensively
re-searched areas of complex geometry which have
come to be known as fractal geometry At least part
of his thinking coincided with, or developed from,
the work ofG Julia, who published important
math-ematical observations on the iteration ofrational
func-tions in the early 1900s One family offractal images
called the Julia set is named after this predecessor
Mandelbrot's early publications on fractals include
"Les objets fractals, forme, hasard et dimension"
(1975) and "The Fractal Geometry ofNature" (1982)
which created an enormous stir, especially in North
America, and fueled much ofthe fractal imagery since
generated on computers
Certain diffraction lenses have been found to exhibit
interference patterns of a fractal nature
mandrelInproduction fabrication, a cylindrical or
tapered core or spool over which materials are pulled,
slung, or wound Mandrels may be used for
tempo-rary storage or for facilitating the dispensing ofcable
components (e.g., in a fusion splicer) See creel
MANIAC Ahistoric large-scale computer developed
in the mid-1950s by the Los Alamos National
Labo-ratory The construction of its successor, the
MA-NIAC II, inspired professors at Rice to initiate the
Rice Computer Project See Atanasoff-Berry
Com-puter, ENIAC, Rice computer
manipulation detection codeMDC Software
algo-rithms for detecting whether data or processes have
been changed or otherwise manipulated in the
in-terim, over a set period of time, or during a dynamic
session Manipulation detection code is intrinsic to
many types ofworkgroup applications in which two
or more people may be using, changing, or
interact-ing with the same application or database; the
admin-istration of the interactions must be carefully
orga-nized so they don't clobber each other's processes or
data
Manipulation detection code is also an important
as-pect of monitoring networks for intrusion or
mali-cious tampering The code may be something as
simple as a log that keeps track of logins or file changes or failed password attempts or as sophisti-cated as specific sequences of data interposed into a system, program, or file that are assessed and possi-bly manipulated to detect tampering ofvarious kinds
or to send messages to the system administrator as needed
MAPSee Media Access Project, an important orga-nization representing the public good
Marconi antennaAn antenna that requires the ground, or a large object to which it is mounted (such
as a vehicle), to aid in resonance conduction.Inother words, it is not a stand-alone antenna like a Hertz antenna Marconi antennas are commonly used in am-plitude modulation (AM) broadcasts See antenna, Hertz antenna
Marconi detectorAnadaptation of the Branly de-tector to which G Marconi added a vibrating source
to quickly set the coherer back to zero or nonconduct-ing status See detector
Marconi, Guglielmo(1874-1937) An Italian whoas
a youth demonstrated wireless telegraphy to his mother in an attic laboratory in 1894, and experi-mented with radio waves in 1895 With further sup-port and assistance from his mother, Annie Marconi, the 22-year old Marconi filed for a patent and dem-onstrated radio communications in London the fol-lowing year, and received a British patent in 1897 Marconi traveled and lectured extensively, and kept
in touch with other inventors in the field ofradio com-munications
Marconi's first communications were over very short distances, but in 1901 he showed that radio signals could be sent across the ocean between Canada and England, a distance of over 3000 km He continued for many years to devise improvements in the tech-nology, and to put them to practical application In
1909 he was awarded a Nobel prize in physics along with K Braun Marconi began broadcasting from Marconi house in 1921 under the famous 2LO call-sign See Braun, Karl Ferdinand; Murgas, Josef; Tesla, Nikola
MARECSA European maritime satellite communi-cations service established in the early 1980s; it is similar to the American MARISAT system Marine Radio Operator PermitMROP Aradiotele-phone permit issued by the Federal Communications Commission (FCC) which is required for the opera-tion of radiotelephone staopera-tions aboard certain Great Lakes vessels and for certain aviation and coastal ra-diotelephone stations TheMROPdoes not authorize the operation ofAM, FM, or television broadcast sta-tions Issuance of the 5-year, renewable permit re-quires passing the Written Element 1 exam, which covers basic radio law and operating procedures See General Radiotelephone operator license, Restricted Radiotelephone Operator Permit
Marine Safety OfficeMSO An office of the U.S Coast Guard, located in Mobile, Alabama The Coast Guard Inspection Department operates from a loca-tion near the main office The MSO is responsible for protecting life, property, and the environment along
Trang 6Guglielmo Marconi - Radio Pioneer
be linked with Global Positioning System (GPS) re-ceivers MMSI numbers were developed for compat-ibility with the public telephone system and the num-ber facilitates the routing ofdata and voice transmis-sions
If more than one radio is installed in a vessel, it is to
be programmed with the same MMSI Ifa vessel car-ries an Emergency Position-Indicating Radio Beacon (EPIRB), it may also be assigned the same MMSI as other radios on the vessel MMSI may be used for ship-to-ship and ship-to-shore communications MMSls are not exclusive to boats; INMARSAT sat-ellite terminals also use MMSI numbers
Three ofthe digits ofthe MMSI, called the Maritime Identification Digits (MIDs), indicate the country of location or registration, while six digits are used to uniquely identify the station The number may be used for emergency identification or for more mun-dane matters such as call tracking and billing
On the international level, the International Tele-communication Union (lTD) maintains a database of the MMSI of every vessel, called the Maritime Mo-bile Access and Retrieval System (MARS), which is accessible online Individual nations also maintain da-tabases In the U.S., MMSls are recorded by the Fed-eral Communications Commission (FCC) and the Coast Guard Some nations assign MMSI numbers free of charge (e.g., Industry Canada) and some charge an application fee
In spring 2001,inthe U.K., the Radiocommunica-tions Agency introduced new procedures for the is-suance ofMMSI numbers to facilitate the use ofpor-table VHF Digital Selective Calling (DSC) radio equipment Thus, vessels that cannot be installed with fixed radios can realize some ofthe benefits ofMMSI and the Global Maritime Distress and Safety System (GMDSS) through portable equipment Portable equipment is allocated unique MMSI numbers, re-gardless of the numbers assigned to existing fixed equipment associated with a vessel Portable MMSI numbers in the U.K are issued a 2359 prefix exclu-sive to mobile equipment Due to the unique nature
of portable equipment, national radio licensing au-thorities will need to be notified ifan MMSI-assigned device changes hands It is likely that other nations will institute similar policies and procedures to ac-commodate the rising number ofportable communi-cations devices
Mark acceleratorsA series ofpioneering accelera-tors leading to the development of the world-re-nowned Stanford Linear Accelerator Center (SLAC), developed by William W Hansen, who had earlier contributed to the invention ofthe Klystron tube (used
in a variety of microwave communications and
im-aging technologies) The Mark I accelerator produced
a 6 MeV electron beam The Mark IIwas used for
research in nuclear physics and the Mark IIIfor a high-energy physics program See Hansen, William Mark ISee Harvard MarkI
Mark-8Apioneer Intel8008-based personal computer kit The Mark-8, a scaled-down hobbyist cousin of
A copy ofa Western Union telegram from Marconi
to Alexander Graham Bell, thanking him for his
invi-tation to visit his summer home in Nova Scotia,
De-cember 19, 1899 In the end, Marconi declined this
ocean, so it sounds as though Marconi was
consider-ing transatlantic communications at the time, a feat
which he successfully achieved in 1901 [Library of
Congress Alexander Graham Bell Family Papers
Collection.]
111): a\"*l~ , II Yb *"*8" "
-"Ut<he'.O~ o.e ,
.t f.at"ou o1'f." hop4J "t.tt a,e SNt.ea ust It.".n :'::.-i;,
Guglielmo Marconi was a significant pioneer of
radio technologies [National Archives of Canada
Marconi Company collection.]
sippi, Alabama, and northwest Florida
MARISATMaritime Satellite First launched in
1976,MARISAT was designed to provide mobile
communications services to the U.S Navy and other
maritime clients The European MARECS system is
similar
Maritime Identification Digits(MID) See
Mari-time Mobile Service Identity
Maritime Mobile Service IdentityMMSI.An
ad-ministrative identifier allocated and issued by
vari-ous national maritime safety authorities to marine
vessels The MMSI is a unique, internationally
stan-dardized, nine-digit identification number, similar to
a radio callsign or telephone number It may be
pro-grammed by the vendor ofthe equipment or, in some
cases, the operator It is associated with a Digital
Selective Calling (DSC) number (a system that
Trang 7en-Fiber Optics Illustrated Dictionary
the PDP-8, was described in a June 1974 issue of
Radio Electronics magazine by Jonathan Titus
How-ever, it didn't achieve widespread commercial
suc-cess See Altair, Intel, Kenbak-l, Micral, Scelbi,
SIM4, Sphere System
mark-to-space transition,M-StransitionIn
teleg-raphy, the momentary change when the system
re-verses polarity, or changes from a closed to an open
circuit At this point, a small amount of delay must
be taken into consideration, which can be plotted on
a timing wave The reciprocal is the space-to-mark
transition
MARS Multicast Address Resolution Service In
ATM networking, a protocol used in IP multicasting
MAS 1 See Multi-Agent Systems Laboratory 2 See
Multiple Address System
masermicrowave amplification by stimulated
emis-sion of radiation A type of laser technology
devel-oped in the late 1950s.Aninternally-modulating
maser consists essentially of a laser light source, a
pair ofreflectors, and a modulator between the source
and one of the reflectors See laser, laser history
for a longer explanation
maskAscreen, stencil, or other object superimposed
between a surface and light, pigments, or other
me-dia put on that surface so only the unmasked portions
are seen or affected When used with light, a mask is
known as abeam block.See knife-edge focusing,
Ronchi grating
mask, dataIn computer programming, a mask is a
set ofdata, flags, or bits used as a filter or operator to
affect only those bits of data that correspond to the
mask template, or which are not included in the mask template
masquerade attackAnattack on a system by an en-tity posing as another enen-tity that has authorization to access that system or resource See spoofing, Trojan Horse, virus
mass fusion splicerMFS Amechanism for splicing multiple pairs of fiber optic filaments, typically through the application ofheat from an electrode arc This is particularly challenging as filament splicing
is a precision task and getting individual filaments
to meet production standards can be difficult In the case of mass fusion splicers, heat fusion from an arc source must be distributed evenly and quickly and in such a way that heat applied to one region offilaments does not cause side effects to those nearby Depend-ing upon how the heat is applied, the maximum num-ber offinum-bers that can be handled at a time is also lim-ited by the arc width and heat distribution technol-ogy Thus, getting even heat distribution over a wider arc and delivering it to more than a dozen fibers is a daunting precision job S Morita et al have devel-oped a custom arcing mechanism and splicer capable
of handling up to 24 fibers at a time
MFSs are commonly used to increase production lev-els and to create multiple spliced cables for assem-bly as fiber ribbons The number of fibers in a fiber ribbon continues to increase, with 24 fibers now com-mon, yet most commercial MFSs splice up to about
12 fibers, which means multiple batches are needed
to provide all the fibers necessary to assemble a wide ribbon cable See fusion splicing
Regenerative Maser
MlRROR
+- -+-eoI , "
~~-': -,
-\.
"
P01.AR12ATlOH ROTAT·OR
The basic concepts oflasers were developed into practical devices in the 1960s and 1970s This early solid-state maser design, based upon a roby laser source, was developed by A Vuylstere of General Motors Corporation in 1962-1963 A flashlamp serves as an excitation source for the pumped laser, with a pumpingfrequency ofone per cycle.
The purpose ofthis design was to make masers more efficient by decreasing the pulse width ofa laser beam while increasing power through the more concentrated beam It works by varying the regenerative condition ofthe laser s
reflective resonating chamber at specified times as a short-pulse transmission.
Many subsequent designs used the same general concept butfurther improved efficiency by modifying the interac-tion ofthe laser with the regenerative structures andprocesses within the laser cavity By the late 1970s, with demand for laser technologies growing, designs utilizing repeated optical components in theform ofchained amplifiers could provide higher-energy pulses [U.S patent #3,243,724, March 1966.J
Trang 8MMDC Intel microprocessor research and design
center located in Shrewsbury, Massachusetts In Au-
gust 2001, over 200 Compaq microprocessor
engi-neering and design employees joined Intel as part of
an agreement for Compaq Computer Corporation to
transfer key enterprise processor technology to Intel
Massie OscillaphoneAsimple type ofloose contact
electromagnetic wave detector long favored by
ama-teur experimenters and educators Two carbon blocks
(battery carbon can be used) are set up adjacent to
one another, about an inch apart, on a
nonconduct-ing base such as wood The top surfaces of the
car-bon blocks are chiseled or filed so that they have a
fine, thin edge Holes are drilled through their
sur-faces, near the base, to provide room to insert a screw
through each block, with the screwheads on the
out-side, to secure wires that connect with two binding
posts The top thin surfaces of the carbon blocks are
wiped with awoolen cloth, and a light sewing needle
or other similar conductor is laid across the top ofthe
two blocks to create a contact between them
When connected to a circuit including a battery power
source, aerial, ground, and telephone receiver, an
in-coming radio wave will interact with the
needle-car-bon contact, causing the needle to adhere more
closely to the blocks, lowering the resistance This
results in an increased flow ofcurrent which is
trans-lated into sound in the receiver Further adjustments
to the sensitivity of the needle can be made by
plac-ing a small magnet under the needle and adjustplac-ing
its height See detector
mastergroupIn analog voice phone systems, a
hier-archy for multiplexing, organized as a series of
stan-dardized increments See voice group for a chart See
jumbogroup for an illustration
Matrix.NetAcommercial service disseminating
in-formation on Internet hosts and providing Internet
Performance Measurement products Event
Adviso-ries on incidents and trends ofparticular importance
to the Internet are provided on the Web site for free
Estimates and data on Internet hosts are based on raw
data from the Network Wizards' global domain
surveys
MAU 1 See Media Access Unit 2 See Multistation
Access Unit
Mauchly, John W.(1907-1980)AnAmerican
physi-cist and engineer who collaborated with1.Eckert to
build the historic ENIAC computer See ENIAC
Maurer, Robert D.(1924- )AnAmerican scientist
and fiber optics pioneer who did graduate work at
MIT and went to work for Corning Glass Works in
1952.As head of a research team that includedD.
Keck and P Schultz, he succeeded in fabricating
op-tical fibers that could carry far more information than
existing copper wirelinks.Building on research from
a number of groups in the early 1960s, the team
de-veloped a low-loss fiber waveguide that was
practi-cal for use as a telecommunications transmission
technology
Maurer was one of the first to dope silica with
im-purities (titanium oxide) to raise the refractive index
that the light beams would reflect offthe cladding and stay within the conducting core
In 1999, Maurer was coawarded the Draper Prize for his work in fiber optics engineering and, in 2000, Maurer, Keck, and Schultz were awarded the National Medal ofTechnology for their work at Coming See Hyde, J Franklin
MAX See Media Access Exchange
Maxim, Hiram PercyFounder of the historic Ama-teur Radio Relay League (ARRL), along with Clar-ence Tuska, a young fellow radio amateur, who be-came friends with Maxim after the older radio enthu-siast had decided not to purchase radio equipment constructed by the precocious Tuska
Maximum Transfer UnitMTU In Internet Proto-col (IP) networking, the largest size of IP datagram that may be transmitted through a specific data link connection The MTU is not a fixed amount, but is a mutually-agreed value that can vary widely up to about 10 kilobytes.Ina distributed network with a number ofhops, a datagram may pass through nodes with different MTU sizes, necessitating queries and processes for handling the incoming data and its sub-sequent routing If the relay or receiving MTU is smaller than the size of a transmitted packet, the packet must be subsected to segments smaller than the MTU and information about the process conveyed
to the next link or recipient
maximum usable frequencyMUF In a radio trans-mission signal path based upon propagating radio waves through Earth's ionosphere (e.g., through the Great Circle signal path from the eastern U.S to Ja-pan), the upper frequency level that may be usable
In general, higher frequencies are associated with lower refraction rates in the ionosphere The MUF varies with terrain, region, and the influence of rays from the Sun
Software programs can monitor and calculate the various factors that influence usable radio frequen-cies and will generate and display charts that can be used to aid radio operators and listeners Since con-ditions constantly change, many software-generated maps are updated frequently, sometimes every few seconds or minutes, depending upon the system Times associated with the maps are usually expressed
in Zulu time
maxwellAnelectromagnetic unit ofmagnetic flux -the flux-per-square centimeter equal to -the magnetic induction ofone gauss, or one magnetic line offorce
Itis named after1.Clerk-Maxwell
Maxwell, James Clerk-(1831-1879)Aprecocious Scottish physicist who, building on the work ofFara-day and Bernoulli and adding ideas of his own, con-tributed many important fundamental theories and equations related to electromagnetism and the nature
of particles He also made mathematical predictions about the composition of Saturn's rings that held up well over time
Maxwell's equationsA set of fundamental math-ematical equations, originated by1.Clerk-Maxwell and further developed by Oliver Heaviside and
Trang 9Fiber Optics Illustrated Dictionary
Heinrich Hertz, for expressing radiation and
describ-ing conditions at any point under the influence of
varying electromagnetic fields These concepts and
equations are integral to many areas of science, and
are ofparticular interest in understanding and
devel-oping transmissions media, antennas, and other
ba-sic building blocks in telecommunications See
Heaviside, Oliver; Hertz, Heinrich Rudolph;
Max-well, James Clerk-
James Clerk-Maxwell- Mathematician
James Clerk-Maxwell is remembered for many of
his mathematics and physics contributions related to
fundamental laws and electromagnetism.
Maxwell's ruleEvery part of an electric circuit is
acted upon by a force which tends to move it in a
di-rection such as to enclose the maximum amount of
magnetic flux
Maxwell's theory oflightIn1860,1.Clerk-Maxwell
demonstrated that the propagation of light could be
regarded as an electromagnetic phenomenon, the
wave consisting ofan advance ofcoupled electric and
magnetic forces Ifan electric field is varied
periodi-cally, a periodically varying magnetic field is obtained
which, intum,generates a varying electrical field and
thus the disturbance is passed on in the form of a
wave Maxwell's theory predicted that the speed of
light unimpeded was constant
Maxwell's triangleAn ordered representation of
color relationships, in the shape of a triangle,
devel-oped in the late 1800s by physicistJ.Clerk-Maxwell
His premise was that this model would contain all
known colors Red, green, and blue are identified as
the three primary colors of light and are located in
the three comers of the triangle The colors
progres-sively blend until, in the center, the combination of
all the colors becomes white A system of color
no-tation was developed by laying a grid over the
tri-angle See color space, Munsell color model
Mayer, Maria Goeppert(1906-1972) A
Polish-born, American physicist who carried out
fundamen-tal research in models of the nucleus of atoms For
her independent work, she was awarded aNobel Prize
in physics, along with 1 Jensen and E Wigner
MBone, mBone multicast backbone See 6bone, backbone, multicast backbone, X-Bone
MBSSee Mobile Broadband System
MbusMessage Bus.Anopen peer-to-peer coordinat-ing infrastructure that provides integration for modu-lar computerized systems design The Mbus is espe-cially applicable to "lightweight" distributed appli-cations (e.g., limited-resource portable communica-tions devices) It enables cooperation among mod-ules serving a particular purpose while still support-ing a variety of interoperable languages and commu-nications standards The Mbus framework is exten-sible and securable and can be implemented in a va-riety of multimedia and communications environ-ments It is intended to facilitate the design and as-sembly ofcomplex systems out ofsimple components
by providing a data channel through which applica-tion modules can find one another
The Mbus is a local infrastructure providing trans-port layer functionality and addressing schemes in-cluding failure detection, session establishment and teardown, and component configuration Mbus pro-cesses are message-based rather than object-based and are not programming language paradigm-spe-cific Components can be dynamically added, re-moved, or exchanged at runtime
Mbus messaging may be unicast (to a specific ad-dress), broadcast (to all entities), or multicast (to qualified entities) The Mbus message itselfincludes
a payload consisting of commands and their associ-ated arguments/parameters that are processed by the messaged entities The entities in the system periodi-cally signal their presence to the Mbus group Message Bus profiles for local coordination and call control were submitted as Drafts to the IETF in Feb-ruary 2001 by Ott et al See MBus, Multiparty Mul-timedia Session Control http://www.mbus.org/ MCCMiscellaneous Common Carrier See Radio Common Carrier
McCahill, Mark P.Project leader in the development
of the Gopher distributed networks query/search mechanism; Gopher was released by McCahill and Paul Lindner in 1991 It was one of the first acces-sible, nontechnical software applications that enabled teachers, researchers, and other professionals un-trained in computer programming to access the store-house of information that was accumulating on com-puter networks Web search engines are, in a sense, the next generation version of Gopher for the Inter-net (text-based Gopher servers are still in use), pro-viding point-and-click and graphical capabilities in addition to the basic query/search functions that aid
in locating information online See Gopher, Web browser
McCarthy, John(1927- ) A recognized pioneer in the field ofartificial intelligence since 1955, McCar-thy was one ofthe first to promote the basic concepts
of computer timesharing in the late 1950s McCar-thy is also known as the originator of the LISP inter-preted programming language that is used to auto-mate computer-aided design processes and is popu-lar in artificial intelligence research See LISP
Trang 10cial communications services provider chaired by
Craig McCaw, which was sold to AT&T in 1994 and
renamed AT&T Wireless Services McCaw is now
collaborating with W Gates et al to develop the
Tele-desic satellite-based Internet system See TeleTele-desic
MCFSee Multimedia Communications Forum
MCIDmalicious call identification (e.g., as in ISDN
Q.81 and Q.731 number identification services)
MCNSSee Multimedia Cable Network System
MCNSIDOCSISSee Data Over Cable Service
In-terface Specification, Multimedia Cable Network
System
MCS-4A significant early (1970s) chipset that
in-spired pioneer computer designers See Intel
MCVD modifed chemical vapor deposition See
magnetron sputtering, vapor deposition
MDseriesAseries of message-digest(MD)hash
al-gorithms developed by Ronald L Rivest that can be
used, for example, to secure electronic mail
commu-nications
The MD 128-bit algorithms have been incorporated
into a number of significant data encryption systems
including RSA Security Inc cryptographic products
See Pretty Good Privacy, RSA Security Inc., RC6,
RFC 1319, RFC 1320, RFC 1321
MD Series Releases
Series Description
MD2 128-bit one-way hash developed in the
mid-1990s
MD4 128-bit one-way hash that is faster than
the previous MD4 MD4 was
incorpo-rated into P Zimmermann's Pretty Good
Privacy (PGP) 1.0
MD5 128-bit one-way hash, an improved
ver-sion ofMD4 While reasonably secure, it
has been suggested by Dobberlin that, if
two files with the same MD5 hash were
to be created (not an easy task), it might
be easier to threaten the software
Leeming has suggested that a greater
threat might be in finding two
crypto-graphic keys with the same MD5
check-sum, in which case the digital certificate
for one could be used to access the other
PGP 2.0 and subsequent versions use this
algorithm
MD-ISSee Mobile Data Intermediate System
MDS-xxxA line of commercial digital switching
products from Raytheon E-Systems
MDT mobile data terminal
MDX multidimensional extensions In the context of
the Microsoft Data Warehousing Framework, a
syn-taxfor querying multidimensional objects and data
MDX has a grammar similar to SQL
mean opinion scoreMOS Astatistical quantification
it is a value based upon people's perceived and stated impressions or preferences MOSs are useful for as-sessing sensory impressions that are difficult to mea-sure empirically, such as the quality or effectiveness
of a perfume, massage, sound, or image In audio communications, MOSs are used to determine whether a sound, such as speech, is pleasing, clear,
or intelligible In fact, the ITU-T has defined MaS more narrowly to focus on speech digitization and recreation and provides a rating scale from 1 to 5 for reporting the results This helps programmers to tweak their Voice over IP (VoIP) software, for ex-ample, to balance file sizes and transmission speeds against sound quality See P Series Recommenda-tions
mean time between failuresMTBF Aperformance indicator, the limit of the ratio of the operating time
in a device to the number of failures as the number
of failures approaches infinity At the factory, test versions of a product are often subjected to extreme use to estimate in advance what MTBF rating might
be under conditions of actual use
mechanical spliceAjoining oftwo or more wropes, wires, or fiber optic filaments by twining, pressure,
or proximity without the use of chemical or thermal bonding agents Multifiber ropes may be spliced to-gether by a number of different braiding or twining patterns to create a strong splice Wires may be spliced by bending and folding back the ends, braid-ing, or spiraling the wires about one another Both rope and wire pressure joints can be secured with tape
or other mechanical coverings without twining, but the joint is typically fragile and may pull apart even with a small amount of pressure
Fiber optic filaments may be joined by holding the carefully cleaved and aligned ends in close proxim-ity and covering them with a dust and moisture proof splice joint that prevents rotation or strain to the joint Unlike rope and wire, which may be braided and still
be useful for most normal functions, fiber filaments cannot be braided to form a joint without eliminat-ing the near-perfect end-to-end alignment that is nec-essary for maximizing light-carrying properties through the splice Splice joint assemblies are usu-ally intended for temporary fiber optic joints with fusion splicing preferred for permanent joints The choice of a mechanical or fusion splice depends upon the type ofdata that is transmitted, the amount
of pulling and motion that is exerted on the splice joint, the frequency with which the configuration is changed, and the length of the cable run Regular computer data and shorter cable runs are less subject
to loss than high-end, broadband video signals or longer cable runs and may function well with me-chanical splices Patch panels that are frequently re-configured are easier to change ifmechanical splices are used See fusion splicing
Media Access Control, Medium Access Control
MAC Functions associated with the lower halfofthe data-link layer that governs access to the available IEEE and ANSI local area network (LAN) media (or