Fiber Optics Illustrated Dictionary - Part 64 pdf

Fiber 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 magnetron, Klystron, traveling-wave tube. magnetron history Germany, 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 described the shortest waves that could be produced by vacuum tubes, in 1920. The invention of the magnetron itself is attributed to Albert W. Hull, who described 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 of velocity 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 coordination 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 magnetron; 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 development of the microwave oven for which he applied 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 generators for manufacturing applications such as surface coating (sputtering). Industrial use continues today in flat panel display manufacturing and other fabrication applications where frequency stability at a specific 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 household product by the 1980s. Magnetrons also have some novel uses in military defense. In the 1980s, the u.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 satellite communications and industrial fabrication of optical components. See magnetron sputtering. magnetron sputtering A physical vapor deposition process for coating metals, alloys, compounds, glass, and films using a coating chamber, a pump, and one 622 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 components and thin films, sputtering is an important aspect of optics fabrication. In the 1980s, Teer Coatings Ltd. developed an industrial 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 patented a sputtering process for producing thin boron- based films that have potential as ultrathin-bandpass filters and as low-radioactive elements in optical components. MAHO See mobile assisted handoff. mail bomb A vandalistic or retaliatory transmission sent through network email protocols with the intention 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, depending 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 recipients receiving thejunk email. A mail bomb rarely solves the problem, however, since recipients often retaliate. See flame wars, spam. mail distributor An agent, script, macro, or filter that takes incoming mail, evaluates the headers or other pertinent information, and distributes the mail accordingly. 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 of evaluation and processing of con- 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 discussion list. An address or database entry in the mail distributor 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 receiving it (many will boycott companies distributing commercial mail in this way). See discussion list. mail filter A software utility or feature of an email © 2003 by CRC Press LLC client, which automatically evaluates the sender, recipient, 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 individual employees' email accounts; junk email messages 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 gateway Although there are standardized protocols for the distribution of email over networks, not all systems use the same protocols, and not all protocols 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. A mail gateway is a system in a computer network that handles mail channel- ing or the resolution of protocols. mail list agent MLA. In SDNS Message Security Protocol (MSP), a mail list agent is one addressed by the message originator that represents a group of recipients. It provides message distribution services to the participants of that group on behalf of the message originator. mail list key MLK. 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 readerA software 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 readers and writers, and can be used to respond to the received messages or to compose new messages. They may also include filters to preorganize the mail before it is read, and a database interface which allows the messages to be organized and stored for later retrieval. 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 of readers. 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 capabilities. See email, USENET. mail reflector A 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 server A software system which manages incoming 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 if no valid address is found); forward mail, etc. Due to overwhelming increases in the quantity ofjunk email on the Internet, some of the newer mail servers will check the validity of the sending address, and reject the mail if the sender does not appear to be legitimate. This may result in the loss of some real email messages: for example, if someone 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 message reaches its destination. The server may reject the legitimate message. However, some consider the trade-off worthwhile, in order to deflect the thousands, or sometimes tens of thousands ofjunk mail messages that now flood the systems of most ISPs. See email.mailgateway.mail reader. mailbox The 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 destination 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 of junk email abuse - robot Web crawlers have been designed to quickly seek out mailto addresses on millions of sites, automatically adding them to junk emailing lists. See RFC 822, RFC 1738. Maiman, Theodore Harold (1927- ) An American physicist at Hughes Research laboratories who developed and patented a ruby-based laser. He described his pioneering laser research in Nature in 1960. In 1962, Maiman founded Korad Corporation to research, develop, and manufacture lasers. He eventually sold this firm to Union Carbide and formed Maiman Associates in 1968. 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 frame MOF. A central wiring connection point in a larger more complex wiring system 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 623 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary distribution frames in each department or each floor, depending upon the electrical needs and building configuration. See distribution frame. main memory In a 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 adistinction 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 considered main memory as it is not used as general-purpose storage by the system. main station This is a loosely defined phrase because it is context-specific. The people within a system often have a tacit understanding of main station facilities and the definition varies widely, depending upon the industry. 1. In telephony, 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 number, one is usually designated as the main station. 2. In computing, an "intelligent" workstation (as opposed to a "dumb" terminal, for example) installed with a full set of capabilities or which functions as a primary or secondary server. A main 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 capabilities compared to other stations in the system. A main station is not always the largest or best-equipped station 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, mini frame , and workstation are all relative. The most powerful computers in the world are called supercomputers, and the less powerful computers that are above the consumer or workstation price range are called minis or miniframes. Mainframes fall between these two categories. 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 microcomputers 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 624 (AC) power supply. In North American domestic power grids, mains power is typically single-phase power routed through a breaker box to internal wiring. Triple-phase power is also available in some areas, usually carrying higher voltages. Mains electricity 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 voltage 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 ofelectrical plugs in different countries is to prevent electrical shocks, fires, or dam- age to components resulting from the varying electrical 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 aproblem in the past, the increasing use of mains 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 electronic 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 of the National Grid mains line; sometimes it is directed into the Grid. Alternate energy sources such as wind turbines sometimes 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. An electronic diagnostic device installed at a line termination unit (LTD) ofa premises installed with telecommunications 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 L TU. Multiple MTU s may be installed along a subscriber line to further pinpoint fault locations. Major TradingArea MTA. A service area designation 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) © 2003 by CRC Press LLC from almost 500 BTAs. Regional designations are somewhat important in administering wireless services, 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 alist of counties 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). It enables the remote administration of email list subscriptions, electronic mail messages, digests, and archives. Thousands of Majordomo lists are online, many with tens of thousands of subscribers. 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 communications 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 of Unix 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 A subscriber service or feature ofa phone that causes the line to send a busy signal to an incoming call. This is like taking a line off the hook without removing the handset. While this might seem like an odd thing to do, it can actually save people money. Ifa 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). If the 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 of incoming 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- sive, obscene, or threatening intent. In many areas, 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 products or promoting them in a harassing or intention- ally deceptive manner. Upon seeking help with malicious 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 of the household or office. If the malicious call appears to involve fraud, inform the phone company, the police, relevant consumer associations, and other members of the household. Some phone companies have call investigation centers that can assist the police with trapping and tracing persistently malicious calls, especially those of a 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. A set of data modules which contain the definition ofa related set of managed object types. In SNMP management systems, it contains the logical names of informational resources on the network. In SONET network imple- mentations, objects in the Mffi are defined with a restricted subset ofAbstract Syntax Notation One (ASN.l) as to their name, syntax, and encoding. ManagementInformation Services MIS. Corporate communications professionals whose job is to facilitate the acquisition, flow, use, storage, and retrieval of information within an establishment. Mance, Henry Christopher (1840-1926) A British 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 communications for several decades. Manchester encoding An encoding scheme commonly used for baseband signaling in coaxial cable transmissions, especially 1 OBase- 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 ofabit period. A one is represented with no transition at the beginning ofa bit period. There is a tradeoff between bandwidth and binary coding, as the coding consumes part of the bandwidth. In Manchester 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 of passband signal. 625 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary Manchester Mark I An early 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 information. The earlier proto~e for this machine was colloquially called "Baby. ' The Manchester Mark I was composed of more than 1000 vacuum tubes. In- put and output were communicated through switches, paper tape, and a teleprinter. mandatory access control MAC. In network security, an access control service that enforces a security policy based upon a comparison of security 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 sensitivity. An entity with access may not on its own enable other entities to access a resource made available to it. Mandelbrot, Benoit (1924- ) APolish mathematician 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 mathematical observations on the iteration of rational functions in the early 1900s. One family of fractal 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 of Nature" (1982) which created an enormous stir, especially in North America, and fueled much of the fractal imagery since generated on computers. Certain diffraction lenses have been found to exhibit interference patterns ofafractal nature. mandrel In production fabrication, a cylindrical or tapered core or spool over which materials are pulled, slung, or wound. Mandrels may be used for temporary storage or for facilitating the dispensing of cable components (e.g., in a fusion splicer). See creel. MANIAC A historic 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 code MDC. Software algorithms 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 of workgroup applications in which two or more people may be using, changing, or interacting with the same application or database; the administration of the interactions must be carefully organized so they don't clobber each other's processes or data. Manipulation detection code is also an important aspect of monitoring networks for intrusion or malicious tampering. The code may be something as 626 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. MAP See Media Access Project, an important organization representing the public good. Marconi antenna An antenna that requires the ground, or alarge object to which it is mounted (such as avehicle), to aid in resonance conduction. In other 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 detector An adaptation of the Branly detector to which G. Marconi added a vibrating source to quickly set the coherer back to zero ornonconduct- ing status. See detector. Marconi, Guglielmo (1874-1937) An Italian who as a youth demonstrated wireless telegraphy to his mother in an attic laboratory in 1894, and experi- mented with radio waves in 1895. With further support and assistance from his mother, Annie Marconi, the 22-year old Marconi filed for a patent and demonstrated radio communications in London the following year, and received a British patent in 1897. Marconi traveled and lectured extensively, and kept in touch with other inventors in the field of radio communications. 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 ofover 3000 km. He continued for many years to devise improvements in the technology, 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 callsign. See Braun, Karl Ferdinand; Murgas, Josef; Tesla, Nikola. MARECS AEuropean maritime satellite communications service established in the early 1980s; it is similar to the American MARISAT system. MarineRadio OperatorPermit MROP. Aradiotele- phone permit issued by the Federal Communications Commission (FCC) which is required for the operation ofradiotelephone stations aboard certain Great Lakes vessels and for certain aviation and coastal radiotelephone stations. The MROP does not authorize the operation of AM, FM, or television broadcast stations. Issuance of the 5-year, renewable permit requires 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 Office MSO. An office of the U.S. Coast Guard, located in Mobile, Alabama. The Coast Guard Inspection Department operates from a location near the main office. The MSO is responsible for protecting life, property, and the environment along © 2003 by CRC Press LLC Guglielmo Marconi - Radio Pioneer abIes group or broadcast calling). DSC radios may be linked with Global Positioning System (GPS) re- ceivers. MMSI numbers were developed for compat- ibility with the public telephone system and the number facilitates the routing of data and voice transmissions. 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 satellite terminals also use MMSI numbers. Three of the digits of the 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, in the U.K., the Radiocommunica- tions Agency introduced new procedures for the issuance ofMMSI numbers to facilitate the use of portable VHF Digital Selective Calling (DSC) radio equipment. Thus, vessels that cannot be installed with fixed radios can realize some of the 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 exclusive to mobile equipment. Due to the unique nature of portable equipment, national radio licensing authorities will need to be notified if an MMSI-assigned device changes hands. It is likely that other nations will institute similar policies and procedures to ac- commodate the rising number of portable communications devices. Mark accelerators A series of pioneering accelerators 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 of the 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 II was used for research in nuclear physics and the Mark III for a high-energy physics program. See Hansen, William. Mark I See Harvard Mark I. Mark-8A pioneer Intel8008-based personal computer kit. The Mark-8, a scaled-down hobbyist cousin of A copy of a 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 particular visit because Bell slocation was noton the ocean, so it sounds as though Marconi was consider- ing transatlantic communications at the time, afeat which he successfully achieved in 1901. [Library of Congress Alexander Graham Bell Family Papers Collection.] 111): a\ "* l~ ,. II Yb *"*8" " ::.~;: 19_,! J ~~, ~ , "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.] the coastlines and navigable waterways of Missis- sippi, Alabama, and northwest Florida. MARISAT Maritime 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 Identity MMSI. An ad- ministrative identifier allocated and issued by various national maritime safety authorities to marine vessels. The MMSI is a unique, internationally standardized, nine-digit identification number, similar to a radio callsign or telephone number. It may be programmed by the vendor of the equipment or, in some cases, the operator. It is associated with a Digital Selective Calling (DSC) number (a system that en- 627 © 2003 by CRC Press LLC 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-S transition In telegraphy, 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. maser microwave amplification by stimulated emis- sion of radiation. A type oflaser technology developed in the late 1950s. An internally-modulating maser consists essentially of a laser light source, a pair of reflectors, and a modulator between the source and one of the reflectors. See laser, laser history for a longer explanation. maskA screen, stencil, or other object superimposed between a surface and light, pigments, or other media put on that surface so only the unmasked portions are seen or affected. When used with light, a mask is known as a beam block. See knife-edge focusing, Ronchi grating. mask, data In computer programming, a mask is a set of data, 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 attackAn attack on a system by an entity posing as another entity that has authorization to access that system or resource. See spoofing, Trojan Horse, virus. mass fusion splicer MFS. A mechanism for splicing multiple pairs of fiber optic filaments, typically through the application of heat 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 of filaments does not cause side effects to those nearby. Depend- ing upon how the heat is applied, the maximum number of fibers that can be handled at a time is also limited by the arc width and heat distribution technology. 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 developed a custom arcing mechanism and splicer capable of handling up to 24 fibers at a time. MFSs are commonly used to increase production levels 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 common, 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 alREFRINGENT • [HIGH POWER POLAFUZATIOH SELECTOR 8EAM MlRROR +- -+-eoI , " ~~-': ,. \. " P01.AR12ATlOH ROTAT·OR The basic concepts of lasers 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. Aflashlamp serves as an excitation source for the pumped laser, with a pumping frequency of one per cycle. The purpose of this design was to make masers more efficient by decreasing thepulse width of a laser beam while increasingpower through the more concentrated beam. It works by varying the regenerative condition of the lasers reflective resonating chamber at specified times as a short-pulse transmission. Many subsequentdesigns usedthe samegeneral concept butfurther improved efficiency by modifying the interac- tion of the laserwith the regenerativestructures and processes within the laser cavity. By the late 1970s, with demand for laser technologies growing, designs utilizingrepeatedoptical components in theform of chainedamplifiers could provide higher-energypulses. [U.S. patent #3,243,724, March 1966.J 628 © 2003 by CRC Press LLC Massachusetts Microprocessor Design Center MMDC. An Intel microprocessor research and design center located in Shrewsbury, Massachusetts. In Au- . gust 2001, over 200 Compaq microprocessor engineering and design employees joined Intel as part of an agreement for Compaq Computer Corporation to transfer key enterprise processor technology to Intel. Massie OscillaphoneA simple type of loose contact electromagnetic wave detector long favored by amateur 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 carbon blocks are chiseled or filed so that they have a fine, thin edge. Holes are drilled through their surfaces, 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 a woolen cloth, and a light sewing needle or other similar conductor is laid across the top of the two blocks to create a contact between them. When connected to a circuit including a battery power source, aerial, ground, and telephone receiver, an incoming radio wave will interact with the needle-carbon contact, causing the needle to adhere more closely to the blocks, lowering the resistance. This results in an increased flow of current 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 adjusting its height. See detector. mastergroup In analog voice phone systems, a hier- archy for multiplexing, organized as a series of standardized increments. See voice group for a chart. See jumbogroup for an illustration. Matrix.NetA commercial service disseminating information 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)An American physicist and engineer who collaborated with 1. Eckert to build the historic ENIAC computer. See ENIAC. Maurer, Robert D. (1924- )An American 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 included D. Keck and P. Schultz, he succeeded in fabricating optical fibers that could carry far more information than existing copper wire links. Building on research from a number of groups in the early 1960s, the team developed a low-loss fiber waveguide that was practical 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 of the conducting core above that of the cladding so that the light beams would reflect off the 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 of Technology for their work at Coming. See Hyde, J. Franklin. MAX See Media Access Exchange. Maxim, Hiram Percy Founder of the historic Ama- teur Radio Relay League (ARRL), along with Clar- ence Tuska, a young fellow radio amateur, who became friends with Maxim after the older radio enthu- siast had decided not to purchase radio equipment constructed by the precocious Tuska. Maximum Transfer Unit MTU. 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. In a distributed network with a number of hops, a datagram may pass through nodes with different MTU sizes, necessitating queries and processes for handling the incoming data and its subsequent 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 frequency MUF. In a radio transmission 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 frequencies and will generate and display charts that can be used to aid radio operators and listeners. Since conditions 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. maxwellAn electromagnetic unit of magnetic flux - the flux-per-square centimeter equal to the magnetic induction of one gauss, or one magnetic line offorce. It is named after 1. Clerk-Maxwell. Maxwell, James Clerk- (1831-1879) A precocious Scottish physicist who, building on the work ofF ara- day and Bernoulli and adding ideas of his own, contributed many important fundamental theories and equations related to electromagnetism and the nature of particles. He also made mathematical predictions about the composition ofSaturn's rings that held up well over time. Maxwell's equations A set of fundamental mathematical equations, originated by 1. Clerk-Maxwell and further developed by Oliver Heaviside and 629 © 2003 by CRC Press LLC Fiber 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 developing transmissions media, antennas, and other basic 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 andphysics contributions related to fundamental laws and electromagnetism. Maxwell's rule Every 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 oflightIn 1860, 1. Clerk-Maxwell demonstrated that the propagation oflight could be regarded as an electromagnetic phenomenon, the wave consisting of an advance of coupled electric and magnetic forces. If an electric field is varied periodically, a periodically varying magnetic field is obtained which, in tum, 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 triangle An ordered representation of color relationships, in the shape ofa triangle, developed in the late 1800s by physicist J. Clerk-Maxwell. His premise was that this model would contain all known colors. Red, green, and blue are identified as the three primary colors oflight 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 ofcolor notation was developed by laying a grid over the triangle. See color space, Munsell color model. Mayer, Maria Goeppert (1906-1972) A Polish- born, American physicist who carried out fundamental research in models of the nucleus of atoms. For her independent work, she was awarded aN obel Prize in physics, along with 1. Jensen and E. Wigner. 630 MBone, mBone multicast backbone. See 6bone, backbone, multicast backbone, X-Bone. MBS See Mobile Broadband System. Mbus Message Bus. An open peer-to-peer coordinat- ing infrastructure that provides integration for modu- lar computerized systems design. The Mbus is especially applicable to "lightweight" distributed applications (e.g., limited-resource portable communications devices). It enables cooperation among modules serving a particularpurpose while still support- ing avariety ofinteroperable languages and communications standards. The Mbus framework is exten- sible and securable and can be implemented in a variety of multimedia and communications environ- ments. It is intended to facilitate the design and as- sembly of complex systems out of simple components by providing a data channel through which application modules can find one another. The Mbus is a local infrastructure providing trans- port layer functionality and addressing schemes including failure detection, session establishment and teardown, and component configuration. Mbus processes are message-based rather than object-based and are not programming language paradigm-specific. Components can be dynamically added, re- moved, or exchanged at runtime. Mbus messaging may be unicast (to a specific address), broadcast (to all entities), or multicast (to qualified entities). The Mbus message itself includes a payload consisting of commands and their associated arguments/parameters that are processed by the messaged entities. The entities in the system periodically 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/ MCC Miscellaneous 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 accessible, nontechnical software applications that enabled teachers, researchers, and other professionals un- trained in computer programming to access the store- house ofinformation that was accumulating on computer 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), providing 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- ) Arecognized pioneer in the field ofartificial intelligence since 1955, McCar- thy was one of the first to promote the basic concepts ofcomputer 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 popular in artificial intelligence research. See LISP. © 2003 by CRC Press LLC McCawCellularCommunications,Inc.A commercial 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 Teledesic. MCF See Multimedia Communications Forum. MCID malicious call identification (e.g., as in ISDN Q.81 and Q.731 number identification services). MCNS See Multimedia Cable Network System. MCNSIDOCSIS See Data Over Cable Service In- terface Specification, Multimedia Cable Network System. MCS-4 A significant early (1970s) chipset that inspired pioneer computer designers. See Intel. MCVD modi fed chemical vapor deposition. See magnetron sputtering, vapor deposition. MD seriesA series of message-digest (MD) hash algorithms developed by Ronald L. Rivest that can be used, for example, to secure electronic mail communications. The MD 1 28-bit algorithms have been incorporated into a number ofsignificant 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 incorporated into P. Zimmermann's Pretty Good Privacy (PGP) 1.0. MD5 128-bit one-way hash, an improved version 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 cryptographic 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-IS See Mobile Data Intermediate System. MDS-xxx A 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 syntax for querying multidimensional objects and data. MDX has a grammar similar to SQL. mean opinion score MOS. A statistical quantification of reported subjective impressions. In other words, 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 example, to balance file sizes and transmission speeds against sound quality. See P Series Recommenda- tions. mean time between failures MTBF. A performance 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 ofa product are often subjected to extreme use to estimate in advance what MTBF rating might be under conditions of actual use. mechanical spliceAjoining of two 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, braiding, 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 proximity 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 ajoint without eliminat- ing the near-perfect end-to-end alignment that is necessary for maximizing light-carrying properties through the splice. Splice joint assemblies are usually intended for temporary fiber optic joints with fusion splicing preferred for permanent joints. The choice ofa mechanical or fusion splice depends upon the type of data that is transmitted, the amount ofpulling 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 mechanical splices. Patch panels that are frequently re- configured are easier to change if mechanical splices are used. See fusion splicing. Media Access Control, Medium Access Control MAC. Functions associated with the lower halfof the data-link layer that governs access to the available IEEE and ANSI local area network (LAN) media (or 631 © 2003 by CRC Press LLC . Fiber 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 magnetron, Klystron, traveling-wave tube. magnetron history Germany, 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 described the shortest waves that could be produced by vacuum tubes, in 1920. The invention of the magnetron itself is attributed to Albert W. Hull, who described it publicly in the AlEE Journal, in 1921. Au- gust Zacek may have made similar discoveries in the early 1920s, as he ordered. Digital Selective Calling (DSC) number (a system that en- 627 © 2003 by CRC Press LLC 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,. LLC 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-S transition In telegraphy, 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