Fiber Optics Illustrated Dictionary - Part 98 pptx

Fiber Optics Illustrated Dictionary indicating a direction only, having a length (magnitude) of one (1 - unity). lUI = 1. Thus, a vector may be converted to a unit vector by dividing each component of the vector by its magnitude. See vector. United States Geological Survey USGS. The USGS carries out fundamental and applied research in geological surveying, cartographic data collection, storage, search, retrieval, and manipulation. It is respon- sible for assessing natural ecological events, energy, land, water, and mineral researches. The USGS con- ducts the National Mapping Program, and publishes thousands of reports and maps each year. United States Telephone Association, United States Telecom Association USTA. An organization founded in the 1800s which promotes the well-being of the industry, and provides technical and standards assistance, discussion forums, and publications for its members. USTA represents more than 1200 local exchange carriers (LECs). USTA provides representation before Congress and various regulatory bodies, training courses, technical bulletins, conferences, and media relations. USTA arose from the National Telephone Associa- tion, established in 1897. This organizational strength provided a voice for independents in the dominant Bell marketplace. The National Telephone Associa- tion later became the United States Independent Tele- phone Association (USITA). The Kingsbury Commit- ment, an important step toward cooperation between Bell and the Independents, entered into in 1913, may have averted government takeover of the telephone industry arising from charges of the monopolistic control exerted by Bell at that time. After the mid-I 980s divestiture of AT&T, USITA became the United States Telephone Association (USTA) and it is now known as the United States Telecom Association to reflect the broader technology base of local exchange carriers (LECs). http://www.usta.org! United Telephone Company Ahistoric phone company founded in 1898 by Cleyson 1. Brown in Abilene, Kansas, and later expanded to other com- munities.It operated there until 1966, and then moved to Shawnee Mission, Kansas, where it forms the local division of Sprint Corporation. See Museum of Independent Telephony. UNIVAC Universal Automatic Computer. A historic, large, general-purpose electronic computing system in active use in the 1950s, descended from the ENIAC.It was designed and built in the mid-1940s by the Eckert-Mauchly Electronic Control Corpora- tion, but taken over before its completion by Reming- ton-Rand. UNIVAC was advertised as the UNIVAC File-Computer "electronic brain" by Remington Rand Univac, a Division of Sperry Rand Corpora- tion. UNIVAC was the first significant commercial nonmilitary computing system, available for a little more than $1 million. A mercury delay line, incorporating a long tube of mercury, was installed inside the computer housing as a memory device. There were a number of input! output modes, including magnetic tape, and various 962 peripherals, such as printers. The clock speed of a UNIVAC wasn't much different from the personal computers first introduced in the mid-1970s and it took a great deal of care and expertise to get the system up and running and to maintain the vacuum tube- based hardware. It was programmed wi th X-I. In spring, 1951, the U.S. Census Bureau acquired an 8-ton UNIVAC system. In 1952, the UNIVAC was used to (correctly) predict the presidential election returns but the results were not made public until after the election. Due to the media exposure, UNIVAC became so well known that the name became a ge- neric tenn for large computing devices. There is an original UNIVAC in the Smithsonian museum. See ENlAC. Universal ADSL Working Group UAWG. A commercial consortium fonned to promote an easy-to- deploy, fast version of Digital Subscriber Line (xDSL) based on ANSI TI.413. Since traditional ADSL installations require a splitter to be wired to the subscribers' premises and a custom modem installed in their computer, there have been a number ofinitiatives to simplify the installation process and, hence, the cost, and to allow the subscribers achoice of modem hardware. See G.lite. universal asynchronous receiver-transmitter UART. UART chips and UART circuitry perform a conversion function within a computer. When a computer software program generates data that travels from the computer to the serial card in a peripheral slot, or through a serial device to an external modem, the parallel data generated by the computer are converted by the UART into serial data that are then transmitted through the modem. The same process occurs in reverse at the receiving end. This is /lot the same process as is performed by a pair ofconnected modems, which modulate and demodulate a signal, convert it from digital to analog to transmit through the phone line and from analog to digital when received. The UART does its job before modulation! demodulation occurs in the modem. A UART chip may be in the computer, or in the modem itself. Universal Call Model UCM.In telecommunications SS7 routing, an extension of the Basic Call Model associated with Intelligent Networks (INs). The UCM provides mediation between the Originating Call Model (OCM) and the Terminating Call Model (TCM). The UCM receives responses from an initial address message (lAM) and its associated calling line ID, whereupon the UCM activates seizure of the originating channel. It then puts out a request for analysis of the A- and B-number and route and, when the information is received, looks up the dialed number in a dialing base for routing. During the call, the UCM maintains routing and bearer circuit status. In systems using PRlISDN, the UCM is bypassed. Also called line concentration module. See Intelligent Networks Call Model, Virtual Switch Controller. Universal Digital Loop Carrier UDLC. Digital public switched network (PSN) carrier systems comprising a central office (CO) terminal near the switching system, a remote terminal at the customer's © 2003 by CRC Press LLC premises, and a digital transmission link connecting the two. Functional criteria for digital loop carrier systems are described in Bellcore TR-NWT-000057. Digital switching streamlined the system, enabling central office terminals to be integrated into the digital switch. UDLCs were introduced in North America in the early 1970s. Connections to analog interfaces are through twisted-pair copper wires, as are those between the remote terminal and the network interfaces. Universal Encoding Conversion Technology UECT. A Digital Equipment Corporation (DEC) pro- prietary software system for converting documents to and from Unicode. UECT has been incorporated into the AltaVista search engine, one of the significant search tools on the Web from Digital Equipment Corporation. universal mailbox A centralized computer point of access for a variety of types ofmessages, including email, digitally encoded voice messages, facsimiles, etc., so the user can look at one listing to determine what to read and when to read it and to simplify the filing and cross-management of document databases. See integrated messaging. Universal Mobile Telecommunications Systems UMTS. In conjunction with general packet radio service (GPRS), UMTS encompasses next-generation wireless telecommunications technologies. UMTS is a broadband, packet-based data transmissions technology base supported in Europe and also potentially in Japan and other Asian countries. It is not directly compatible with emerging American mobile standards. UMTS technologies are characterized by high mo- bility and flexibility in terms of available data rates and are considered suitable for wireless Internet access with global roaming capabilities. Since wireless data technologies have lagged somewhat over the years from lack of support and interoperability, UMTS standards were developed to improve the situation and encourage market support for UMTS deployment. UMTS standards were developed by two groups of prominent telecommunications vendors. Trials of UMTS were carried out by Nortel Networks and Brit- ish Telecom (BT) in 1999. In 2000, ETSI finalized the first series of3GPP specifications into the UMTS standard. The UMTS first series specifies a wide variety of services, including radio access, functions for applications development, multimedia messaging, and much more. The Release 99 first series enables developers to move ahead with the rollout of3G services. As a result of standardization, companies such as Nortel Networks have entered into agreements with developers to create 3G wireless dual-mode modems supporting the UMTS standard. Universal Mobile Telecommunications Systems Initiatives UMTS Initiatives. Third-generation mobile telephony research and deployment efforts that are being carried out by a number ofcompanies in a variety of regions, but particularly in Western Europe. UMTS initiatives seek to support and foster the establishment of broadbased UMTS standard-based wireless communications systems: In May 2000, Lucent announced an initiative to create a Bell Laboratories Research & De- velopment Centre to partner with Italian uni- versities to enable startup businesses and re- searchers to test ideas and products related to UMTS integration an implementation. • In November 2000, the German Bundestag (Parliament) approved UMTS funding for education and research to promote future development ofUMTS technologies. • In September 2001, Europolitan Vodafone announced costs for their UMTS initiative in Sweden and a collaboration agreement with the Vodaphone Group. Universal Naming Convention UNC. 1. In general, a convention for logically mapping a name to a process or device such that its explicit file path or routing path is transparent to the user. The UNC can be used to set up a virtual network with various printers, storage devices, scanners, etc. linked in as resources regardless of where they may be located on the network. 2. In terms of file storage, a convention for identifying a shared file on a computer network without explicitly identifying its storage location to the user. This increases ease of access and transpar- ency to users who shouldn't have to worry about the location of a file on a virtual storage system (which may be a device on another machine a few feet or a few thousand miles away) except as desired. Universal Payment Preamble UPP. An electronic commerce payment mechanism developed by JEPI, based on work by Don Eastlake. The mechanism was described through an RFC document including sev- eral examples in August 1996 as to its relationship between the HTTP Payment Extension Protocol (PEP). UPP provides auniform vocabulary for a uniform syntax and naming options common to payment systems. Common parameters could be specified within PEP-specified header fields and in payment- system-specific headers. See JEPI, Payment Exten- sion Protocol. universal payphoneApayphone with a wide scope of payment options including coin, calling card, credit card, collect, etc. Universal Serial Bus USB. An open serial data bus standard developed by a consortium of prominent computer products and telecommunications services providers in the mid-1990s. It allows peripherals to be attached to a computer through a single peripheral attached to the motherboard, with other devices chaining or attached in a star topology. Commercial USBs are designed to support many devices, sometimes up to 64 (the host computer is considered a device). A USB will sometimes also provide additional power to devices that might require it. One of the basic goals of USB development was ease of use. It was intended for personal computer users to be able to easily attach and detach external computer 963 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary peripherals without a lot of technical expertise. Thus, characteristics such as hot swapping and the capability to attach multiple devices were desirable design goals. Through a process of enumeration, peripherals are assigned unique addresses for managing runtime data transmissions and transactions. The Human Interface Device (HID) Class is a USB Core-compliant aspect of USB intended for user input devices that require relatively slow data rates (1.5 MBytes/sec) compared to high-speed storage access, audio/visual, or networking transmissions (12 MBytes/sec). RIDs include keyboards, mice, joysticks, graphics tablets, etc. Traditionally the USB RID Class is connected to the computer through a wire, but interest in wireless versions is strong and implementations are being suggested. The format is rapidly gaining popularity and many personal computers now come with USB ports built in. Older computers with PCI slots can be adapted for use with USB through peripheral cards. It is common for a peripheral card to have two USB ports. With the success of USB 1.1, work continued on USB 2.0 to give it even better performance characteristics. It is estimated that higher data rates of more than 400 MBytes/sec may be possible without substantial hardware changes (with the exception of hubs) through the use of micro frames. Transmission speeds for a variety of attached devices would be individually negotiated, providing backward compatibility and flexibility in device data rates. See FireWire. Universal Service Order Code USOc. An identification system for tariff services and equipment introduced in the 1970s by AT&T, and later adopted by the Federal Communications Commission (FCC). Since divestiture, the code is even less universal than before, with individual Bell operating companies developing billing systems somewhat independently of one another. Universal Time See Coordinated Universal Time. Universal Transverse Mercator projection UTM. A map projection technique that preserves angular relationships and scale. UTMs are used in many plani- metric and topographic maps. A UTM consists of a series of identical projections, each 6° of longitude oriented to a meridian, taken from around the world's mid-latitudes. Universal Unique Identifier UUID. Aunique identifier originating from the Network Computing Sys- tem (NCS) and the Open Software Foundation (OSF) distributed computing environment. In February 1998, Leach and Salz defined the format ofUUIDs guaranteed or extremely likely to be different from all UUIDs generated until the year 3400 A.D., de- pending upon the mechanism chosen for generating theUUID. In a data communications equipment (DC E) transmissions cell, it is a broadly unique 128-bit identifier assigned to an object. The UUID is typically used in global contexts where it is a challenge to assign a guaranteed unique ID. Thus, a combination of data are combined to produce the UUID, which may include time stamps, random quantities (or seeds for 964 random quantities), and the hardware address of the originating network device, etc. In the context ofUniversal Resource Identifier (URI) schemes on the Internet, a UUID enables network resources to be uniquely named without regard to location; they are thus not tied to aphysical root name- space. These are also known as Globally Unique Iden- tifiers (GUIDs). UUIDs are useful in that they need not be assigned and administered by a centralized authority (beyond node identifiers), as are domain names. They also have potential as transaction IDs, aproperty ofparticular interest to e-commerce transactions. In Unix applications, the Uuid class provides a means for creating and converting Uuid objects to support network UUIDs. Universal Wireless Communications UWC. A wireless communications collaborative program initiated by wireless operators and vendors in 1995. The program is built on the TIA IS-136 Time Division Multiple Access (TDMA) radio frequency standards, along with IS-41 Wireless Intelligent Network (WIN) standards. Universal Wireless Communications Consortium UWCC. A Washington State LLC, established to support carriers and vendors ofIS-136 TDMA/IS-41 WIN standards. The UWCC sponsors a number of working forums, including the Global TDMAForum (GTF), the Global WIN Forum (GWF), and the Glo- bal Operators Forum (GOF). See Universal Wireless Communications. http://www.uwcc.org/ Unix A widespread, powerful operating system, originally developed in 1969 by Ken Thompson at AT&T Bell Laboratories. The trademarked version ofUnix is spelled all in caps as UNIX, whereas Unix spelled in upper and lower case is used generically in the computer industry to refer to the many freely distrib- utable flavors of Unix that have been implemented by different groups. UNIX has gone through anum- ber of hands, from AT&T, to Novell Inc., to the X/ Open Company Limited. See UNIX. UNIX UNIX is a powerful, widespread, cross-plat- form, Internet-friendly, multitasking, multiuser operating system. When spelled in all capitals, UNIX is a registered trademark, licensed exclusively through the X/Open Company Limited. See Single UNIX Specification, Unix. UNIX Computing Forum UCF. A comments and feedback forum through the Santa Cruz Operation, Inc. (SCO), which provides UNIX server operating systems and related products. Unlicensed Personal Communications Services, Unlicensed PCS UPCS. A number of low-range communications systems can be used without broadcast licensing. These are commonly used for applications such as cordless phones, intercoms, monitors, etc. Some are incorporated into short-range wireless local area network (LAN) data and phone systems. Specific frequency ranges have been assigned to UPCS services by the Federal Communications System (FCC). UPCS are permitted within the 1890 to 1930 MHz frequency ranges and are further © 2003 by CRC Press LLC subdivided for use with asynchronous (1910 to 1920 MHz) and isochronous (1890 to 1910 and 1920 to 1930 MHz) communications. See band allocations. unlisted phone number A service requiring a fee, in which a phone listing is not published in printed directories or available through directory assistance. Some carriers also provide unpublished service, which is excluded from printed directories, but may be listed with directory assistance, as a partial privacy measure. People pay to prevent their numbers from being listed for a variety of reasons: to avoid crank calls, undesired telephone solicitations, harassment from ex-spouses, etc. Some carriers make it possible for callers to leave a message for an unlisted number, which the caller mayor may not return at his or her option. This is useful for emergency calls. See unpublished phone number. unmatched call A call that does not have a corre- sponding match in a Service User Table (sur). Call matching is a way ofdetermining whether the call is authorized and should be penni tted to ring through. If there is no match to the destination number in any of the relevant lookup tables, such as the Authoriza- tion Code Table (ACT) or Calling Card Table, the card will likely be rejected or may be redirected to someone in authority. unpublished phone number A service, usually requiring a fee, in which a phone listing is not published in printed directories, but mayor may not (depend- ing upon the carrier) be available through directory assistance. Thus, iflisted with directory assistance, it is a midway solution between a listed and an unlisted number. Some people choose unpublished phone numbers to avoid crank calls and undesired telephone solicitations. Some carriers will subscribers to exclude addresses from a published listing, without charging extra. For further privacy, see unlisted phone number. unshielded Unprotected from emitting or receiving electromagnetic interference or broadcast signal interference. Most cables are shielded with plastic and! or metal foil, but since this increases the weight and cost of the cable, there are still circumstances where low shielded or unshielded cables are used. In video applications, well-shielded cables are recommended. Monitors should be shielded to protect users from radiation exposure, and computers shielded to prevent interference with nearby broadcast devices, such as radios. Improper or insufficient shielding may result in Federal Communications Commission (FCC) rejection in the manufacture of new products. unshielded twisted-pair UTP. A very common type of cable consisting of one or more pairs oftwisted copper wires bound together. UTP is frequently used for phone wire installations intended to carry faster data rates. See twisted-pair cable. Unsolicited Commercial Electronic Mail Act of 2001. A bill proposed by Rep. Heather Wilson in Feb- ruary 2001 to protect Internet users and providers from unsolicited and unwanted electronic mail. Between 1995 and the present, the volume and frequency ofunsolicited electronic mail, also known as "spam," rose dramatically, resulting in significant load to service providers along with lost productiv- ity and undesired costs to users who had to filter out the messages and sift through them to locate legitimate mail. Because the cost to the sender of sending email is often insignificant, "junk" email is a far greater problem than junk postal mail. The cost of sending out amillionjunkpostal solicitations is typically more than $30,000, providing an economic de- terrent to excessive mailings. In contrast, the cost of sending out a million email messages may only cost pennies to the sender but may result in significant forwarding, storing, and filtering costs to service providers and recipients, especially as junk email file sizes increase due to added images and HTML-format tags. Junk email is now widely used to promote fraudu- lent money-making schemes, off-shore sheltering of illegal gains, young teen pornography, black market pharmaceuticals, and gray market consumer items. Thus, many feel that stronger legislative constraints on unsolicited electronic mail should be put in place to protect recipients and providers from bearing the cost and inconvenience of these solicitations. unspecified bit rate UBR. An unguaranteed ATM networking service type in which the network makes abest-effort attempt to meet the sender's bandwidth requirements. See available bit rate, cell rate. unsupervised transfer,blind transferA phone call transfer in which the recipient is not advised as to the identity of the caller. This is common on automated systems in which the caller can select an extension by way of the keypad on a touchtone phone. unused Aproduct which may have been opened, or taken home and returned, but which has not been used. It may have slight abrasions and, if sold, may carry a warranty that differs from a new warranty. UPC Usage Parameter Control. A network mechanism for monitoring and controlling traffic and guar- anteeing service for legitimate uses. See traffic po- licing, traffic shaping. UPCS See Unlicensed Personal Communications Services, Unlicensed PCS. UPGRADE An ACTS project intended to increase the capacity of the existing single fiber European Communications network to higher bit rates over existing hardware to serve the needs of future communications. Capacity will in part be increased with new modulators, switches, and semiconductor laser amplifiers. Various European networks (Deutsche Telekom, 1998 EXPO in Spain, etc.) are involved in testing the systems. Test results and components from the project will be used to update single fiber links to ca. 1300-nm wavelength. See BLISS, BROAD- BAND, and WOTAN. uplink In broadcast communications, the uplink is the leg from an Earth station to a satellite. From the satellite back to the Earth is a downlink. The dis- tinction is made partly because of the different technologies used in satellite and Earth stations, but also because uplink and downlink services can often be purchased separately. 965 © 2003 by CRC Press LLC Fiber Optics Illustrated DictionanJ upload, send, transfer To transmit a broadcast or transfer data from the current device to another one, usually at a different location or desk. Computer data are often uploaded from a personal computer to the Internet or to a mainframe. Information from a lap- top may be uploaded to a desk computer. Telecom- munications software, Web browsers, and FTP are common ways in which people upload files. Broad- casts may be uploaded to a satellite link. See upstream. Contrast with download. Ground-Air Data Transfer The uplink is the transmissions path fiom the Earth to the satellite, which is often at a differentfrequency from the downlink in order to reduce ill/erference between incoming and outgoing signals. upp See Universal Payment Preamble. upper layer protocol ULP. In hierarchical network models, a protocol that operates at a higher level of the model, which usually consists of appl ication and user transactional functions. In the Open Systems Interconnection (OSI) reference model, ULP more speci fically refers to protocols in any of the layers higher than the layer currently being referenced, although colloquially it often means the next higher layer. upper memory area UMA. Asection of memory on Intel-based IBM and licensed third-party computers commonly used to buffer video data which can be ac- cessed and read by a video graphics display card. upstream Generally, the transmission going in a direction away from the reference point. Thus, the stream of data from a personal computer to a mainframe would be considered upstream. Sometimes the designation implies from a smaller or less powerful system to a larger or more powerful system, so its use is not completely standardized. In cable networks, the transmission from the transmitting station to the cable television headend is the upstream direction. See upload. Contrast with downstream. uptime An uninterrupted interval during which a system or process has been in active service. The active, functional time between failure or maintenance pe- riods. Contrast with downtime. upwardly compatible A device or program intended to work with later upgrades or revisions. Upwardly 966 compatible may also mean compatible with a larger or more complex version. For example, a handheld device bar code device may be designed to be upwardly compatible with a desktop computer. Upward compatibility in terms oflater versions is much more difficult to achieve than downward compatibility, since future changes or improvements cannot always be anticipated. Contrast with downwardly compatible. URA See Uniform Resource Agent. URI See Uniform Resource Identifier, URL, URN, RFC 1630, RFC 1738, RFC 1808. URL See Uniform Resource Locators. See RFC 1738. URN Uniform Resource Name. See RFC 1737. U.S. West One of the regional companies created when AT&T was divested in the mid-l 980s, comprising Mountain Telephone, Pacific Northwest Bell, Northwestern Bell, and other related firms servicing the "Fourth Comer." USB See Universal Serial Bus. USDC U.S. Digital Cellular. A telephone standard which uses frequency division multiple access (FDMA) and time division multiple access (TDMA) techniques in the 824 to 894 MHz range. USDLA United States Distance Learning Associa- tion. See distance learning. USDN U.S. ISDN services. See ISDN. used A term describing a product that has been opened and used, with no implications as to the quality, age, or remaining useful life of the product. Used equipment is generally represented as being in working condition, as far as is known. See certified, fair, like new, refurbished. USENET Created in late 1979, shortly after the release ofa Unix V7 which supported UUCP, USENET is an important communications medium best known for its more than 35,000 public newsgroups. USENET was developed by Tom Truscott and Jim Ellis at Duke University, and Steve Bellovin at the University of North Carolina. The first two-site installation was described in January 1980, at the Usenix conference and, after modifications by Steve Daniel and Tom Truscott, it became known as A News. As soon as it caught on, A News volume began to steadily increase. In 1981 Mark Horton, from UC Berkeley, and Matt Glickman enhanced the software to better handle the increasing volume of information. This 1982 version was known as B News. Two years later, administration of the software was taken over by Rick Adams from the Center for Seis- mic Studies. Moderated groups capability was added, in addition to compression, a new naming structure, and control messages. A rewrite by Geoff Collyer and Henry Spencer of the University of Toronto was released as C News in 1987. In 1992, Rich Salz released lnterNetNews (INN), a program optimized for NNTP hosts, but with support for UUCP. INN was designed for socket-oriented Unix hosts. Enhancements and bug fixes to INN were released by David Barr, beginning in 1995. Maintenance of INN was taken over by the Internet © 2003 by CRC Press LLC Software Consortium. UUCP gave way to TCP/IP, and TCP/IP's greater compatibility across platforms was a means to provide wider access to newsgroups. The Network News Transfer Protocol (NNTP) was also developed and, in 1986, a means to use this for news articles was released. For more information, see the "USENET Soft- ware: History and Sources FAQ" on the Internet. See FidoNet, newsgroup, RFC 822, RFC 1123, RFC 977, RFC I036,RFC 1153. user Sometimes called end were Although often used to indicate a nontechnical consumer ofa product or service, a user also generically refers to anyone in- teracting with that product or service, as opposed to developing or distributing it. user acceptance testing, user application testing UAT. The testing ofa product by actual users (those who fit the profile ofpotential buyers or users) in conditions similar to what the use environment would be in order to ensure acceptance of the product and sufficient design ergonomics and explanation (menus, manuals, etc.) for the operator to be able to use the product without significant intervention or assistance. V AT occurs when the product is considered to be fin- ished and in good working order (bug-free). This is an extremely important aspect of product development, as many entrepreneurs have "surefire" ideas not readily appreciated or desired by users (e.g., potato- flavored ice; yes, someone actually tried it). This can also be referred to as delta testing or enduser testing. See beta testing, gamma testing. user account An account assigned for a specific individual on a computer network or on a multiuser machine. A user account is a security system config- ured by the system administrator. The sophistication of the security can range from a simple name prompt at the time of login, to name and password logins at various levels of access, and different protections attached to directories, processes, and programs. User Agent VA. A network service used by clients to find available services on behalf of the user. See Directory Agent, Service Agent, Service Location Protocol. User Datagram Protocol UDP. An IETF-recommended protocol for the Internet which provides a datagram mode for Internet Protocol-based (IP- based) packet-switched network communications. UDP is primarily used with the Internet Name Server and Trivial File Transfer. The format ofUDP header is shown in the User Datagram Protocol Header chart. For more details about UDP, see See RFC 768. user event In programming, a type of input event which is signaled through an input device such as a mouse, joystick, keyboard, or touchscreen, and inter- preted into a response by the operating system or applications program. User events typically include button, window, or menu selectionsl adjustments and movement of icons, windows, or objects. The most challenging types of user events tend to occur in fast action video games and realtime graphics input pro- cessing. User Glossary Working Group UGWG. A group within the User Services Area of the Internet Engi- neering Task Force (IETF) which has created an In- ternet Users' Glossary. See RFC 1392. user group, user's group, users' group An organization of users of a particular product or service. A support group. With the introduction of computers, society took a technological leap that was difficult for anyone individual to understand or bridge. In order to facilitate the use and understanding of complex systems, programming languages, and technologies, many users' groups sprang to life, beginning in the mid-1950s, to provide mutual support and assistance in sharing information and meeting technological challenges. User Datagram Protocol (UDP) Header Format o 1 2 3 01234 5 6 7 890 1 2 3 4 5 6 789 012 345 6 7 8 901 + + + + + I Source I Destination I Port I Port + + + + + I Length I Checksum II + + + + + I Data octets '" + / Source Port Destination Port Length Optional. Indicates sending port. The default port for replies, zero if not used. Related to specified Internet destination address. User datagram length in octets, including the header and data. The minimum is eight. 967 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary The proliferation of users' groups is important not only for the support they provided to members, but also because this venue provided a forum for computer hobbyists, amateur radio groups, and many other amateur and professional enthusiasts to brain- storm ideas and contribute to the developing fields. The development of computer technology was no longer in the hands of large educational institutions and corporations. Individuals and small companies, particularly in the 1970s, had a window of opportu- nity during which they were able to make highly significant contributions to the development of the industry. userinterfaceill. The communications link through which a person interacts with a machine. On computers, the ill, in its broadest sense, includes the various symbolic text, images, sound, and other sensory cues and gadgets presented to the user, with which the user interacts. This is commonly done through peripheral devices such as touchscreens, keyboards, mice, joysticks, microphones, data gloves, and others not yet invented. It is considered the highest layer of the computer system structure, with the machine instructions for physical operations comprising the lowest layer. The user interface is the single most important aspect of computing and should never be undervalued. Com- puters were designed to serve the needs of people; if people are forced to adopt unhealthy or uncomfort- able habits to interact with computers, or if computers take time away from people rather than freeing them from repetitive tasks or drudgery, then human needs are not adequately served by the technology. User interfaces and software applications should be designed with the goal that the purpose of the technology is to improve the quality oflife. The design of user interfaces is an art. It demands common sense, a knowledge of ergonomics, psychol- ogy, philosophy, electronics, aesthetics, and a large dose of sympathy for a broad range of users. As such, user interfaces have developed in fits and starts, with many software programs providing very poor support for users, forcing the user to conform to the idiosyn- crasies of the machine (or the programmer who wrote the software), rather than the other way around. See user interface history. user interface history The earliest telecommunications interfaces consisted of physical semaphores (smoke, flags, and arms) and telegraph keys sending coded messages that needed to be decoded and tran- scribed when received. The received message was usually presented as a long paper tape inscribed with wiggly lines, dots and dashes, or punched holes. Computers up until the 1950s used a similar model. This kind of user interface wasn't very friendly, so inventors, even in the earliest days of telecommunications technology, sought ways to encode the alpha- bet, so that letters could be directly sent and received (eventually resulting in teletypewriters) without the operators doing the translation. But the basic meth- ods prevailed for decades, mainly because they could be used anywhere, with the simplest of equipment. 968 Telegraph key codes are still a requirement ofattain- ing amateur radio licenses. With the development of personal computers, user interfaces took a leap. The Altair microcomputer, sold originally as a hobby kit in 1984, had no monitor, mouse, or keyboard. It was programmed by means of flipping little dip switches; if you made a mistake, you had to start again. Yet within 2 years modem microcomputers, inspired partly by high-end systems with better resources than the Altair, came into being in the form of the TRS-80 and Apple computer, and keyboards and monitors became standard. Al- most every change since then has been an evolutionary refinement or logical addition rather than a revo- lutionary change. Even the lifelike and startling three- dimensional virtual reality world represents, for the most part, an evolutionary development, albeit an exciting one. Early computer user interfaces consisted primarily of monochrome screens displaying limited text, often with no lowercase letters, and large rectangular graphic blocks. While ingenious computing pioneers wrung astonishing surprises from this primitive technology, it was obvious that improvements were needed in order for a computer to be more fun, ver- satile, and consumer-friendly. User-to-User Indicator UUI. In ATM network Ad- aptation Layer 2 (AAL2), a 5-bit indicator in a 3-oc- tet-header CPS packet that follows the length indicator (LI) and precedes the header error control (HEC). Initially the PPT and UUI were separate fields, but were merged in the mid-1990s into one field, sometimes called the CPS-UUI field. The UUI field enables upper layers (users) to somewhat trans- parently convey parameters, for example. UserID User Identification. Aunique computer account designation used to gain access to a secure or monitored system. A UserID is frequently paired with a password for system access. Historically many systems accepted only eight characters for the UserID and, for backward compatibility, this limitation per- sists on many systems today. On networks using the most common mail systems, the UserID typically forms the first part of an email address. USGS See United States Geological Survey. USITA Formerly United States Independent Tele- phone Association. See United States Telephone As- sociation. USKA Union Schweizerischer Kurzwellen- Amateure Union (Union of Swiss Shortwave Ama- teurs). A member organization associated with the In- ternational Amateur Radio Union. http://www.uska.ch/ USOC See Universal Service Order Code. USOP User Service Order Profile. USPIX The USOC code for telephony-related maintenance plan, standard, levell, per line/circuit, UN!. USTA See United States Telephone Association. UTI A time reference based upon Earth's axis rota- tion. It is related to Coordinated Universal Time in that UTC was set to synchronize with UTI at 0000 hours on January 1, 1958. © 2003 by CRC Press LLC UTAM Since some of the frequencies used by incum- bent carriers have now been designated for USDC services (1890 to 1930 MHz), companies are chang- ing their operating equipment and software to oper- ate instead in the 2.0 GHz microwave C-band UTAM Inc. is an open industry resource for assisting in frequency relocation. See band allocations. UTC See Coordinated Universal Time. UTDR Universal Trunk Data Record. Utility Communications Architecture UCA. A comprehensive suite of communications protocols based upon open systems for use by electric utilities providers/maintainers. UCA began at the Electric Power Research Institute (EPRI), in 1988. UCA is a flexible, scalable architecture that can control various types of devices ranging from small local devices to those in major installations and control centers. UCA Version 2 has been developed to support the communication needs of Energy Management Sys- tems, Supervisory Control and Data Acquisition Sys- tems, Intelligent Electronic Devices, Remote Tenni- nal Units, and others. The standardization effort is intended to help utilities providers to intercommuni- cate through a variety of physical media, to reduce installation, operations, and migration costs, and to achieve secure communications through standard mechanisms. UCA documents are being assessed by an IEEE Stan- dards Coordinating Committee for review as potential IEEE standards. Utility Communications Architecture Forum UCA Forum. A group dedicated to promoting UCA and assisting individuals and companies in understanding, utilizing, and furthering this technology. http://www. ucaforum.org/ utility pole A sturdy tall pole installed in the ground (or on the ground in mountainous areas, supported by rocks and guy wires). The pole is used to support utility wires for power and telecommunications and may have crossbars and insulators. Utility poles are raised with the aid of long poles with spikes on the end called pike poles, or with industrial machines designed for the job. Most poles are made from logs, although some areas have metal poles; at one time in history, it was thought that metal poles would soon replace all the wooden poles, a prediction that didn't hold true. In some areas, especially avalanche areas, it was necessary to reinstall poles once or twice a year, a costly, time-consuming business, so various alter- natives were tried, including laying the wire along the ground. Unfortunately, rodents like to chew through the wires, causing almost as much interrup- tion to service as the avalanches. Transmissions in inclement regions are now often sent with microwave transceiving systems rather than with wires, a solution which requires less maintenance. See joint pole for more details and diagrams. See Universal Transverse Mercator Projection. UTM uuep Map A logical map describing the in- terconnections between intercommunicating UUCP- capable systems. A UUCP Map Entry is issued when a host is registered on the UUCP system. The main routing infonnation in UUCP-base networks is related to the UUCP Map and is contained in a pathalias database. Thus, for a message from mysite.org to be delivered to yoursite the path might be expressed as mysite.org sitel!site2!midsite3!yoursite!%s Because exclamation marks are traditionally used to separate the nodes, this is commonly called a "bang path" and veterans of the early email days can remem- ber typing bang paths into their email TO.' headers. In the early 1980s, the UUCP Map was still small enough to be represented on a single page, with systems such as ucbvax, menlo 70, decvax, and chico rep- resenting familiar interlinks to those who were using the system at the time. From this point, UUCP grew and spread to the point where static connections/ routing maps were no longer practical in the way they were in the early UUCP days. By the 1990s, map updates generally came from domain registrations rather than from manually submitted registrations. By 2001, it was announced that UUCP Maps would likely be replaced with XML for future registrations. There are sites on the Web that enable the UUCP Map to be queried for a specific entry. For example, a search for ucbvax lists the Internet mail routing entry as cs.purdue.edu!ucbvax!roS and the UUNET mail routing entry as decwrl.dec.com!decvax!purdue!ucbvax!%s The UUCP Map can also provide infonnation about site administrators. In Europe, UUCP Map entries are available through the backbone "netdir" selVice. Joint Utility Pole With a Variety of Cables A typical utility pole with crossarms bearing primary power lines, ceramic insulators, below which are transformers in cylindrical containers feeding power to secondary power lines, and local power drops to nearby residences and businesses. Below these are the telecommunications cables carrying voice and data services. 969 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary UTP See unshielded twisted-pair. UTR Universal Tone Receiver. UTS Universal Telephone Service. uuep UNIX-to-UNIX Copy. UUCP was a basic networking system developed in the mid-1970s by AT &T Bell Laboratories; it was distributed with UNIX in 1977. UUCP was quickly adopted by many educational and research institutions for disseminat- ing mail. Two years later USENET, the global public news forum, was established using UUCP. As UUCP spread and became an important medium for computer connectivity, it was ported to many other computer architectures. In 1997, UUCP mail routing was taken over by the UUCP Project. By the mid- 1980s national networks in other countries were being set up with UUCP, establishing it as an important catalyst for intercommunications and the development of distributed networks. Due to its increasing importance, formats for the transmission of electronic mail through UUCP were then standardized for mixed computer environments along lines developed by ARPA. In 1987, UUNET was founded to provide commercial UUCP and USENET access. See BITNET, Unix, UNIX, USENET, UUCP Project, UUNET, RFC 822, RFC 920, RFC 976. uuep Project A project initiated in the early 1980s to enable the exchange of electronic mail among com- municating sites using the UUCP store-and- fOlWard transport system. The UUCP Mapping Project en- deavored to create a single worldwide database of systems interconnected through UUCP, in addition to the determination of optimum data paths between systems. In 1997, the UUCP mail routing for UUNET site, created by Eric Ziegast, was turned over to the 970 UUCP Project currently coordinated by Stan Barber. SeeUUCP. http://www.uucp.org/ urn 1. See Unified User Interface. 2. See unique user identifier. 3. See User-to-User Indicator. UUIn See Universal Unique Identifier. UUNET A Unix-based network provider and backbone (long-haul network). UUNET provides Internet name serving, connectivity, MX forwarding, and news feeds. The formation ofUUNET was probably due in part to the Acceptable Use Policy (AUP) fo- cus on research and education enforced by the Na- tional Science Foundation's NSFNET. This stimu- lated commercial establishment of computer networks. In the 1980s, UUCP over long-distance dialup lines was the primary means by which providers, institutions, and individuals received their messages. However, Internet connectivity has become ubiquitous and the situation has changed. In the 1990s, UUNET is the only remaining significant network that uses UUCP transport for USENET messages. UUNET Canada, Inc. is located in Toronto; UUNET Technologies Inc. is located in Virginia. URN See Uniform Resource Name. UV See ultraviolet. UWB ultra wideband. uwe See Universal Wireless Communications. uwee See Universal Wireless Communications Consortium. UXTxx The USOC code for telephony-related sur- charges for emergency reporting services. The xx designates the region. For example, UXTMN refers to UXT services for Minnesota. © 2003 by CRC Press LLC v 1. symb. volt (may also be capitalized). See volt. V 1. symb. vacuum tube. See Audion, electron tube, vacuum tube. 2. symb. voltmeter. V & H Coordinates, V H Coordinates Vertical & Horizontal grid coordinates. Imaginary coordinate points on a virtual grid used to determine straight- line mileage between two specified points, with each exchange's location represented by a pair ofV & H coordinates. This is used for various products and services charged on a distance or mileage basis, as are long distance calls. The V&H system is based upon a 'flattened Earth' system from a Donald Elliptical Projection, developed by Jay Donald of AT&T in the mid-1950s. The basic idea is to create a triangular distance calcula- tion over a flattened surface. V & H Tape Vertical and Horizontal Coordinates Tape. A recorded tape provided primarily to assist with billing, it includes NXX types, major and mi- nor V& H coordinates (latitude- and longitude-like regional designations), LATA Codes, and other information related to long distance accounting and service areas. It can be purchased from Bellcore. Vdrive In analog video, a periodic signal related to the vertical component ofa frame that is constructed with sequential, repeating line scans. In standard systems, the V drive sends a pulse so that the electron gun returns from the bottom right comer of the video frame to the top left comer (during the vertical blank- ing interval) in order in position for imaging the next frame (or half-frame in an interlaced system). The horizontal and vertical sync are related so that pulses can be combined on a single wire, together comprising a composite video signal. A composite signal can be represented as Csync-red-green-blue and transmitted over four wires. Many computer monitors use a five-wire RGBHV system in which the H and V represent horizontal and vertical sync pulse components. See H drive, nega- tive-going video. V interface In ISDN, a number of reference points have been specified as R, S, T, U, and V interfaces. To establish ISDN services, the telephone company typically has to install a number of devices to create the all-digital circuit connection necessary to send and receive digital voice and data transmissions. The V interface is the reference point between the telephone switching office's exchange terminal switch and the line terminal switch. Thus, one side connects to the public telephone exchange and the other connects through the U interface to the subscriber's network termination (NTx) device. See ISDN interfaces for a diagram. Vnumber (symb. - v) In fiber optic lightguides, the normalizedfrequency parameter for describing the number of modes in a given fiber optic waveguide. The transmission of different guided or radiant modes in a fiber is based upon the materials used and their respective refractive indexes, the core diameter, and the relationship of the core to the reflective cladding that surrounds it. Mathematically, the V number can be expressed as 21t (which is the number of radians in a full circle) times the radius of the fiber core (in microns) which yields the circumference of the core. This is divided by the wavelength (in microns) times the numerical aperture of the fiber (square root n 2 J - n 2 i) where the numerical aperture (NA) is derived ttom tne core (nJ) and cladding (n2) relationship. Symbolically, the V number may be expressed as V= (21ta/l)NA. Smaller V numbers tend to be associated with single- mode fiber transmissions, while larger V numbers are associated with multimode fibers that can transmit more than one wavelength. Within multimode fibers, a larger V number is associated with a larger numerical aperture up to practical tolerances. The V number provides information that is useful in determining relationships between core and cladding relative to (1) the wavelengths that are intended for use with aparticular cable and (2) the beam width of the illumination source for the lightguide. See cladding, dominant mode, index of refraction, numerical aperture. VSeries Recommendations A set ofITU-T recommended guidelines for interconnecting networks and network devices. These are widely implemented in computer modems. The V Series specifications are available for purchase from the ITU-T, and a few may be downloadable from the Net. Some of the related general categories and specific V category recommendations ofparticular interest are listed here. See also I, Q, and X Series Recommendations. 971 © 2003 by CRC Press LLC . services. 969 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary UTP See unshielded twisted-pair. UTR Universal Tone Receiver. UTS Universal Telephone Service. uuep UNIX-to-UNIX Copy. UUCP was a basic networking system developed in the mid-1970s by AT &T Bell Laboratories; it was distributed with UNIX in 1977. UUCP was quickly adopted by many educational and research institutions for disseminat- ing mail. Two years later USENET, the global public news forum, was established using UUCP. As UUCP spread and became an important medium for computer connectivity, it was ported to many other computer architectures. In 1997, UUCP mail routing was taken over by the UUCP Project. By the mid- 1980 s national networks in other countries were being set up with UUCP, establishing it as an important catalyst for intercommunications and the development of distributed networks. Due to its increasing importance, formats for the transmission of electronic mail through UUCP were then standardized for mixed computer environments along lines developed by ARPA. In 1987 , UUNET was founded to provide commercial UUCP and. the ENIAC.It was designed and built in the mid-1940s by the Eckert-Mauchly Electronic Control Corpora- tion, but taken over before its completion by Reming- ton-Rand. UNIVAC was advertised as the UNIVAC File-Computer "electronic. rectangular graphic blocks. While ingenious computing pioneers wrung astonishing surprises from this primitive technology, it was obvious that improvements were needed in order for a computer to be more fun, ver- satile, and consumer-friendly. User-to-User Indicator UUI. In ATM network Ad- aptation