Fiber Optics Illustrated Dictionary transcontinental telegraph The first American transcontinental telegraph line was initiated by Hiram Sibley, with encouragement from Ezra Cornell, in the mid-1800s. Sibley, the founder of what was to be- come Western Union, made a reasonable estimate that it would take 2 years and about $1 million to com- plete the project. The telegraph line had a significant impact on the new Pony Express service, which had been in operation for less than 2 years when it shut down in October 1861, after inducements to stay in service at least until the telegraph line was completed. Not surprisingly, problems other than weather plagued the construction of the line. Buffalo discov- ered that telegraph poles made good scratching posts, sometimes bringing down the poles in their enthusi- asm. Native Americans sometimes made offwith the wires because the lines stretched through their treaty lands; within days or hours, exquisitely woven cop- per wire bracelets would appear in local trading mar- kets. Remarkably, despite the great distance, harsh conditions, and the small size of the work crew (only about 50 line workers), the transcontinental telegraph was completed in October 1861. It had taken only 4 months at a fraction of the projected cost, one of the most stunning achievements in western engineering. transducer A general term for a device which con- verts one form of energy to another, a process used throughout communications. When sound waves from a telephone conversation come in contact with a telephone mouthpiece diaphragm, the diaphragm causes small polished carbon granules to cohere and the energy is converted to electrical impulses that are transmitted along the phone line. When the mechani- cal movements ofa phonograph stylus are turned into electrical impulses, and then, at the speaker, con- verted again to audible sound waves, the signal has gone through ( at least) two transducers. transfer lens A lens that propagates light in a useful direction and may also concentrate or diffuse the light, as needed. The effecitve plane or working plane is that region over which the propagated light is op- timized for the needed purpose, which is often uni- formity and consistency of the light beam (usually perpendicular or nearly so to the plane of the light beam). In the context of light transfer from an illuminator to a fiber optic lightguide, a lens designed to propagate the light from a laser or light-emitting diode into an optical fiber core with a minimum of feedback to the laser. If the laser light hits the fiber lightguide in such a way that it reflects back, it can cause jitter or fluc- tuating performance in the laser. A hyperbolic lens surface, for example, can collimate laser light and further may transmit the light towards the fiber lightguide at angles that are efficiently re- lated to the axis of the fiber and the angle most likely to reduce reflections from the end of the fiber. Thus, there are compromises in which the most efficient balance of factors is sought. Toroidal, circular, or spherical lenses may be used as transfer lenses, depending upon the type of assem- 942 bly, power of the laser light, and diameter of the lightguide. The precision of the application (e.g., high-speed telecommunications) dictates, in part, how sophisticated or efficient the transfer lens may need to be, as will the degree of curvature of the fi- ber filament endface. A transfer lens may also couple photomultiplier tubes to CCD components in instruments such as spectrom- eters. Since traditional optical lenses for this purpose tend to be expensive and bulky, some instruments now use a fiber optic faceplate to provide a lighter, thinner coupling interface. Depending upon any size differences between the coupled parts, the fiber ar- ray may use fiber tapers rather than straight fiber fila- ments to guide all the light into a smaller or larger CCD components. See diffusion; face plate, fiber optic; Fresnel lens. transformer An electrical device for changing the qualities ofa current by mutual induction. Transform- ers did not come into wide use until the early 1900s, gradually superseding spark coils for providing power for communications and electronic components. They were similar to spark coils in that they had a core sur- rounded by conductive windings. However, the core used soft iron sheets rather than a bar. Like a spark coil, two sets of windings, one within the other, were commonly used. The core could be closed or open. Transformers required alternating current and direct current was still prevalent at that time, but the use of alternating current allowed the elimination ofa vi- brator, as the natural alternations of the current caused inductive discharge. This was more compact and practical than a spark coil. Since many modem electronic appliances (modems, printers, answering machines, model trains) have electrical requirements different from that which comes out ofa household socket (1 10 or 220 AC), the power cord may be equipped with a transformer which modifies the current to the needs of the device being powered (9 or 12 V is common). It is impor- tant to use the correct transformer; if the voltage is too high, it will likely blow the components. Transient Mobile Unit A mobile communications term for aunit that communicates through a foreign base station. transistor A small device developed in the late 1940s which provided a means to amplify signals with very low power consumption and very little heat. The name, derived from "trans-resistor," has been attrib- uted to John R. Pierce who worked with Schockley at Bell Labs. The importance of the transistor to the development and evolution ofelectronics cannot be overstated. A new world of tiny components opened up, including portable radios, hearing aids, comput- ers, satellites, and much more. See transistor history. transistor history The invention of the transistor in 1947 is widely attributed to William Shockley, John Bardeen, and Walter H. Brattain of Bell Laboratories, although Ralph Brown is sometimes also mentioned. Starting in 195 I, when they began to be commercially produced, transistors replaced large, power-hungry, cumbersome vacuum tubes, enabling electronics to © 2003 by CRC Press LLC transistor-transistor logic TTL. One of three main logic families, TTL logic circuit design is similar to diode transistor logic (DTL), but with multiple emit- ter transistors. TTL is based upon bipolar compo- nents, thus, when coupled, one can be used as the in- put component and one as the output component without any intervening resistors or other connect- ing components. This makes it faster than earlier tech- nologies, though not as fast as a similar circuit de- signed with emitter-coupled logic (ECL). TTL is sometimes called multi-emitter transistor logic. See emitter-coupled logic. transit In network communications, if a provider wants to send data to adestination but does not have the needed routing information, the provider may ar- range temporary, permanent, fee or no-fee access (transit) to the destination through a second provider that has the necessary information or access. See peering. transliterate To spell or represent the characters of one alphabet in the closest possible corresponding characters of another alphabet. Transliteration does not imply translation of the actual meaning of words composed of those characters. Western European lan- guages transliterate reasonably well. It is harder to transliterate between Cyrillic and Roman characters, and is decidedly a challenge to transliterate between pictographic or symbolic alphabets, such as Asian languages and sequential, phonetic alphabets such as western European languages. The difficulties in trans- literation on computing systems have led to many al- ternate keyboards, character mappings, and input sys- tems. See Unicode. transmission The sending of information through electrical signals. It is very common for information to be added to a signal through various forms of sig- nal modulation, often with a carrier wave. See car- rier wave, modulation. Transmission Control Protocol TCP. A widely used Internet and local area network (LAN) connection- oriented, packet-switching transmission protocol de- scended from previous DARPA editions. Together with Internet Protocol, the TCIPIIP combination is a means for the transport of host-to-host information over layer-oriented network architectures. See Inter- net Protocol, RFC 793. transmission header TH. In packet networking, a header that includes control information, and may be followed by a basic information unit (BID) or seg- ment. Used for network routing and flow. transmission level point TLP. In installation, test- ing, and maintenance, apoint in a conducting line at which the transmission level is measured according to whatever types of signals are sent through the con- ductor. In telephony, for example, the power level of a voice communication through an alternating cur- rent (AC) conductor may be measured in terms of decibels relative to a reference point. transmission medium Any material through which transmission is facilitated either due to its inherent characteristics or through inherent characteristics enhanced by technology. Common transmission The landmark patent for the transistor, an inven- tion that dramatically changed electronics. [U.S. patent document, public domain.} m.M ntJ./I Historic Transistor Patent be smaller and less expensive, and to run cooler and faster. (There are still some high-frequency applica- tions where the use of vacuum tubes is practical.) The development of the transistor was foreshadowed by the 1926 patent application of Julius Edgar Lilenfeld, who had devised a way to control the flow of current in a solid conducting body by establishing a third potential between the two tenninals. Later, in the 1970s, many types oftransistors were succeeded by semiconductors. See de Forest, Lee; Kilby, Jack St. Clair; Pickard, Greenleaf. transistor radio A radio developed in the 1950s, based on small semiconductor transistors instead of larger electron tubes. The smaller size and power con- sumption of transistors made it possible to design handheld portable radios, which became popular and widespread in the early 1960s. Portable radios were not new, since the early crystal detector sets required no outside power and could be carried around in a small case. However, practical, amplified, battery- driven portable radios did not become widespread until the development of small, low-cost transistor components. -J [- 943 © 2003 by CRC Press LLC Fiber Optics illustrated Dictionary media include air, light, wire, coaxial cable, fiber op- tics, etc. Broadcast transmissions primarily are sent through air, fiber, and coaxial cable. Computer trans- missions are typically sent through copper wire or coaxial cable, although the use of fiber is increasing. Various media vary greatly in the amount of infor- mation (bandwidth) they can carry at anyone time. See individual media for more detailed information. transmitter 1. That which transmits or sends through some means such as chemical, optical, or electrical signals. 2. A device that sends out a signal, such as a transmitting antenna, telegraph instrument, or mo- dem. Atransmitter may also include various mecha- nisms to amplify, compress, modulate, or encode a signal. See telephone transmitter. transparentA transparent technology is one in which the inner workings are not apparent to the user. For example, in computer operating systems with graphi- cal user interfaces, the user sees the applications through point-and-click icons, text windows, and resizable gadgets and dialogs. The conversion of the information into operating instructions, the device drivers, queuing mechanisms, buffers, priority and security mechanisms, and binary arithmetic are es- sentially in the background, and thus invisible or transparent during typical interactions. Transparent Bit-Oriented Protocol A protocol based on Bit Oriented Protocol (BOP) implemented on a number of Motorola communications products. TBOP is an access port type that accepts BOP frames and turns them into X.25 packets for transmission across a Frame Relay or X.25 network. It then depacketizes them for delivery to an end user device. Thus, BOP is used to transparently pass network in- formation among devices with different protocols. TBOP will pass aborted and damaged frames as well. See Bit Oriented Protocol. transparent tone in band TIIB. See tone in band. transponder, radio In radio communications, a transceiver that transmits information automatically, on receipt of an appropriate interrogation signal. transponder, satellite In satellite broadcasting, a device which receives and retransmits electromag- netic signals. Broadcast satellites employ this tech- nology with multiple transponders. With compres- sion, the capacity ofa transponder can be significantly increased. Transport A, Transport B See broadcast data trigger. Transport Protocol Data Unit TPDU. In the Open Systems Interconnect (OSI) layered network model, the transport layer organizes data into a TPDU, that is, a packet that has had transport layer data added. Similarly, the session layer organizes data into Ses- sion Protocol Data Units (SPDUs). The TPDU con- tains the Transport Service Access Point (TSAP) ad- dress and the user's data (payload). See Protocol Data Unit. Transport Layer Security Protocol TLS Protocol. Aclient/server-supporting protocol for securing net- work communications over the Internet. TLS is in- tended to deter eavesdropping, tampering, or forging 944 of messages. It was submitted as a Standards Track RFC by Dierks and Allen in January 1999. The TLS Protocol is primarily intended to provide privacy and data integrity between two communicat- ing applications. It is composed of the TLS Record and TLS Handshake protocols. The TLS Record Pro- tocol is layered over areliable transport protocol and provides connection security in terms ofprivacy and reliability through encapsulation ofhigher level pro- tocols. The TLS Handshake Protocol enables authen- tication of the client/server relationship and the ne- gotiation of an encryption algorithm and crypto- graphic keys prior to data transmission. See RFC 2246. Transport Service Data Unit TSDU In the Open Systems Interconnect (OSI) model, an item of in for- mation passed by the network transport user to the transport provider. In the Transport Protocol Data Unit structure, all the data of the TSDU comprise the User Data. In the ISO-SP protocol, up to four session protocol data units together may comprise the TSDU transportable cellular phone A transportable phone consisting ofahandset, antenna, and battery, usually bundled together in a carrying bag (sometimes known as "bag phones"). It's a little heavier than aself-con- tained, handheld cellular phone. This type ofphone can operate on up to 3 W of power. It can be oper- ated independently of a car battery and is typically used for field work that requires a phone with greater mobility and, sometimes, a larger antenna and longer life battery. It may include fax and modem features, and may be used in conjunction with a laptop. Jour- nalists, scientists, and business people who need something a little more full-featured than a simple handset system use transportable systems. trap v. To confine, narrow in on, circumscribe, or sur- round, especially with the implication that the object, person, or function cannot subsequently escape. trap door A hidden device or software mechanism that causes a naive user to "fall" into an application, environment, or system, while assuming it is a legiti- mate user account. The user then tries to access nor- mal applications, for example, leaving a trail of ac- tivities that can be logged, so that the trap door pro- grammer can later search the log for usemames, pass- words, or other information that can be used to pen- etrate an account. Since the user may begin to notice that the environment is not quite the same as normal, a trap door program may "inadvertently" crash or log out the user (or, on a network, say the system is go- ing down and advise the user to log out) in order to escape detection. The next time the user logs on to the genuine account, everything is normal. See back door, Trojan horse, virus. trapping In printing, a technique for assuring that adjacent inks meet, or slightly overlap so there won't be an undesirable, paper-colored gap between the inks if the registration of the press is slightly off. When a user creates desktop publishing page layouts intended for printing at high resolutions, settings must usually be adjusted to maximize trapping to ensure the qual- ity of the final product. Typically, small, light-colored © 2003 by CRC Press LLC objects like fonts are trapped (slightly overlapped) over dark ones, so that the detail in the small objects is not lost. See choking. traveling user TU. In a Secure Data Network Sys- tem (SONS), a traveling user is one who is visiting a Message Security Protocol-equipped (MSP- equipped) facility other than the usual one where the user reads and sends messages. In networks in gen- eral, a TU is someone who may interconnect or in- teract with a network from a variety of facilities while traveling. This type of network access is increasing as mobile systems become more prevalent. traveling-wave tube TWT. A tube in which a stream of electrons interacts in a more-or-Iess synchronized manner with a directed electromagnetic wave so en- ergy transfers from the stream to the wave. The ba- sic components ofa TWT include an electron gun for producing a high-density electron beam, a microwave circuit supporting a traveling electromagnetic wave through which the beam travels, and a collector to collect what is left of the electron beam that passed through the microwave slow-wave circuit. Amplifi- cation is attained through proximity of the electron beam to the traveling electromagnetic wave housed within a structure designed to propagate the wave. TWTs evolved from magnetron microwave-generat- ing tubes, emerging during the latter part of World War II. The TWT was designed by inventor Rudolf Kompfuer, and later improved by Kompfuer and John R. Pierce at Bell Telephone Laboratories. The Hughes Aircraft Company subsequently became a significant developer ofmilitary and commercial TWTs. The TWT was originally developed to support emerging radar technologies and is now also an important com- ponent in communications satellites and missile-seek- ing circuits. See cavity magnetron; Kompfuer, Ru- dolf; magnetron; phototube. TRE See Telecommunications Research Establish- ment. tree structureA common structure in computer pro- gramming and file organization. A tree branches from a main trunk to its various branches, just as the roots successively branch into subdivisions as you move away from the main trunk. Data branching structures are found in various database data storage schemes, file directory structures, fractal images, and more. Physical branching structures are found in network topologies; for example, branches may come off a backbone and branch further in individual local area networks (LAN s). Physical branching also occurs in phone circuits, with a main switching station supply- ing local private branches, which further subdivide to service individual lines within the local branch. Programmers use various types of tree structures in- cluding binary trees, B trees, B* trees, etc. TREG See Telecommunications Regulatory Email Grapevine. trellis coding A source coding technique used in a variety of contexts, from high-speed modems to MPEG decoding, to produce a sequence of bits from an incoming stream that conforms to certain desired characteristics. TRL transistor-resistor logic. Also called resistor- transistor logic (RTL). Varying numbers and types of transistors and resistors combined in a circuit to com- prise and control the logical operations of which the circuit is capable. TRIBES Tri-Band Earth Station. A commercial sat- ellite tracking station from California Microwave, Inc. (CMI), operating on C-, X-, and Ku-Band fre- quencies, aimed at government applications. TRIBES-Lite is a downsized version. triboelectricity Electricity generated by friction, as in a bicycle wheel-mounted generator that becomes charged when the wheel is spun and rubs against the generator contact surface. Triboelectricity can also be generated by rubbing a balloon on a person's hair, enabling the balloon to magnetically be attached to walls or other surfaces until the electricity dissipates again. See mutual capacitance, static electricity. tributary Secondary, or subsidiary peripheral, sig- nal or process. Subsidiary peripherals receive their control data from servers or devices higher up in a hierarchical network. Subsidiaries may be aggregated to create a combination medium or signal. See tree structure. triodeAn electron tube with three primary elements: an electron-emitting cathode, an electron-attracting anode, and a grid superimposed so that it can be used to control the flow of electrons. The invention of the triode by Lee de Forest, who named his commercial triode the Audion, is one of the most significant de- velopments in the history of electronics. Prior to the addition of the third element, it was not possible to control the electron flow to any useful degree. See Audion. TRIP 1. See Telephony Routing Over IP. 2. See To- ken-Ring Interface Processor. Trivial File Transfer Protocol TFTP. A simplified, lock-step client/server version of File Transfer Pro- tocol (FTP) for reading and writing files over net- works. TFTP was originally developed to work with diskless workstations but has since been applied to other applications. TFTP is easily implemented over Internet Protocol (IP) and provides only the most ba- sic file transfer features. It is encapsulated in UDP (standard over port 69) rather than TCP. A multicast option suggests a way to use multicast packets to allow multiple clients to concurrently re- ceive the same file. See Enhanced Trivial FTP, Simple File Transfer Protocol, RFC 1350, RFC 2090. trn A versatile, full-screen news reading program developed by Wayne Davison as a superset of rn, written by Larry Wall. This incarnation adds threads through ahierarchical database. Trojan horseA computer program that appears to be one thing, like a gift or incentive, but actually hides something more malicious or invasive, such as a vi- rus or other program that can infect a host system and potentially change or damage it. The name comes from the Trojan War during which Troy was pen- etrated by the gift ofa great wooden horse. Once in- side the fortress, soldiers swarmed from the horse to do battle with the surprised recipients. 945 • ' ':.~ :.~ ~ )1:~ ';~-" © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary Thus, a Trojan horse program is aprogram disguised as something desirable or benign, a pirate program, computer game, popular utility, appealing Web site, etc., in order to attract users. If the Trojan horse is an executable masquerading as a game, for example, running it unleashes its ability to change or take over a system. Unlike the Battle of Troy, however, the vic- tim may not realize his or her system has been in- vaded. The computer version ofa Trojan horse can be much stealthier than its historical counterpart while surveilling or damaging a system. Trojan horse programs are actually a particular type of masquerade program, by virtue of the fact that they offer something free or otherwise appealing. One example ofa Trojan horse program is a front- end that looks like a normal interface, but is really a visually or functionally identical layer on top of or instead of the interface that leads to something de- sired or appealing. It is designed to capture informa- tion to be used later for penetration of the system. For example, a programmer might create software that looks like a popular Web site or a network login prompt and then circulate information to entice people to use it. The user sits down at the terminal, registers for the service or types in an existing name and password, and gets an error message (from the Trojan horse) that the password was entered incor- rectly, try again, or that displays something appeal- ing and masks the fact that the usemame/password has been captured. The user sees a normal login prompt without being aware of the deception, types the password again, and logs in successfully or sim- ply continues to browse the site if the password prompt was fake. The writer of the Trojan horse has grabbed a name and password, with a low chance of detection by the user, and may now be able to access the user's account by means that are difficult to de- tect as unauthorized access. An Internet masquerade program was distributed in bulk email messages in summer 200 I, when PayPal online banking services were becoming popular. The businesslike innocent-looking email message had an embedded link to a fake PayPal Web site called paypal instead ofpaypal. The difference is that it used a capital "i" instead of an "I" (el), something few people would notice. When users tried to log on to the fake PayPal account with their usernames and passwords, the information was captured so that their real PayPal bank accounts could be accessed by the people who designed the masquerade. Fortunately, the ruse was discovered and reported quickly, but this example illustrates the potential for harming a large base of computer-naive Internet users. See back door, trap door, virus. troposphere The lower layer ofEarth's atmosphere, which contains clouds and most of the air, varying from a height of about 10,000 m at the poles to about 18,000 m at the equator. In radio transmissions, some frequencies can be bounced off the troposphere, that is, bent back to earth through super-refraction. See ionosphere, tropospheric scatter, tropospheric scat- ter transmission, tropospheric wave. tropospheric scatter The dispersion and propagation of waves resulting from the varied and discontinu- ous physical properties of the troposphere. This can be predicted and controlled sufficiently to be useful in communications. See tropospheric scatter trans- mission. tropospheric scattertransmissionA method of elec- tromagnetic wave propagation, employing frequency modulation, that exploits the irregular propagation properties of the troposphere. Tropospheric scatter transmission is a way to propagate, for example, mi- crowave transmissions for thousands of miles, in seg- ments up to about 500 miles per hop. tropospheric wave The troposphere includes a di- versity ofmoisture, heat, and other properties which can result in electromagnetic waves that undergo abrupt changes sufficient to create tropospheric waves distinguishable from the original tropospheric scatter transmission waves. trouble unit A systems diagnostic or descriptive measure to indicate the expected performance of a circuit over a given period of time. TRS See Telephone Relay Service. TRU See tone receiver unit. true bearing A bearing given with relation to geo- graphic north (north as it is shown on a globe), rather Trunk Carrier Implementations for Voice/Data Lines Desig. J-1 Mbps J-1 Channel T-1 Mbps T-1 Channel E-1 Mbps E-1 Channel -0 .064 1 64 Kbps 1 .064 1 -1 1.544 24 1.544 24 2.048 30 -IC 3.152 48 3.152 48 -2 6.312 96 3.152 48 8.448 120 -3 32.064 480 6.312 96 34.368 480 -3C 97.728 1440 44.736 672 -4 397.200 5760 274.176 4032 139.268 1920 -5 565.148 7680 946 © 2003 by CRC Press LLC than magnetic north (the north to which the north- seeking end ofa compass needle points). true north The Earth's geographic north. See mag- netic north. TrueType A system ofwidely used scalable vector- format !bnts developed by Microsoft Incorporated. See vector fonts. truncation 1. Cutting or chopping off at an end, sometimes abruptly. 2. The quick or abrupt termina- tion of an operation or process. 3. The removal of characters from the end ofa word or numeral, as in reducing a four-decimal numeral to two decimals without altering the numerals remaining (i.e., not rounding). Truncation applies to either the leading or trailing end, but more often than not, the part trun- cated tends to be the trailing end. trunk A communications link between two switches or distribution points. Ageneric term that applies to many technologies, but is most often used in connec- tion with telephone and network lines. Trunks can be set up to. be bidirectional (left to right to left) or uni- directional (right to left or left to right). See path, route. trunk carrierIn the past, this has referred to any tele- phone voice network trunk connection. It is now also more specifically associated with the digitally mul- tiplexed carrier systems used for digitized voice and data in North America, Europe, and Japan. The T-car- rier system ( for Trunk-carrier) in North America was the first of the X-carrier systems to be established, with Europe and Japan quickly adopting versions of it called the E-carrier and J-carrier systems, respec- tively. In general concept and fonnat, these systems are similar. In actual implementation, some impor- tant differences preclude direct compatibility. The Trunk Carrier Implementations chart illustrates the similarities and differences in terms of data rates and number ofvoice/data channels available in the three systems. See E-carrier, J-carrier, T-carrier. trunk exchange Hierarchically, a higher-level, spe- cialized telephone exchange facility dedicated to in- terconnecting trunk lines (which, in tum, connect tele- phone services users and carriers). The concept of a telephone trunk appears to date back to sometime around the 1890s. In the earliest manually operated switchboard systems, two operators were used to set up a trunk relay in which one would answer the calls coming from outside the exchange and the second would then connect the call to the appropriate local subscriber. In some of the historic telephone exchange diagrams, the fIrSt operator was designated "A" with the second designated "B" to illustrate the steps in- volved. Outgoing calls from the local exchange would go to Operator B and be passed on to Operator A to be connected to a line outside the local area. trunk group A group oftrunks sharing essentially the same electrical characteristics and often the same physical characteristics connecting to the same switching endpoints or connections. Multiple trunks are common in areas where one trunk would not be sufficient to carty the traffic. If the main trunk is busy, traffic may be manually or automatically switched to the next one in the group, and so on. See trunk hunting. trunk huntingAcall management system that seeks an available communications trunk over which to route a call. Economy is achieved by hunting the most frequently used trunks first. See hunting. trunk link frame TLF. In a crossbar telephone switching center there would be a frame supporting the links where subscriber telephone lines connected into the central office (CO) and a frame supporting the wires connecting to other switching offices. The lines connecting to other switching centers were ter- minated on the tronk link frames. The subscriber's line could thus be connected to another subscriber in the same local service area or to one of the trunk link circuits leading out of the service area on the trunk link frame connected to the appropriate remote of- fice. TS 1. See Technical Specification. 2. transmission scheme. TSACC See Telecommunications Standards Advi- sory Council of Canada. I TSAG See Telecommunication Standardization Ad- visory Group. TSAP See Transport Service Access Point. TSAPI See Telephony Services Application Pro- gramming Interface. TSAPI Service Provider TSP. A software driver that enables a TSAPI device to be adapted to a vendor's private branch exchange (PBX) system. The TSP may be used in conjunction with other computer telephony integration (CTn products, but is the minimum es- sential software that links the systems. See Telephony Services Application Programming Interface. TSB 1. Technical Service Bulletin. Bulletins issued by the Teleccommunications Industry Association. 2. See Telecommunication Standardization Bureau. TSDU See Transport Service Data Unit. TSO time share operation. TSP 1. See Telecommunications Service Priority. 2. See TSAPI Service Provider. TSR tag-switching router. See tag switching. TSRM Telecommunication Standards Reference Manual. TTA See Telecommunications Technology Associa- tion. TTAB transparent tone above band. See tone above band. TTC See Telecommunications Technology Commit- tee. TTIB transparent tone in band. See tone in band. TTL See transistor-transistor logic. TTS text-to-speech. A type of speech synthesizer. TTY service Teletype service. Depending upon the area, this is ateletype service made available to those with hearing impairments, at a price commensurate with that paid by regular telephone subscribers. The program is supported through the combined fees paid by all subscribers in a region. Eligibility for the ser- vice is usually determined by local health services agencies. TUANZ Telecommunications Users Association of New Zealand. 947 © 2003 by CRC Press LLC Tuning Coils Fiber Optics Illustrated Dictionary TUBA TCP and UDP with Bigger Address. One of three candidate protocol proposals eventually blended into IPv6 by the Internet Engineering Task Force (IETF). See IPv6. TUe I. total user cal1s. An accounting/administra- tive count of the total number of cal1s made per a specified period. 2. See Total User Cel1s. TUG Telecommunication User Group. Till See telephone user interface. tumbling A type of cel1 phone fraud that involves successively switching the electronic serial number for each call too quickly for the cel1 operator to de- tect the user. tungsten A heavy metallic element with properties similar to chromium and molybdenum used in elec- trical installations, filaments, and contact points, and for hardening alloys. tuning To adjust to resonate at a particular wave- length, as setting an instrument to a specific pitch or setting a radio antenna or tuner to receive aparticular frequency of radiant energy. See tuning coil. Historic radio tuning coils resemble large spools. Theyofien came in sets, designedfor difJerentfrequen- cies, and could plug into the circuit by means of two or more prongs. Since tuning coils could bepurchased in sets, they often included a base to keep the coils in order and protectedji"Om damage. These excellent examples are from the American Radio Museum collection. tuning coil A winding coil specifically configured to pick up certain frequencies of radiant energy, particu- larly radio waves. Early tuning coils consisted of nothing more complicated than a coil of fine conduc- tive wire wound around a wooden or rubber core, with the coil in circuit with aconnecting pin or pins. Tun- ing coils for consumer sets tended to range from the size ofa sewing spool to about the size of a human hand. Often they were stored like thread in banks or 948 rows on little wooden shelves, so that the appropri- ate frequency coil could quickly be selected and in- serted in a connector on the radio. The wire on each coil would be slightly different, to pull in a different frequency range, with different thicknesses and spac- ing between successive windings. Sometimes a smal1 sliding tab or knob attached to a bar would be placed along the edge of the winding, in order to make contact with a specific portion of the winding to provide further fine control. This was called a slide contact. Other tuning coils used a type of intricate basket weaving in various patterns supported by a slender frame in such a way that a lot of wire could be wound into a smal1 space and no cylindrical spool used. See basket winding, coil. tunnel n. 1. A hollow tube, conduit, or passageway through an obstruction. 2. In software, an intermedi- ary program that provides a temporary relay between connections without interpreting or otherwise chang- ing the content of the communication. A tunnel of- ten provides a temporary portal for passing data through a system such as a proxy, and ceases to exist when the ends of the connection are closed. tunneling 1. Encapsulating a network transmission in an IP packet for secure transmission over a net- work. See virtual private network. 2. To temporarily reroute a network transmission packet in order to uti- lize routers which would not normal1y be able to route the transmission to the original destination due to not having the needed destination entry. TUR Traffic Usage Recorder. Thring, Alan Mathison (1912-1954) A British math- ematician who traveled to Princeton in 1936, where he studied as agraduate student, and wrote On Com- putable Numbers He proposed some provocative ideas in ordinal logics and created a cipher machine while at Princeton, but Turing is best remembered for his description ofa hypothetical device which could handle logical operations and manipulate symbols on infinite paper tape. This Universal Turing Machine is described as ajinite state machine due to the finite set ofinstructions from which individual actions were derived. This provided the roots for thinking about computers in terms ofalgorithms and equations, and for positing devices that could be used for all pos- sible tasks. Many of the conceptual roots ofcomputer science, particularly general purpose machines and reusable code, were developed through his research. See Turing machine. Turing machine A hypothetical model devised by Alan M. Turing, which could handle logical opera- tions and manipulate symbols on infinite paper tape. This Turing machine is described as ajinite state machine due to the finite set of instructions from which individual actions were derived at that point. Many extrapolations from and implementations of these basic concepts have contributed to the devel- opment ofcomputing devices. See Turing test. Turing test In 1950, Alan Turing published "Com- puting Machinery and Intel1igence' in Mind, a philo- sophical journal. In it much of his thinking of the last © 2003 by CRC Press LLC few years was put into print, providing an effective inspiration to many future scientists and providing some of the concepts that developed into the field of artificial intelligence (AI). The Turing test was a pro- vocative assertion that computers would, in the suc- ceeding 50 years, be able to pass for a human under certain test conditions. Imaginative efforts to support this prediction have led to a wide variety ofinterest- ing programs, and prizes are offered for innovative software that can pass the Turing test. turnaround time The time of a transaction, espe- cially one that passes from one hand to others and back, as in sending something to another department or external service bureau. For example, the turn- around time for ordering a network connection may be two weeks by the time the order is tendered, the installer arrives and the system is up and running. 2. In network transmissions, the time it takes to send a transmission and receive an acknowledgment that the transmission was received, or can continue. 3. In detecting or pinging another system, the time it takes for the signal to reach the other system, and report back statistics on the connection. The phrase turn- around time is sometimes applied loosely to the time it takes for a human to send out a signal and receive an acknowledgment, and sometimes more precisely to the number of clock cycles or actual measured time it takes for the signal to leave the sending site, reach the receiving site, and report back to the sending site, used for system diagnostics and tuning. Or even more specifically, in handshaking or half-duplex applica- tions, turnaround time is the interval that occurs when the system switches to communication in the other direction. In terms of half-duplex satellite phone con- versations, this turnaround time is perceived as a blip, lag, or break in the line by the callers, and, if it is long, can distract from the conversation. See hysteresis. turnkey system Aself-contained system that can be purchased, installed, or relocated as a unit or as a package. Turnkey systems typically arise from two situations: 1. The technology is complex and the ven- dor combines options in such a way that the system meets a need but need not be configured or techni- cally understood by the user. The user simply pur- chases it, turns it on, and uses it. For example, many video outlets bundled Video Toaster systems as turn- key solutions for desktop video applications. 2. Many options are available for configuring a system, and the vendor best knows how to combine and config- ure the individual components to meet the needs of the purchaser. Private branch telephone systems and multiline telephone systems with lots of options are often bundled and purchased this way. turnstile antennaAn antenna comprising two dipole antennas perpendicular to one another with axes in- tersecting at their midpoints. turntable 1. Around, rotating platter, frequently with a central shaft or outer rim to hold objects in place, commonly used for playing audio and visual media, especially vinyl phonograph records. 2. A round, ro- tatable, platelike surface designed to give easy access to objects placed on it by turning. A Lazy Susan. Turn- tables are used in loading platforms, cupboards, mi- crowave ovens, and Chinese food restaurant tables. TVM See time-varying media. TVRO television receive-only TWAIN An image-oriented communications proto- col standard widely used in computer scanning de- vices and digital cameras (which are, in essence, por- table scanners). Most high-end graphics programs can handle TWAIN-compliant devices, as can many op- tical character recognition systems. TWAIN is sup- ported and promoted by a number of graphics indus- try vendors, including Eastman Kodak, Hewlett- Packard, UMAX, Adobe Systems, and others. See Tag Image File Format. tweak freak A technical user who is exaggeratedly interested in the inner workings, whys, and wherefores of the tiniest technical details in a system. This characteristic is an asset when diagnostics and fine-tuning are needed, and a liability in general so- cial situations. twinning Systems configured in parallel to create redundancy, or alternate means of access or transmis- sion. Twinning is sometimes done to install a new system while an old one is still used, or to provide a backup in the case of emergencies. In newer technolo- gies, twinning can provide backups or transition sys- tems until the old system is little used or phased out, such as twinning word processors with typewriters or physical facsimile machines with software fac- simile programs. twist length Also called lay length, this is the dis- tance from one twist to the next in a twisted-pair con- ducting cable. For example, a cable with a lay length of4 inches will correspond to three twists per foot or 3 TPF. In electrical-conducting wires, the twist length is kept as short as possible and helps to electromag- netically couple the cable while reducing crosstalk. In light-conducting fiber optic cables, the twist serves aphysical bundling purpose rather than an electrical coupling purpose. Helical twisting together of the tiny fiber optic filaments facilitates the installation of the cable and provides added strength. See twisted-pair cable, twists per foot. twisted-pair cable Twin strands or cores of inter- twined, insulated copper wire, a wire type used for many decades in the telephone industry. The twists are organized to help reduce interference in wires that are kept as close to inhabiting the same physical space as is possible. Thicker cables tend to provide cleaner transmissions, at a higher cost. Unshielded twisted pair (UTP) is commonly sold as four pairs of 24-gauge wire. Shielded twisted pair (STP) is commonly used in applications where there may be interference from other nearby electrical sources. Although the theoretic data transmission limit of twisted pair has been underestimated many times, and improved with new ideas and data protocol schemes, it is generally accepted that their practical capacity under normal operations is about 56 kbps. Twisted pair is now also commonly used in Ethernet LAN connections. Twisted-pair cable is sold commercially 949 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary VTP and CAT-5 Cable Assemblies Simplified images offour types of cables commonly used in telephony, video, and data cabling. in several grades of transmission performance. See category ofperformance. See twists per foot. twists per foot TPF. A measure of the number of twists (helical intertwinings) per foot length in apair of wires called twisted-pair wiring cable. The den- sity of the twists per length affects the bulk and flex- ibility of the cable and the degree ofelectromagnetic emanations associated with the wire when it is used as an electrical conductor. Increased twisting gener- ally increases the transmissions length. Uneven twists are generally used to reduce interference along the line from crosstalk and external sources. There are industry standards for the number oftwists per foot. For example, for Category 1 and Category 3 plenum and PVC for cables for regular applications, there are at least two TPF. Category 3 cables for tele- phony applications typically have 3 TPF with a gauge of 22 to 24 AWG. Cat 5 cable, suitable for the higher demands of fast data communications, may range from 8 to 36 TPF. The number of twists depends upon wire gauge, data transfer rates, and the number of twisted pairs included in a bundle. High-quality cables usually have evenly spaced twists that do not overlap. Different twist lengths in bundled cables can further aid in minimizing crosstalk. American Wire Gauge (AWG) # 18 cable has 5 TPF. See twist length. two-electrode vacuum tube, Fleming oscillation valve A historically important electron tube devel- oped by John A. Fleming. The two-electrode tube consisted ofa simple filament (cathode) and an elec- tron-attracting metal sleeve (anode) that fit around the top of the filament, both of which were housed in an evacuated tube. With no controlling mechanism, it wasn't of much practical use, but it was a history- making invention nonethless. Lee de Forest acquired a Fleming tube, experimented with it and created a three-element tube by adding a grid. This made it possible to control the flow of electrons from the cath- ode to the anode, an innovation that subsequently opened the door to the entire electronics industry. See Audion; de Forest, Lee; Fleming, John. two tone keying A means ofusing two tones, one for mark and one for space, to modulate a telegraph sig- nal so as to create two channels transmitting in the same direction. two-phase codingA means ofincreasing data trans- missions by splitting the signal into two orthogonal channels, one which is in phase and one which is a quadrature signal. They are then transmitted simul- taneously with this 90 degree phase offset, each op- erating at half the data rate of the originating signal. Thus, a signal might be transmitted at the same data rate in half the bandwidth, but for the trade-off of converting it from a baseband signal to a passband signal when splitting it into two channels. The increased potential for noise, when two signals are transmitted simultaneously is also a consideration. two-way trunkAnetwork trunk which operates in - oth directions. In the case oftelephone service trunk ines, it refers to one which can be seized from either nd of the connection, as opposed to one-way trunks, hich may be set up to send only or receive only. WPD traveling-wave photo detector. See photodet- ector, traveling-wave tube. ____ core individual fibers or fiber bundles secondary conductor / insulating layer . I copper wire ____ conducting core cladding I Top: A basic unshielded twisted-pair (UTP) cable; two-wire and four-wire UTP cables are especially common in telephone wiring (the copperpairs are en- twined within the sheath). Shielded twisted pair (STP) looks similar, but has an insulating shield under the water-resistant sheath. The outersheath is not neces- sary for all types of wiring, but is commonly used. Middle: Category 5 unshielded twisted-pair (UTP) cable suitable for the higher demands of data cables. Pairs are typically identified by color schemes that include a solid color and apaired stripedwire of the same color. For applications such as Ethernet, the wires are usually attachedto an RJ-45 connector that resembles a fat phone cable connector. LowerMiddle: Coaxialcable, so-calledbecause two conductors are housedwithin the covering, separated by an insulating layer to reduce crosstalk and to pre- vent short circuits that would occur if the two con- ducting layers touched. This is commonly used for video transmissions. Bottom: Fiber optic cable based upon light-guid- ingfilaments rather than electricity-conductingwire. This is commonly usedfor fast digital data communi- cations. The three top cables use copper for the central con- ducting core. - '=1" 1 1 copper wire conducting . color-coded pairs water-resistant insulation / sheath !~ 1 water-resistant sheath 950 © 2003 by CRC Press LLC TWS two-way simultaneous. A mode in which a router optimizes communications over a full-duplex serial line. TWT See traveling-wave tube. TWX Teletype- Writer Exchange. A Bell system print- ing telegraph service which could operate over the existing long distance network, established in the 1930s. In 1970, Western Union purchased the TWX service from AT&T and merged it into its own Telex service. See Western Union. Twyman-Green interferometer See interferometer. Tx, TX transmit. TxD transmit data. A data channel, typically used in serial communications, which is an output for DTE devices and input for DCE devices. See DTR, DSR, RTS, RxD, RS-232. Fleming Valve - Two-Electron Tube metal sleeve f ""'~ - (anode) filament (cathode) The Fleming valve was a landmark invention that led to the evolution of three-element vacuum tubes. The Fleming valve was limited in practicality, how- ever, in that it only included two elements, afilament (cathode) and a metalsleeve (anode) thatfit over the filament to attract electrons. There was no wayto con- trol electronj1ow. Itwas not untilLeede Forest added a controlling grid to create a three-element tube that the Audion was born to create the electronic age. TYMNET Ahistoric, commercial, X.25-based data network access service descended from the ARPA- NET. TYMNET became available in 1974, not long after Telenet was offered, at dialup-line speeds of 300 baud! The service was offering faster data rates (I200-baud) within a few years. By the mid-I980s 2400-baud service was offered, with 9600-baud fol- lowing in the late 1980s. This is pretty slow compared to current TI, ISDN, DSL, and cable modem stan- dards, but 9600 was pretty ripping in the 1980s. TYMNET grew and internationalized, with nodes as- signed regionally, which may not seem impressive to current Internet users, but in those days, regional nodes made it possible, in some countries, to dial TYMNET as a local call from anywhere in the region. It was a pretty exciting development at the time and a foreshadowing of global network access. A large number of companies eventually offered time- share or database information services over TYMNET, including Compuserve, Cybershare, the European Space Agency (ESA), Dow Jones, Dun and Bradstreet, Xerox Computer Services, and many more. TYMNET could be accessed in a number of ways, including through Datapac links. With the ad- vent of the Internet, TYMNET has been all but for- gotten, but it holds an important place in the growth of shared computing resources and access to comput- ers by the general public. Tyndall, John (1820-1893) A multitalented Irish physicist who rose far above his modest background, Tyndall studied the atmosphere, thermodynamics, electromagnetism, light guiding, and solar chemis- try. He passed on his loves of science and mountain- eering as an educator and popular lecturer. In 1870, he demonstrated to the British Royal Soci- ety that light could transmit through an arc.ing stream of water, a concept pioneered by 1-D. Colladon in 1841. This idea oftotal internal reflection, in which the optical rays cannot escape the medium within which they are traveling, is fundamental to fiber op- tic networks. Tyndall succeeded Faraday as director of the Royal Institution of London. Many scientific instruments are descended from his work, including fluorometers and UV and infrared spectrometers. See Colladon, Jean-Daniel. Type l/Type 2/Typex card A standardized, compact data card commonly used for modems, memory, and other plugin accessories for computers, digital cam- eras, and more. See PCMCIA card, PCMCIA standards. Type 1/Type3 font The designations for the most commonly used PostScript-format ASCII or binary outline (vector) font format first released by Adobe Systems in the mid-1980s. The character shapes for symbols in the fonts are defined in PostScript so that they can be printed from the vector description to the best resolution possible on a PostScript-compatible output device. In simple terms, this means they look good if they are printed small and they still look good when they are printed billboard size, because the shapes are mathematically derived rather than scaled up, as with bitmapped raster images. Type 1 and Type 3 fonts are not just character shapes, they are graphic expressions of programming algo- rithms, which means the characters can be swirled and manipulated and set across curved surfaces in a way that drawn fonts cannot. In theory, PostScript fonts could be animated. Type 3 fonts have some ad- ditional capabilities for special effects. PostScript Type 1 fonts are largely responsible for the desktop publishing revolution that occurred in the mid-1980s when Macintosh computers and Post- Script-capable LaserWriter printers were paired up with desktop publishing software. Before 1984, type- setting machines costs hundreds of thousands of dol- lars and the general public couldn't do much better than to use a special proportional typewriter. See Post- Script. 951 © 2003 by CRC Press LLC . Lines Desig. J-1 Mbps J-1 Channel T-1 Mbps T-1 Channel E-1 Mbps E-1 Channel -0 .064 1 64 Kbps 1 .064 1 -1 1.544 24 1.544 24 2.048 30 -IC 3.152 48 3.152 48 -2 6.312 96 3.152 48 8.448 120 -3 32.064 480 6.312 96 34.368 480 -3 C 97.728 1440 44.736 672 -4 397.200 5760 274.176 4032 139.268 1920 -5 565.148 7680 946 ©. bearing given with relation to geo- graphic north (north as it is shown on a globe), rather Trunk Carrier Implementations for Voice/Data Lines Desig. J-1 Mbps J-1 Channel T-1 Mbps T-1 Channel E-1 Mbps E-1 Channel -0 .064 1 64 Kbps 1 .064 1 -1 1.544 24 1.544 24 2.048 30 -IC 3.152 48 3.152 48 -2 6.312 96 3.152 48 8.448 120 -3 32.064 480 6.312 96 34.368 480 -3 C 97.728 1440 44.736 672 -4 397.200 5760 274.176 4032 139.268 1920 -5 565.148 7680 946 ©. possible to design handheld portable radios, which became popular and widespread in the early 1960 s. Portable radios were not new, since the early crystal detector sets required no outside power and could be carried around in a small case. However, practical, amplified, battery- driven portable radios did not become widespread until the development of small, low-cost transistor components. -J [- 943 © 2003 by CRC Press LLC Fiber Optics illustrated Dictionary media include air, light, wire, coaxial cable, fiber op- tics, etc. Broadcast