Fiber Optics Illustrated Dictionary - Part 96 potx

transit In network communications, if a provider wants to send data to a destination but does not have the needed routing information, the provider may ar-range temporary, permanent, fee

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 ofthe 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 Theeffecitveplane or workingplane

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 oflight 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 thatitreflects 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 ofthe 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-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 Anelectrical 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 ofwindings, 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 of a vi-brator, as the natural alternations ofthe 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 of a household socket (1 10 or 220 AC), the power cord may be equipped with a transformer which modifies the current to the needs ofthe 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 a unit that communicates through a foreign base station

transistor Asmall 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 BellLabs The importance of the transistor to the development and evolution of electronics 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 ofBell 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

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 outin-put 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 a destination 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 ofthe actual meaning ofwords composed ofthose 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 difficultiesin 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 Awidely 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, a point in a conducting line at which the transmission level is measured according

to whatever types ofsignals 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 ofthe 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

[-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 A transmitter may also include various

mecha-nisms to amplify, compress, modulate, or encode a

signal See telephone transmitter

transparent Atransparent 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

transparentduring 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

A client/server-supporting protocol for securing

net-work communications over the Internet TLS is

in-tended to deter eavesdropping, tampering, or forging

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 a reliable transport proPro-tocol 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 infor-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 Atransportable phone consisting of a handset, antenna, and battery, usually bundled together in a carrying bag (sometimes known

as "bag phones") It's a little heavier than a self-con-tained, handheld cellular phone This type of phone 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

trapv.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 theinks

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

objects like fonts are trapped (slightly overlapped)

over dark ones, so that the detail in the small objects

is not lost See choking

traveling userTU 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 offacilities while

traveling This type of network access is increasing

as mobile systems become more prevalent

traveling-wave tubeTWT Atube in which a stream

ofelectrons 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, emergmicrowave-generat-ing durmicrowave-generat-ing 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 of military 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

TRESee Telecommunications Research

Establish-ment

tree structureAcommon structure in computer

pro-gramming and file organization Atree 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 (LANs) 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

TREGSee Telecommunications Regulatory Email

Grapevine

trellis codingA source coding technique used in a

variety of contexts, from high-speed modems to

MPEG decoding, to produce a sequence ofbits 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

TRIBESTri-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

triboelectricityElectricity 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

tributarySecondary, 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

triodeAnelectron 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

TRIP1 See Telephony Routing Over IP 2 See To-ken-Ring Interface Processor

Trivial File Transfer ProtocolTFTP 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

trnA versatile, full-screen news reading program developed by Wayne Davison as a superset ofrn,

written by Larry Wall This incarnation adds threads through a hierarchical database

Trojan horseAcomputer 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 of a great wooden horse Once in-side the fortress, soldiers swarmed from the horse to

do battle with the surprised recipients

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Fiber Optics Illustrated Dictionary

Thus, a Trojan horse program is a program 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 ofTroy, however, the

vic-tim may not realize his or her system has been

in-vaded The computer version of a Trojan horse can

be much stealthier than its historical counterpart while

surveilling or damaging a system

Trojan horse programs are actually a particular type

ofmasquerade program, by virtue ofthe fact that they

offer something free or otherwise appealing

One example of a 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.Itis designed to capture

informa-tion to be used later for penetrainforma-tion ofthe 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,tryagain, 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 of Earth'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 scatter transmission Amethod ofelec-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 of moisture, 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

than magnetic north (the north to which the

north-seeking end of a compass needle points)

true northThe Earth's geographic north See

mag-netic north

TrueTypeA system of widely 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 operatermina-tion or process 3 The removal of

characters from the end of a 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

trunkAcommunications link between two switches

or distribution points A generic 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 carrierInthe past, this has referred to any

tele-phone voice network trunk connection.Itis 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-riersystem (for Trunk-carrier) in North America was

the first of theX-carrier systems to be established,

with Europe and Japan quickly adopting versions of

it called the E-carrier and J-carrier systems,

respec-tively.Ingeneral concept and fonnat, these systems

are similar.Inactual implementation, some

impor-tant differences preclude direct compatibility The

Trunk Carrier Implementations chart illustrates the

similarities and differences in terms ofdata rates and

number of voice/data channels available in the three

systems See E-carrier, J-carrier, T-carrier

trunk exchangeHierarchically, a higher-level,

spe-cialized telephone exchange facility dedicated to

in-terconnectingtrunklines (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.Insome ofthe 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 groupA group of trunks 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 Ifthe main trunk is busy,

traffic may be manually or automatically switched to

the next one in the group, and so on Seetrunkhunting trunk huntingA call 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 thetronk link frames. The subscriber's line could thus be connected to another subscriber in the same local service area or to one ofthe 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

TSACCSee Telecommunications Standards

TSAGSee Telecommunication Standardization Ad-visory Group

TSAPSee Transport Service Access Point

TSAPI See Telephony Services Application Pro-gramming Interface

TSAPI Service ProviderTSP 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 TSB1 Technical Service Bulletin Bulletins issued

by the Teleccommunications Industry Association

2 See Telecommunication Standardization Bureau TSDUSee Transport Service Data Unit

TSOtime share operation

TSP 1 See Telecommunications Service Priority

2 See TSAPI Service Provider

TSRtag-switching router See tag switching TSRMTelecommunication Standards Reference Manual

TTASee Telecommunications Technology Associa-tion

TTABtransparent tone above band See tone above band

TTCSee Telecommunications Technology Commit-tee

TTIBtransparent tone in band See tone in band TTLSee transistor-transistor logic

TTStext-to-speech A type of speech synthesizer TTY serviceTeletype service Depending upon the area, this is a teletype 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 serser-vices agencies

TUANZTelecommunications Users Association of New Zealand

Tuning Coils

Fiber Optics Illustrated Dictionary

TUBATCP 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

TUGTelecommunication User Group

TillSee telephone user interface

tumblingA 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

tungstenA heavy metallic element with properties

similar to chromium and molybdenum used in

elec-trical installations, filaments, and contact points, and

for hardening alloys

tuningTo adjustto resonate at a particular

wave-length, as setting an instrument to a specific pitch or

setting a radio antenna or tuner to receive a particular

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 be purchased 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 coilAwinding coil specifically configured to

pick up certain frequencies ofradiant 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 a connecting pin or pins

Tun-ing coils for consumer sets tended to range from the

size of a sewing spool to about the size of a human

hand Often they were stored like thread in banks or

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 windspac-ings

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 ofwire could be wound into a smal1 space and no cylindrical spool used See basket winding, coil

tunneln 1 A hollow tube, conduit, or passageway

through an obstruction 2 In software, an intermedi-ary program that provides a temporintermedi-ary relay between connections without interpreting or otherwise chang-ing the content of the communication A tunnel of-ten provides a temporaryportalfor passing data through a system such as a proxy, and ceases to exist when the ends of the connection are closed

tunneling1 Encapsulating a network transmission

in an IP packet for secure transmission over a net-work See virtual private netnet-work 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

TURTraffic Usage Recorder

Thring, Alan Mathison(1912-1954) ABritish math-ematician who traveled to Princeton in 1936, where

he studied as a graduate student, and wroteOn

ideas in ordinal logics and created a cipher machine while at Princeton, but Turing is best remembered for his description of a hypothetical device which could handle logical operations and manipulate symbols on infinite paper tape This Universal Turing Machine

is described asajinite statemachine due to the finite set ofinstructions from which individual actions were derived This provided the roots for thinking about computers in terms of algorithms 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 machineA hypothetical model devised by Alan M Turing, which could handle logical opera-tions and manipulate symbols on infinite paper tape

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 of computing devices See Turing test

Turing testIn1950, Alan Turing published "Com-puting Machinery and Intel1igence' inMind,a philo-sophical journal.Init much ofhis thinking of the last

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 of

interest-ing programs, and prizes are offered for innovative

software that can pass the Turing test

turnaround timeThe 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.Innetwork transmissions, the time it takes to send

a transmission and receive an acknowledgment that

the transmission was received, or can continue 3.In

detecting orpinging 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 ofclock 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.Interms ofhalf-duplex satellite phone

con-versations, this turnaround time is perceived as a blip,

lag, or break in the line by the callers, and, ifit is long,

can distract from the conversation See hysteresis

turnkey systemA self-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 antennaAnantenna comprising two dipole

antennas perpendicular to one another with axes

in-tersecting at their midpoints

turntable1 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 ALazy Susan

Turn-tables are used in loading platforms, cupboards, mi-crowave ovens, and Chinese food restaurant tables TVM See time-varying media

TVROtelevision receive-only TWAINAnimage-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 ofgraphics indus-try vendors, including Eastman Kodak, Hewlett-Packard, UMAX, Adobe Systems, and others See Tag Image File Format

tweak freakA technical user who is exaggeratedly interested in the inner workings, whys, and wherefores ofthe 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

twinningSystems configured in parallel to create redundancy, or alternate means ofaccess 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 ofemergencies.Innewer 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 lengthAlso calledlay 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 3TPF.Inelectrical-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

a physical bundling purpose rather than an electrical coupling purpose Helical twisting together ofthe tiny fiber optic filaments facilitates the installation of the cable and provides added strength See twisted-pair cable, twists per foot

twisted-pair cableTwin 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

Fiber Optics Illustrated Dictionary

VTPand CAT-5 Cable Assemblies

Simplified images offour types ofcables commonly

used in telephony, video, and data cabling.

in several grades of transmission performance See

category of performance See twists per foot

twists per footTPF A measure of the number of twists (helical intertwinings) perfootlength in a pair

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 of electromagnetic 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 of twists 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 oftwists 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 of a 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 ofelectrons from the cath-ode to the ancath-ode, an innovation that subsequently opened the door to the entire electronics industry See Audion; de Forest, Lee; Fleming, John

two tone keyingAmeans ofusing two tones, one for

markand one forspace,to modulate a telegraph sig-nal so as to create two channels transmitting in the same direction

two-phase codingAmeans of increasing 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 trunkA network trunk which operates in -oth directions In the case oftelephone service trunk ines, it refers to one which can be seized from either

nd ofthe connection, as opposed to one-way trunks, hich may be set up to send only or receive only

WPDtraveling-wave photodetector See photodet-ector, traveling-wave tube

_ _ _ _ core

individual fibers

or fiber bundles

secondary conductor

/ insulating layer

I _ _ _ _ conductingcopper wire

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 copper pairs are

en-twined within the sheath) Shielded twisted pair (STP)

looks similar, but has an insulating shield under the

water-resistant sheath The outer sheath is not

neces-sary for all types ofwiring, but is commonly used.

cable suitablefor the higher demands ofdata cables.

Pairs are typically identified by color schemes that

include a solid color and a paired striped wire of the

same color For applications such as Ethernet, the

wires are usually attached to an RJ-45 connector that

resembles a fat phone cable connector.

Lower Middle: Coaxial cable, so-called because two

conductors are housed within the covering, separated

by an insulating layer to reduce crosstalk and to

con-ducting layers touched This is commonly used for

video transmissions.

Bottom: Fiber optic cable based upon

light-guid-ingfilaments rather than electricity-conducting wire.

This is commonly usedforfast digital data

communi-cations.

The three top cables use copperfor the central

con-ducting core.

conducting

water-resistant insulation /

sheath

water-resistant

sheath

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 ABell 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 interferometerSee 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, a filament

(cathode) and a metal sleeve (anode) thatfit over the

filament to attract electrons There was no way to

con-trol electronj1ow It was not until Lee de 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 of300

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

Itwas a pretty exciting development at the time and

a foreshadowing of global network access

Alarge number ofcompanies eventually offered time-share or database information services over TYMNET, including Compuserve, Cybershare, the European Space Agency (ESA), Dow Jones,Dunand 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 ofshared 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/TypexcardAstandardized, compact data card commonly used for modems, memory, and other plugin accessories for computers, digital cam-eras, and more See PCMCIA card, PCMCIAstandards Type 1/Type3 fontThe 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 ifthey 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 1and 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 1fonts 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 ofthousands ofdol-lars and the general public couldn't do much better than to use a special proportional typewriter See Post-Script