Sometimes it is used to send and receive signals over phone lines and for trans-mitting messages or computer data in text form.. At the receiving end, a television set tuner and monitor
Trang 1Fiber Optics Illustrated Dictionary
device-supporting software applications TAPI can be
used to create call control software for telephony
de-vices for computerizing common functions and
sought-after features As an example, TAPI can be
used to create a Caller ID-type function on a
com-puter, with the computer answering a Caller
ID-en-abled phone line, assessing the Caller ID information,
and perhaps relating it to a database of names or other
information associated with the number and logging
the call or notifying the user of the call
Since not all phone systems are equipped with TAPI
interfaces, there are now third parties, such as Ryan
Technologies, that provide protocol conversion
mod-ules that enable TAPI-based applications to link
through the module to the phone system In 1999,
Siemens extended the utility ofTAPI by introducing
a TAPI interface compatible with a national ISDN
terminal This, in conjunction with the Optiset phone,
turns a computer into a powerful telephony terminal
See Telephony Services Application Programming
Interface
Telephony Routing overIP TRIP A policy-driven
inter-administrative domain protocol for routing
voice-over-Internet calls, developed by the IETF IP
Telephony (iptel) working group TRIP is
indepen-dent of the signaling protocol used.Ituses Border
Gateway Protocol (BGP-4) to distribute routing
in-formation between administrative domains It thus
enables digital telephony calls to be routed between
digital network domains and supports the exchange
ofrouting information between providers, thus
build-ing up a forwardbuild-ing information base
In August 2001, TRIP was published as an Internet
Draft and, in September 2001, was submitted to the
IESG for consideration as a proposed standard TRIP
may also be a part of future protocols for the
propa-gation of routing information between gateways and
their associated signaling servers (a process called
gateway registration)
Telephony Services Application Programming
Interface TSAPI A set of guidelines developed by a
group of developers, including Novell, Inc and
AT&T, for interconnecting corporate telephone
sys-terns into the data network server in medium and large
business networks The specification describes the
physical link that can be used to implement
software-based call control from a private branch exchange
(PBX) switch, for example, so that control is handled
from the originating point in the local area telephone
network Thus, TAPI's call tracking capabilities make
it more powerful and suitable for enterprise
environ-ments than the more desktop-oriented Telephony
Application Interface (TAPI) See Telephony
Appli-cation Interface
telephoto, telephotography Visual information
con-veyed through conventional photographs or digital
photographs from data received remotely Journalists,
geographers, navigators, and others use telephotos to
send or receive visual information from remote
sources through wired or wireless communications,
and to print them in various resolutions through
pho-tographic, laser, or other means Satellite photos of
the Earth's surface are extremely popular examples
of telephotos Many of the images now printed in national newspapers are telephotos sent through wire-less modems by journalists using digital cameras and laptops
Teleport Communications Group TCG At one time, a national competitive local telecommunica-tions provider with fiber optic SONET networks in over 50 large markets, acquired in early 1998 by AT&T
teleprinter I Teletypewriter 2 A Western Union trade name for printing telegraph terminals See telex TelePrompt Project A European Community (EC) project funded by a consortium ofacademic and com-mercial groups designed to develop and further tech-nology-based distance learning resources for Euro-pean teleworkers The termteleworkingin Europe is roughly equivalent to the term telecommuting in North America
teleranAnaerial navigational guidance system em-ploying information received through television waves and radar transmitted to aircraft by ground sta-tions
TELESA See Telecom Services Association of Ja-pan
telesales A British term for telemarketing
Teletype A name trademarked by Teletype Corpora-tion for a variety ofteleprinting devices used in com-munications See teletypewriter
Teletype CorporationAn early printing telegraph company, the Morkrum-Kleinschmidt Corporation, which was acquired in 1930 by the Bell System and renamed Teletype Corporation
teletypesetter A machine for remotely controlling typesetting machines When these were originally put into service, teletype machines relied on a five-unit code that was insufficient to transmit all the charac-ters needed by a similar teletypesetting machine Thus, a six-unit signal code was developed for teletypesetters to increase the size of the character set from 32 to 64
teletypewriter TTY A printing apparatus which, in its common form, resembles a typewriter on a ped-estal with continuous feed or tractor feed paper so that
it can print unattended Sometimes it is used to send and receive signals over phone lines and for trans-mitting messages or computer data in text form The teletypewriter superseded key and sound tele-graph systems because it could operate unattended,
be read by individuals without knowledge of Morse code, and achieve transmission speeds of 60 to 100 words per minute The earliest teletype-style print-ers and start-stop synchronization methods were de-veloped by Charles and Howard Krum See Baudot code; Krum, Charles and Howard; telegraph, print-ing; Teletype; telex
teletypewriter code A five-unit code that employs elements ofuniform length Start and stop pulses are used to distinguish each character in the transmis-sions See Baudot code
teletypewriter exchange serviceAny commercial service which provides teletypewriter
Trang 2communica-ing exchange Similar in concept to a long distance
telephone exchange TWX is one such service of the
Bell System, established in 1931, subsequently
owned by AT&T See Telex
Compact Television Camera
A tiny television camera, not much bigger than a
human hand, designed in the days when television
cameras were large and heavy The technology was
designedfor the demanding task ofspace observation
and very long-distance communications by the
Marshall Space Flight Center Similar cameras were
quickly adaptedfor commercial telecommunications.
[NASA/Marshall Space Flight Center image detail,
date unknown.]
televisionTV A system of sending and receiving
transmission isn't moving), usually in conjunction with sound, although some closed-circuit television systems don't include sound circuitry Television broadcasts can be transmitted through air or over cables, with cable TV (CATV) increasing in popu-larity Air transmissions are captured with a televi-sion antenna designed for a portion of the broadcast spectrum (although three-in-one antennas exist for UHF, VHF, andFMsignals) At the receiving end, a television set (tuner and monitor combined), or a VCR tuner and monitor are typically used to display the broadcast
television broadcast bandThe various frequencies which are assigned and regulated for television broad-cast transmissions Due to the proliferation of pro-gramming and the increased availability of access through satellite transmissions, there is constant pres-sure to increase available frequencies and channels, and hundreds of programming channels are now available See band allocations for a chart
television cameraA lens-equipped, optical-sensing pickup device designed to capture moving images and transmit or pass them on to receiving, editing, and broadcast equipment The type ofsignal generated by the camera varies according to the receiving or edit-ing equipment, and varies from country to country Television cameras have traditionally been expensive, large, heavy, analog, high-resolution apparatuses This is all changing, with small handheld digital and
Common Television Broadcast Formats
National Televisions Systems Committee NTSC The North American standard since the 1950s
525 vertical lines NTSC uses negative video modulation and FM sound
Phase Alternate Line PAL The predominant standard in the United Kingdom
and parts of Western Europe since the early 1960s
625 vertical lines There are a number of variations of the PAL system, including PAL-B, PAL-H, PAL-M, etc PAL uses negative video modulation and FM sound
Sequential Color and Memory SECAM Developed in France and used in North Africa,
Russia, and parts of Europe since the early 1960s
625 vertical lines There are a number of variations of the SECAM format, including SECAM-B, SECAM-H, etc
High Definition Television HDTV Introduced in Japan and proposed as a global
standard, but not readily adopted by American and other manufacturers, some of whom would prefer
to enhance current standards rather than adopt a new one 1125 vertical lines at 60 frames per second HDTV is supported by some Internet push channels and can be viewed with an interface peripheral and a computer with a fast connection Multiplexed Analog Components C-MAC Developed in the U.K and recommended by the
EBUas a European standard
Trang 3Fiber Optics Illustrated Dictionary
analog personal cameras beginning to rival the
qual-ity of traditional TV cameras for only a fraction of
the price See NTSC, PAL, SECAM
television history Television, perhaps more than any
other of the major communications technologies,
arose in fits and starts in the late 1800s with many
geographically diverse announcements ofsuccess and
few demonstrated working systems One of the
im-portant discoveries in the history of television was
the photoconductive characteristics of selenium,
which responded to the amount of light hitting the
surface AFrench researcher, M Senlacq, suggested
in 1878 that selenium might be used to register the
shapes of dark and light areas on documents British
researcher Shelford Bidwell was able to successfully
transmit silhouettes by 1881, and the now famous
German inventor, Paul Nipkow, after whom the
Nipkow disc is named, patented an
electromechani-cal television system in 1884 But the transmission
of moving images and shades ofgray in high enough
resolutions to be practical eluded the early inventors
Although patents for television-related technologies
began to appear in the late 1800s, it was not until the
1920s that television transmission and reception as
we know it was demonstrated by inventors such as
JohnL.Baird in the west and Kenjito Takayanagi in
Asia Baird's first significant success was in 1926,
the same year Tekayanagi transmitted Japanese script
with a cathode-ray tube
In the U.S., a precocious 15-year-old, Philo T
Farns-worth, described an idea for a television to his
school-mates and reportedly showed a sketch to his teacher
in 1922 In 1927 he succeeded in building a working
model
Experimental television stations sprang up in the late
1920s and, by the mid-1930s, regular public
broad-casting began to develop In Europe, television
im-ages were being transmitted by 1931
Television sets were available by the late 1930s, but
it took time before the technology became affordable
for home use By the late I940s, there were at least
20 broadcast stations in North America, with hundreds
of hopefuls clamoring for the limited licenses
Black and white televisions came into widespread use
in the 1950s in North America and color television
was common about 15 years later By the mid-1980s,
melon-sized portable televisions became inexpensive
and wrist-sized consumer TVs had been developed
Commercial sponsorship provides much of the
fund-ing for television in North America, thus controllfund-ing,
to some extent, the type of programming which is
available, influenced by majority consumer demand
or perceived viewer preferences.Inmany other
coun-tries, television is funded and controlled by local
gov-ernments
The next major step in television broadcasting was
the launching of communications satellites such as
the Telstar 2 in 1962 which permitted
intercontinen-tal communication Commercial application of
sat-ellite television broadcasting was pioneered by the
Canadian Broadcasting Corporation through the
ANIK satellite in 1972, followed in the late 1970s by
Turner and the Public Broadcasting System (PBS) in the U.S
In North America, satellite television broadcasts can now be received by consumers on small parabolic dishes that are served by monthly subscription ser-vices, with hundreds of potential stations available Television is widely used for mass-media entertain-ment, education, distance monitoring, and local se-curity monitoring
The influence of television on world culture is sig-nificant and substantial, with a preponderance of the programming originating in the United States Thus, the role models depicted through television program-ming and advertising sponsors have a strong effect
on viewers, and implicitly promote American values, styles of dress, and cultural priorities to all parts of the globe See Baird, John Logie; Farnsworth, Philo T.; Nipkow, Paul Gottlieb; Nipkow disc; Takayanagi, Kenjito; television; television camera; Zworykin, Vladimir
television relay A station designed to pass on a tele-vision broadcast signal to the next station so the sig-nal is protected from loss The relayed sigsig-nal is not intended for reception by viewers until it reaches the destination station
television signal The coding of images can be accom-plished in a number of ways, and there are several standards, each of which is preferred in a different part of the world Common formats related to the broadcast and display of moving image signals are shown in the Common Broadcast Formats chart telework Work at home or at satellite locations made possible through computer and telecommunications technologies In 1988, Jack M Nilles proposed a broad definition of telework as " all work-related substitutions of telecommunications and related in-formation technologies for travel," thus, employerl employee interactions across distance through new technologies This term is more common in Europe and is roughly equivalent to the termtelecommuting
in North America See ADVANCE Project, European Community Telework Forum, TelePrompt Project telex teleprinter exchange Generic term for a com-munications service developed near the end of the second world war that uses teletypewriters to trans-mit through wire lines and automatic exchanges to produce a wlitten message at the destination In Eu-rope, this technology used audio frequencies over phone lines See Baudot code, Telex, Western Union Telex A global message service established in the United States by Western Union in the early 1960s This was competitive with AT&T's TWX service Telkes, Maria A physicist who did pioneer work in the development of solar energy in the early part of the 20th century Solar energy has subsequently be-come an extremely important power source for or-biting communications satellites
Telnet Protocol A widely supported 8-bit, byte-ori-ented network protocol for remote terminal access, originating from the days of the ARPANET Telnet allows the user to log on to another system through a
TCP/IPnetwork, and perform file functions and other
Trang 4as a command to launch a remote utility that uses the
Telnet Protocol The form ofthe Telnet command is:
telnet [IP_address/host_name] [port]
(with the command entered in lower case) See
RFC 318, RFC 854, RFC 855 to RFC 861 (various
options)
TELSTAR 1A historically significant low-altitude
communications satellite that broadcast microwave
transmissions and tracked satellites in the 1960s This
AT&T endeavor is claimed to be the first active
com-munications satellite, launched 10 July 1962 by the
United States, although some RCA engineers
launched a transmissions satellite earlier It is the first
transponder-equipped satellite Prior to this, satellites
were passive transmitters, but the use oftransponders
for amplifying the signals was preferred from this
time on, and some satellites now include as many as
ten transponders The TELSTAR had some early
problems that were fixed in 1962; it ceased
function-ing in 1963 By 1964, two more TELSTAR satellites
had been successfully launched and TELSTAR 3-D
was launched in the mid-1980s
Telstar Communications Satellite
The Telstar 3-D satellite being put into Earth orbit
from the payload bay ofthe Space Shuttle Discovery
in the mid-1980s [NASA/JSC image detail.}
TEM wavetransverse electromagnetic wave
template 1 A pattern, guide, table, or mold used to
provide the basic configuration, format, or design for
creating a new version, or multiple versions of a
project with few or no changes Atemplate is intended
to save time by automating the creation of new
ver-sions Aword processing template can be used to set
up documents which are reissued frequently with only
minor changes (e.g., form letters)
Temporary Mobile Station IdentifierTMSI A
dy-namically assigned mobile station identifier (MSID)
TENETSee Texas Educational Network
tensile strengthA descriptor for the greatest amount
of longitudinal stress that can be borne by a
particu-lar material before it will rip apart The units used to
describe this property vary from industry to
indus-try.It is an important factor in many manufacturing
and industrial applications
sion parameters in a newly spliced fiber optic cable assembly This is often sold as an option to a clad-ding alignment splicer See cladclad-ding alignment splicer
tera-T A prefix for an SI unit quantity of 1012
, or 1,000,000,000,000 It's a trillion, a very large quan-tity, but considering there are now hard drives with terabytes ofstorage space, it's not as big as it used to
be It comes from the Greek rootteratorteras mean-ing "monster." See peta-, pico-
TERENATrans-European Research and Education Networking Association AEuropean network evolv-ing from the European Academic and Research Net-work (EARN) and the Reseaux Associes pour la Re-cherche Europeenne (RARE) TERENA was estab-lished from the merger ofthese organizations in 1994
to promote and participate in the high quality inter-national information infrastructures to benefit re-search and education TERENA includes members from more than three dozen countries, as well as a number ofhigh-profile computer developers/vendors, and the CERN and ACMWF international treaty or-ganizations
TERENA has been responsible for BITNET support
in Europe including data collection and the distribu-tion of nodes and routing tables See BITNET
terminal1 An endpoint, extremity 2 A conducting device, often a small metal post or receptacle, pro-vided for facilitating a good electrical connection
3 A device or system which provides remote access
to a central computer 4.Anendpoint in a communi-cations line, or one which can be, but is not neces-sarily, extended to other circuits
Terminal AdapterTA A device available in vari-ous configurations from a number ofvendors, which provides protocol adaptation and interfacing with an
Terminal Endpoint IdentifierTEl An identifier for distinguishing between several different devices us-ing the same ISDN transmission links Values may
be dynamically assigned to TEIs ranging from 0 to
126 Fixed TEIs are assigned values between 0 and
63 The value of 127 is reserved for TEl broadcast, which aidsincarrying out management functions.An ISDN device must be assigned at least one unique TEl value, either by preassignment or dynamically, by the local exchange, as needed (sometimes called Auto TEl) The TEl Management Protocol is used to dy-namically assign values in a request/response inter-action Dynamic allocation is usually used on point-to-multipoint links but may be used on point-to-point links
terminating officeIna transmission such as a phone call or telegraph message, the terminating office is the switching center which is the final one that con-nects directly to the subscriber line or other receiver ofthe communications In Internet dialup communi-cations, the local ISP would be considered the termi-nating office
Trang 5Fiber Optics Illustrated Dictionary
TERMITE A terminology database which contains
all tenns appearing in printed glossaries of the
Inter-national Telecommunication Union (lTD) since 1980,
contributed by a variety of industry professionals,
including technical editors and translators English,
French, Spanish, and Russian source tenns are
in-cluded Access to the database is available through
Telecom Infonnation Exchange Services (TIES)
ITU activities are now also being archived in this
database http://www.itu.int/search/wais/Tennite/
terminator A physical device or setting to indicate
the end of a data path in a connection in which more
devices may be added.Ifa chain is not terminated,
the end of the system is seen as an open port and the
system either continues totryto send signals to (and
to expect signals from) another device that isn't there
or, in fiber optic networks, to experience undesirable
back reflection and instability
SCSI-format cartridge drives sometimes have
autotermination built in to the device and the user may
have to use a specified port on the device, if it is the
last in the chain Some devices tenninate internally
with a setting on a switch or a small internal or
ex-ternal dipswitch Other devices, such as scanners and
external hard drives, are terminated with an external
tenninator attached to one of the SCSI input/output
connection mounts Internal hard drives are often
ter-minated with a set of resistors that can be removed
or, in some cases, with jumpers
Most SCSI chains can be tenninated with standard
50- or 68-pin SCSI tenninators, but there are
excep-tions, including a proprietary "black" SCSI
tennina-tor distributed by Apple Computer for some of their
older computers and certain Apple laser printers that
support font storage on attached hard drives
On an Ether network using "thin" cables (1 ObaseT),
a tenninator is required on each end of the data bus
if the chain or "ring" is not closed If "thick" Ether
(1Obase2) connections to a plug-and-play hub in a star
topology are used, separate tennination is not
re-quired
In a wired network, devices such as SCSI-fonnat
CD-ROM drives, hard drives, and scanners can be chained
along the same data path, but a tenninator is required
on the end device (usually the one farthest from the
motherboard) to prevent the system from seeking
devices beyond the last one Failure to terminate a
SCSI chain can cause immediate or sporadic
prob-lems with data access on the chained devices In a
fiber optic network, the problem of back reflection
can be even more serious than in wired networks
Many aspects of wired networks are designed to
handle signals in two directions along one wire Even
when separate wires are used, the strength ofthe data
signal is controlled such that damage to components
is unlikely (possible, but not common) In fiber
op-tic networks, an open, untenninated port may allow
laser light to escape, which can be a danger to eyes
Improper closing of a fiber port can result in the
la-ser light being reflected back down the waveguide
in the wrong direction This not only disrupts the path
and amplitude of the light data signals, but also may
interrupt or damage the laser source
Passive tenninators are most common, but advance-ments in networking and greater demands on the tech-nology are giving rise to various types of active ter-minators Longer cable runs and higher data rate per-fonnance may be accompanied by higher noise sen-sitivity that may be mitigated by active tenninators with voltage regulation Active SCSI tenninators may autoselect between low-voltage differential (LVD) and single-ended (SE) modes Because of the extra electronics, active tenninators are sometimes a little larger than passive tenninators commonly cost about 50% more than their passive counterparts
Fiber optic tenninators come in a variety of fonnats, including SC and FC and generally follow Telcordia standards Some fiber tenninators are doped and are typically sold to support specific wavelength ranges Many ofthem resemble standard fiber connectors but they are designed to eliminated back reflection rather than to facilitate the attachment of another length of cable or device
Terrestrial Digital Service TDS Acommercial pri-vate digital data transmission service offered by MCI
to subscribers over local exchange carrier (LEC) TI, DS-3 systems Thus, customers would have fast trans-mission links to MCI Services There was some de-bate over this service option through the Federal Communications Commission (FCC)
TESe Technology Subcommittee
tesla Ameter-kilogram-second unit ofmagnetic flux density equivalent to one weber per square meter Named after Nikola Tesla
Tesla coilAnair-core transfonner for creating high-voltage discharges at very high frequencies Tesla, Nikola (1856-1943)Anengineer and inven-tor born in Smiljan Lika (Austria-Hungary) who de-veloped the alternating current induction motor, an essential part of alternating current distribution sys-tems Tesla began his research in Hungary, and then emigrated to the United States in 1884 He created a number ofunique inventions and also improved upon those of others
In America, Nikola Tesla and Thomas Edison came into regular contact with one another, not always with happy consequences, and an enmity grew between the two men When it was proposed in 1912 that the Nobel prize be awarded jointly to Edison and Tesla, Tesla eschewed any association with Edison, and the prize went to a Swedish scientist instead
Tesla's inventive mind turned power generated de-vices into interesting applications such as aircraft power systems and robotic submarines In 1888, he was awarded a patent for an electromagnetic motor Tesla eamed more than 700 patents in his lifetime and produced many more unpatented ideas and inven-tions
Tesla was somewhat temperamental and eccentric One of his most practical contributions was the ad-aptation of alternating current into everyday appli-cations His colleague, George Westinghouse, further implemented many ofTesla's ideas The tesla unit of magnetic flux is named after him
Trang 6test boardA switching panel used for making
tem-porary connections in conjunction with the panel or
equipment being tested By diverting some ofthe
sig-nals through the test panel, problems can sometimes
be more easily isolated or identified A test clip can
also be used for the purpose ofmaking quick
tempo-rary connections See breadboard, shunt
test jack/plugAconnecting hole in a circuit or panel
for inserting a corresponding plug Gack) and cable
for making temporary connections for testing and
maintenance Test jacks and plugs come in many
shapes and sizes depending upon what type of
cir-cuit is tested A telephone test set is a portable
tele-phone handset that has clips for temporary
attach-ments to a conducting line or test jacks for
tempo-rary insertion into in a test jack plug frame
test jack frame TJF In private branch exchange
(PBX) telephone systems, a frame for inserting test
cables for maintenance and testing, usually mounted
in or near the main PBX cabinet and terminating the
cabinet connections
test patternAny pattern generated for a particular
transmission medium that indicates the integrity of
the various characteristics of its signal, which may
include resolution, signal strength, stability,
linear-ity, contrast, brightness, colors, sound range and
qual-ity, etc 2 In video editing, a series of bands of
spe-cific colors 3 In television broadcasting and
televi-sion set calibration and diagnosis, a pattern (known
to some as the Indian head pattern) which includes
particular lines and line widths, ellipses, tonal
gra-dations, and numerical values that allow the
diagnos-tician to determine problems and make adjustments
This test pattern was frequently used in the 1950s and
1960s by local stations as a visual signal to viewers
to indicate that there was no programming currently
in progress, although this use has greatly declined due
to the multitude of programming now available
tetrodeA four-element vacuum tube The
three-ele-ment tube, called a triode, was developed by Lee de
Forest This no doubt inspired experimenters totry
other configurations The four-element tube followed,
consisting of a filament, plate, and two grids rather
than one The second grid, the tetrode or screen grid,
was positioned between the first grid and the
elec-tron-attracting plate (anode)
Texas Educational NetworkTENET ATexas
edu-cation communiedu-cations infrastructure dedicated to
fostering educational innovation and excellence
among educators and students TENET developed
through the collaboration of the Department of
In-formation Resources, the Texas Education Agency,
and the University of Texas TENET provides
vari-ous resources, including publications, discussion
fo-rums, and professional development seminars and
facilities http://www.tenet.edu/tenet-info/main.html
TFTSee thin film transistor
TFTPSee Trivial File Transfer Protocol
TFTP Multicast OptionA protocol option for the
Trivial File Transfer Protocol (TFTP) to enable
through multicast packets to increase network effi-ciency TFTP Multicast Option was submitted as an Experimental RFC by A Emberson in February 1997 See Trivial File Transfer Protocol, RFC 2090
thereminAnelectronic musical instrument incorpo-rating radio frequency oscillators in which two simi-lar frequencies were combined to provide a lower, human-audible frequency This was done by combin-ing a reference frequency with a variable frequency The theremin was played by interposing a hand to vary the capacitance between two projecting elec-trodes, thus controlling the pitch and volume.Itwas first constructed in 1920 and became popular in the late 1920s
The process of mixing signals of slightly different frequencies is called heterodyning and was incorpo-rated into many radios over the next couple of de-cades A transistor version of the theremin still ex-ists' and Mystery Science Theater 3000 fans are fa-miliar with its eerie sounds
Itwas named after its inventor Leon Theremin, who originally called his invention an "retherphone." See heterodyning, Theremin, Leol1'
Theremin, Leon(1896-1993) A Russian engineer and inventor who devised electronic musical instru-ments, most notably the "retherphone" (theremin) while a student at the University of Petrograd He traveled to America in 1927 to playa concert, and 2 years later licensed the Radio Corporation ofAmerica (RCA) to manufacture a "thereminvox." While in the U.S., Theremin also experimented with multimedia concerts, combining light shows and dance with the theremin music, later returning to do research at the University of Moscow See theremin
thermal noiseRandom noise arising from heat gen-erated by the motion of charged particles Thermal noise in electrical circuits is undesirable if it inter-feres with transmission
thermal circuit breakerA breaker mechanism that trips when heat generated by excessive current ex-pands the conductor See circuit breaker
thermionAn electrically charged particle (a positive
or negative ion) emitted from a heat source See ther-moelectron
thermionic emissionThe emission of electrically charged particles under the influence of heat
Ther-mionic emissions are characteristic of hot
cathode-ray tubes Cathodes without thermionic emissions are
called cold cathodes.
thermionic valveSee vacuum tube
thermistorAn electrical resistor comprising a semi-conductor with a high, nonlinear temperature coeffi-cient The resistance ofthe semiconductor varies suf-ficiently in relation to the temperature to make it use-ful in a number of applications See thermostat
thermocouple, thermal junctionAdevice that mea-sures temperature at the junction of a pair ofjoined wires employing dissimilar materials, with the dif-ference in potential proportional to the temperature, determined by an instrument connected to the other ends of the wires
Trang 7Fiber Optics Illustrated Dictionary
Semiconductor thermocouple assemblies are
fabri-cated by connecting two dissimilar metals and
inter-connecting the thermocouples in series Materials
with a high thermoelectric coefficient are typically
used (e.g., antimony) When the junctions are
dissimi-lar (e.g., different metals), the difference in heat
ab-sorption can be used to generate voltage, thus
signal-ing the detection of heat Treatsignal-ing one of the metals
to increase its absorption through chemicals or
col-oring may magnify the effect (improve
signal-to-noise ratio) See potentiometer; pyroelectric
detec-tor; Seebeck, Thomas; thermopile
thermocouple wire Awire used with a thermocouple
which is made of iron or particular alloys calibrated
to the appropriate specifications
thermodynamicsThe art and science ofheat-related
phenomena, their properties and relationships
thermoelectronAn electron (negative thermion)
emitted from a heat source See thermion
thermography A printing process in which
nondry-ing inks are treated to simulate a raised, engraved
surface After passing through the press, the ink is
dusted with a compound which, after the excess is
removed, is exposed to heat, causing it to fuse with
theinkto form a raised surface
thermopile Acomponent with broadband absorption
characteristics suitable for detecting radiation such
as infrared light Thermopile detectors are fabricated
from multiple thermocouple devices connected in
series They may be made with wired junctions or
film junctions, with film versions generally
provid-ing advantages ofsize, portability, and response times
over larger wired assemblies See photodetector,
ther-mocouple
thermoplasticAmaterial with industrial significance
because it can be heated and reshaped and rehardened
by cooling It has various uses including insulating
and information recording Contrast with thermoset
thermoset A resin or plastic material which can be
shaped and cured, but once this has been done,
can-not be reshaped and cured again, as with
thermoplas-tic Contrast with thermoplasthermoplas-tic
thermostat1 A sensing and regulating device
trig-gered by temperature which is useful in turning
ma-chines on or off, for controlling fire safety devices
such as alanns and sprinklers, and for regulating
heat-ing and coolheat-ing systems 2 A device which regulates
temperature, by measuring it and controlling heating
equipment (or heating and cooling equipment) in
or-der to maintain the temperature at the setting selected
on the thennostat This is usually accomplished by
triggering the heating circuit when the temperature
varies a certain amount below or above the desired
setting Thermostats that can be programmed for
spe-cific temperatures at scheduled times during the day
are increasingly common Temperature regulation
(cooling) in large supercomputing implementations
is important See thermistor
THF See tremendously high frequency.
thin film A very fine layer or combined layers used
to enhance or change the properties ofa material Thin
films are typically "grown" in chemical vapor
deposi-tion processes There are many different types offilm and their structure depends upon the chemicals used, the properties and combination ofthe component lay-ers, temperature, and other fabrication parameters Thin films can be grown with low dielectric constants, making them suitable for use in integrated circuits and
as filters (e.g., DWM ONU filters)
Magnetic thin films have unusual megnetotransport properties useful for the development of sensing de-vices and magnetic recording technologies Thin films can be grown at high temperatures for use in superconductivity research
Thin films have thousands of applications as filters, dielectric mirror surfaces, barrier layers, polarizing layers, and more Thin films can be deposited on fi-ber optic filaments to filter a signal or prevent backreflection Antireflecting coatings for optical lenses in eyeglasses and imaging devices can be made with thin films Calculators and wristwatches use sili-con thin-film solar chargers
Traditionally, thin film-treated wafers were placed be-tween fiber endfaces to filter the light crossing from one fiber to the next However, it has been suggested that better performance is possible by stacking be-tween 20 and 150 layers of alternating highllow re-fractive-index films onto a substrate and using this thin film component in place of treated wafers See sputtering See Fiber Optic Probes diagram
thin film transistorTFT A technology used in dis-play devices which creates a correspondence between
a transistor and pixel on the screen so that pixels can
be independently controlled Used in color (RGB) active matrix LCD panels This technology has been applied to portable display projectors and similar devices
Thompson, Joseph John(1856-1940)AnEnglish experimenter who investigated electricity and X-rays
He was awarded a Nobel prize in physics in 1906 for gaseous conductivity of electricity
Thompson, Ken (1943- ) Principal developer, along
with Dennis M Ritchie, of the Unix operating sys-tem in 1969 It is quite a distinction considering its widespread use and utility Unix has since evolved through extensive support by the programming com-munity and exists in a variety of forms, although all bear similar features Thompson also authored B, which was a predecessor to C See Unix, UNIX
Thompson, WilliamSee Lord Kelvin
Thomson, Elihu (1853-1937) Inventor ofone ofthe
first alternating current (AC) generators, in 1878 At the time, the predominant form of power was direct current (DC) This was a significant achievement be-cause it enabled the transmission ofmuch higher volt-ages, necessary to cross some ofthe distances desired Improvements to the concept were soon developed
by William Stanley Thomson also experimented, in
1892, with electric arcs He collaborated with Sebastian de Ferranti and William Stanley in the development of the transformer
thread 1 In piping, a helical indentation used to match and secure separate sections 2 One ofa num-ber of continuing elements, themes, or trains of
Trang 82110 2120
Figures 27a - 27cfrom a patent developed by M Wach et al show different views ofa fiber optic light-scattering probe consisting ofa tightly aligned multifiber ring sUlTounding a central fiber Stepped index silica core/cladding fibers are suitablefor this type ofdevice The centralfiber, insulated by a light-bloc/dngfilm or coating, may be used
to deliver light while the surrounding ringfibers detect it or vice versa Figure 80 illustrates the application of thin-film filteringto a complex contoured suiface (in this case the cone-shaped endface ofa fiber filament that is coupled with anotherfiber) Filters such as the one illustrated in Figure 80 can help reduce back reflection at coupledjoints Index-matching epoxy or gel can be used to fill in the gap between fibers
.z!!!jz'- 55 E
Figures 55a - 55e illustrate how different configurations are possible for manipulating light through adjoining segments ofa multifiberprobe Various endface polishes, angles, and thin film filters make it possible to use the basic idea in a variety ofapplications [Diagrams adaptedfrom USPTO patent#6,416,234,submitted August 2000.J
Trang 9Fiber Optics Illustrated Dictionary
thought related to a common forerunner 3 In
pro-gramming, a flexible process organization
mecha-nism by which individual processes can use common
resources, but continue to operate unimpeded by other
threads, if needed, in order to improve program
effi-ciency or to increase simultaneous access to various
system or applications resources Common in
object-oriented systems
thread, discussionIn online newsgroups, a topic of
conversation characterized by the same (or similar)
subject line, and theme and direction of discussion
Threads are a very convenient way to follow one line
of thought through the myriad opinions discussed in
the general context of a newsgroup Good
newsread-ing software will organize threads into groups and
subgroups much the same way computer directories
(folders) are organized on the computer operating
system Thus, the user can selectively open and read,
or close and ignore, a thread
three finger saluteslangA descriptive phrase for
rebooting the operating system (without powering
down the system) with three designated keys held
down simultaneously for MS-DOS/lntel-based
IBM-licensed systems (Ctrl-Alt-Delete) and Amigas
throughputProduction; output; nonredundant
infor-mation or items of relevance moving through a
sys-tem Throughput is used in industrial and computing
industries to describe the efficiency of a system or
end-result of a communication (how much
infonna-tion got through)
The measurement of throughput is quite specific to
the system and infonnation or objects being
trans-ferred, so there are few generalized standards for time
intervals or total data against which to compare the
throughput (end result) Nevertheless, relative
mea-sures of throughput, as compared to another
manu-facturer, another type of machine, or when processed
in a different manner, can be very useful in tuning a
production line system Relative measures of data
throughput in different parts of a network, or over
different data protocols or operating systems,
simi-larly can be used to improve the configuration and
efficiency of a computer network
TI-99/4A Texas Instruments home computer
intro-duced early in 1980 It featured 16 Kbytes RAM,
sound capabilities, 16-color graphics on a 13-inch
color monitor, extended TI BASIC, and cartridge-like
solid state program modules for a list price of$1150 U.S
TIASee Telecommunications Industry Association
TillSee tone in band
TICSee Token-Ring interface coupler
ticketIn telecommunications, a record of a
transac-tion or paid toll, fare, or fee The ticket indicates
ei-ther that the transaction has been confinned and it's
OK to bill the client, or that the transaction and
bill-ing have both taken place (as in many credit card
transactions) Tickets traditionally were on paper, but
electronic tickets are becoming prevalent, with online
transactions sometimes going directly through to the
credit card company from the vendor without any
slips or other paper confinnations
tickler Incomputer applications, a program designed
to hibernate until a certain time or until certain events take place, and then become active to remind the user
of something timely or important, such as appoint-ments, anniversaries, events, etc These applications have variously been called ticklers, reminders, and naggers
tickler, electronicInelectronics, a feedback or re-generation device consisting of two small coils con-nected in an electron tube, one to the anode (in se-ries), the other to the grid-circuit
tien.Fastener, electrical strap, bundler A strip, usu-ally of plastic or Velcro™, to hold wires away from one another, bundle them together, or fix them in place, sometimestoa post or other secure structure
tie line I In power systems, transmission lines that connect neighboring systems 2 In telecommunica-tions, a line for directly tying two telephone or tele-graph connections together without going through a public switching center, often called a "dedicated" line For example, the President might have a tie line connected directly to top advisors that doesn't go through any outside switches or connections, to en-sure security, reliability, and speed for the connection
In the days before telephone switching centers and central offices connected local telephone subscribers, tie lines were common For example, in the 1800s, a dozen telephone or telegraph tie lines might be wired out of a single office to connect it with other local businesses The streets were often cluttered with hun-dreds of lines running between windows and build-ings and the utility poles holding the lines were com-plexly wired and difficult to maintain
Tie lines are still used for a variety of security and business-related purposes They are especially use-ful in office complexes composed of several build-ings that have a large volume of calls between the buildings Atie line may be set up to connect directly simply by lifting the handset or pushing a button, as
in a hot line Atie tmnk connects to telephone
switch-ing systems such as two private branch exchange (PBX) systems and may require dialing access code prefixes reserved for that purpose on a particular sys-tem or the syssys-tem may be locally automated to inter-pret an extension number to be translated into a tie line call
With the evolution of voice over digital data net-works, the concept of tie lines has been adapted to computer networking Access concentrators can be used to consolidate separate voice and data lines used for communications within a company into a single network and voice over network communications can then replace traditional telephone tie lines Thus, ex-isting Frame Relay links used for data, for example, could also be used for voice communications, remov-ing the need for dedicated phone lines
tietrunk Atelephone (or telegraph) line directly con-necting private branch exchanges (PBXs) See tie line
tie line control systemIn power distribution, a sys-tem for administering the amount of electrical energy purchased by a subscriber (usually an industrial com-plex) from a utility company
Trang 10material used for holding together a bundle ofcables
for ease of placement or movement as a unit Plastic
tie wraps sometimes have a hook mechanism that
catches and holds the tie when it is cinched tight
Velcro brand tie wraps are easy to unwrap and
read-just, if needed
TIES 1 Telecom/Information Equipment and
Ser-vices A government-to-government program which
providesu.s.and Russian support for the expansion
of international commerce in high technology This
is a subgroup under the U.S.-Russia Business
Devel-opment Committee (BDC) 2 See Telecom
Informa-tion Exchange Services
TIFFTag Image File Format A very widely used
platform- and application-independent, lossless,
color, raster image file format that encodes the data
as strips or bands The TIFF format is used in faxes,
image processing programs, scanned files, and many
graphics creation programs.Itis well supported by
service bureaus and the printing and graphics design
industries Files are often identified by the TIF or tiff
file extensions
Creation of the format took into consideration the
needs of the desktop-publishing industry and other
related graphics applications, with the goal of
mak-ing image information broadly interchangeable TIFF
was created to be extensible so that it may
accom-modate future needs
TIFF has gone through a number of major revisions
but, in general, fields are identified with unique tags
so that various applications can elect to include or
exclude particular fields depending upon their needs
and capabilities The core fields comprise BaselineTIFF
ATIFF file consists ofthree main parts: an image file
header, a directory offields, and the file data
Descrip-tions and definiDescrip-tions of baseline and extended fields
are documented in the TIFF Technical Notes (TTN)
Anadaptation called TIFF-FX has been defined for
facsimile applications See facsimile, scanner,
TIFF-FX, TWAIN
TIFF-FXA subset of TIFF adapted to generating
documents with minimal, lossless grayscale and color
attributes for use as facsimile messages The format
uses some of the Baseline TIFF fields in addition to
extensions pertinent to facsimile transmissions Since
the format can be used over both traditional and
host-based transmissions media, TIFF-FX is suitable as a
downwardly compatible, standardized facsimile
for-mat for data network communications ProfileS
(TIFF-S) is a subset ofTIFF, related to TIFF-FX, that
defines a minimal black-and-white format to enable
fast easy transmission ofsimple facsimile documents
Profile F(TIFF-F) is a slightly extended version of
Profile S that is still restricted to black-and-white
transmissions TIFF-F was originally introduced by
Joe Campbell and a group of fax experts; then, in
1998, with increased interest in Internet faxing
con-nectivity, it was formally described by the IETF
In-ternet Fax Working Group
Inessence, the imagedatato be faxed are compressed
and inserted into a TIFF-FX file with the
informa-The byte order is from least to most significant (an important detail, since the full TIFF specification can
be set to either big- or little-endian and conversion may be necessary before transmitting as a TIFF-FX variant) While the full TIFF specification is some-what flexible in terms of the ordering and structure
offields, TIFF-FX recommends that multiple image file directories(IFDs) be organized as a linked list The MIME Content Type for these files is image/tiff The Application parameter is TIFF-REG (optional) See IFax device, image file directory, TIFF, RFC 2301, RFC 2306
TIIAPSee Telecommunications and Information Infrastructure Assistance
tiling 1.In printing, a technique for printing a large image on pieces of paper that are small, relative to the size ofthe image Commonly used for billboards, banners, and wall-sized murals Most computer print-ers have options for tiling, in order to print large im-ages on letter sized paper.2.Indigital image display,
a visual artifact common to heavily compressed im-ages which causes a blocky, mosaic-like appearance
to otherwise smooth lines and transitions See DCT, JPEG
tilt lockingA method of frequency-locking a laser beam to an optical cavity by misaligning the laser with respect to the resonating cavity such that a non-resonant spatial mode is produced.Anassessment of the interference between the carrier and the spatial mode yields a quantum noise-limited frequency dis-criminator Tilt locking uses interference between the carrier field and a directly reflected phase reference signal (e.g., a non-resonant higher-order spatial mode) Thus, the encoding/decoding ofspatial modes
is optical rather than electro-optic
Interference between the two spatial modes may be assessed by detecting the reflected beam on a two-element split photodiode such that each lobe of a transverse electromagnetic (TEM) mode is incident
to a separate side of the photodiode The error signal
is derived by subtracting the photocurrents from each side of the photodiode
Tilt locking may be useful for frequency stabilization, conversion, or interferometric gravitational wave detection
TIMASee Interactive Media Alliance, The TIMETime Protocol Anetwork date/time protocol submitted as an RFC in May 1983 by Postel and Harrenstien TIME provides a site-independent, ma-chine-readable date and time The Time service pro-vides the time in seconds since midnight January 1,
1900.This is useful for systems that do not have a built-in date/time clock and for systems that need to
be coordinated to preserve or aid data integrity or pro-cess administration TIME can be acpro-cessed through port37over Transmission Control Protocol (TCP) or over the User Datagram Protocol (UDP) See RFC 868
time codeA system of encoding timing information
on a recording medium, usually along with the information that is being stored This technique is