galvanometer Named after Luigi Galvani, an instru-ment for detecting low levels of electric current through the use of a magnetic needle or coil sus-pended within a magnetic field.. The
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GAC See Global Area Coverage
gadolinium A light, silvery, crystallizing,
ferromag-netic rare earth metal isolated from yttrium in the late
1800s Gadolinium has been used in the production
of phosphors in color cathode-ray tubes (CRTs), and
for making gadolinium yttrium garnets used in
mi-crowave technologies See europium, yttrium
gaff The spike that is attached to a utility pole
climber's iron See boomer
gage Performance indicator See gauge
Gaia Global Astrometric Interferometer for
Astro-physics See interferometer
gain Increase in power of a transmission, usually
in-dicated in decibels (dB) when applied to audio gain
Gain is sometimes intentionally created by using
vari-ous means to boost a signal Unfortunately, doing so
typically also increases noise and interference in
ana-log systems Gain is descriptive of an antenna's
ca-pability to increase its effective radiated signal,
rela-tive to a reference like an isotropic antenna or a
cen-ter-fed, half-wave dipole antenna
galena A bluish-gray lead sulphide mineral
com-monly used as a sensitive radio wave detector in
crys-tal detectors in the early 1900s Sometimes the
ga-lena was thinly coated with other materials to improve
its properties
gallium arsenide GaAs A semiconductor substance
used to produce electronic components, such as
com-puter chips and solar panels (when combined with
germanium) It is sometimes used in place of silicon
for high speed devices It withstands heat and
radia-tion well, making it suitable for orbiting satellite
ap-plications
If used alone, the bandgap of GaAs is too high for
use as semiconductor lasers, so the material is
impreg-nated (doped) with other chemical elements and, as
such, is the main active material used to fabricate
semiconductor diode lasers, emitting pulsed light in
the infrared frequency spectrum
GaAs lasers can be used at room temperature and
cooler temperatures and, in general emit higher
wave-lengths at higher temperatures GaAs lasers emit a
wider, more diffused beam than gas lasers, but they
are small, inexpensive, versatile, and rugged and
suit-able for many applications See homojunction laser,
indium gallium arsenide nitride, semiconductor
la-ser
Galvani, Luigi (1737-1798) An Italian physicist,
educator and physician who experimented with
minute levels of electricity in the leg nerves offrogs
around 1786 Galvani 's wife had observed twitching
in a recently killed frog when a nerve was touched
and pointed it out to her husband; Galvani followed
up her observation with further experiments leading
to a better understanding of nerve impulse transport
in biological systems His name has been applied to
measuring instruments (galvanometer) and small
lev-els of electricity on skin surfaces (galvanic skin
re-sponse)
galvanic Related to or producing a direct electrical
current through chemical rather than electrostatic
means See galvanometer
galvanic cell A power cell that produces electricity through electrochemical rather than through electro-static means See battery
Luigi Galvani - Physicist
Luigi Galvani did numemus experiments innonbio-logical and bioinnonbio-logical electrical impulses The galva-nometer is named after him.
galvanometer Named after Luigi Galvani, an instru-ment for detecting low levels of electric current through the use of a magnetic needle or coil sus-pended within a magnetic field The basic concept of
a galvanometer is that very low levels of current, when channeled through a magnetic coil, can influ-ence the magnetic field sufficiently to deflect the coil (or needle) in one direction or the other, depending upon the polarity of the current The magnitude of the deflection (torque) is proportional to the amount ofcurrent Thus, the torque can be read and measured when compared against a calibrated scale associated with the receiver, indicating the direction and strength
of any current that may be present
The historic development of the galvanometer fol-lowed from principles described by 0rstedt and Ampere and was furthered by Johann Schweigger, who presented a paper on the galvanometer multiplier
in July 1820 Half a decade later, Ampere developed
a working galvanometer, as did Nobili, who used two needles, each with its own separate coil, to reduce in-terference from the Earth's magnetic field Nobili's innovation made it possible to position the device without worrying about the direction of the Earth's
magnetic meridian, thus creating a static
galvanom-eter It also made it possible to use a longer needle, thus increasing the size of the gauge and the ease of getting an accurate reading Nobili galvanometers designed by Ruhrnkorff were popular in the latter 1800s Most of the early galvanometers, known as tangent galvanometers, were constructed with a com-pass integrated into a surrounding electromagnetic coil
In 1858, William Thomson (Lord Kelvin) refined the
technology and created the astatic galvanometer, the
basis of more modern galvanometers In 1880, D' Arsonval further improved upon the technology,
by integrating a small coil with the metering needle, both housed within the field of a permanent magnet
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Thomson's mirror galvanometer, for example, was
used for reading currents on long submarine
commu-nications cables Following World War II, a dynamo
transformer, a type of torque motor, based upon the
moving-iron galvanometer, was patented by Mueller,
an American inventor
The versatile galvanometer is now also used in
aero-nautics, train, and power plant applications
A number of scientific instrument museums include
historic galvanometers in their collections, including
the Robert A Paselk Scientific Instrument Museum
in Arcata, CA Traditional galvanometers have been
partly replaced by solid state current meters for
in-dustrial current-measuring use; however, mechanical
galvanometers are still commonly used in schools to
help teach the principles ofelectromagnetism
Com-mercial galvanometers vary in size and shape but
most are about the size of a travel alarm clock and
have a semicircular or vertical scale (similar to postal
meters) for reading the measurements in amps, volts,
or other relevant units Electronic optical scanning
galvanometers are becoming important in the
scan-ning and printing industries See galvanic; Galvani,
Luigi; Schweigger, Johann
Historic Galvanic Power Cell
A historic electrochemical power galvanic cell
named after Italian physicist Luigi Galvani.
galvanometer, ballistic Atype ofgalvanometer
pat-ented by the Leeds &Northrup Co in the early 1900s
intended to measure the total charge (as opposed to
peak charge) or of a burst or short duration pulse of
current When the duration of the impulse to the coil
is short, the coil gives a short twist proportional to
the magnitude and duration of the current Ballistic
galvanometers are designed with a higher inertia coil
Some of the practical applications of ballistic
galva-nometers include the testing ofvarious configurations
in a prototype circuit board (e.g., combinations of
capacitors) and the experimental determination of
hysteresis curves for various substances or devices
See galvanometer
based galvanometer, consisting of a narrow, rectan-gular coil, suspended so that it can move between the poles of a permanent magnet to register a reading of direct current This version of the galvanometer, de-veloped by D'Arsonval in 1880, made the historic compass-based galvanometers obsolete They were designed with compact, more reliable casings than the tangent galvanometers, since an external circu-lar coil around the instrument was not used Later adaptations of thermocouples or rectifiers to the D'Arsonval galvanometer permitted the conversion
of alternating current (AC) to direct current (DC) in order to measure alternating current See galvanom-eter
galvanometer, mirror A device for measuring very low levels of current developed by Poggendorff in the 1820s and later refined by William Thomson (Lord Kelvin) in the 1850s that was a departure from the early compass needle style galvanometers The
mirror or reflecting galvanometer was used for
mea-suring current in submarine communications cables
in the late 1870s There were two main systems in a mirror galvanometer, the galvanometer with a mir-ror that reflected a beam oflight whose direction and extent was influenced by the polarity ofa tiny amount ofcurrent, and a lamp at the receiving end with a cali-brated scale that registered the light reflected from the galvanometer, shifting to the right or to the left depending upon the direction ofpolarity and amount ofcurrent See galvanometer
galvanometer, resonant A newer form of patented galvanometer technology that is being used in the printing industry for scanning images onto printing plates This somewhat revolutionary technology uses computer electronics to control a raster-based laser scanner without the use ofmotors or rotating mirrors Instead, the scanning mirror is associated with a tor-sion bar that is influenced by electromagnetic coils Thus, in practical use very high scanning speeds are possible and there are no significant mechanical parts
to wear out See galvanometer
gamma ferric oxide Ferric oxide is found as dark synthetic pigments and as natural red or black hema-tite Gamma ferric oxide has been used since the 1940s to provide configurable magnetic recording surfaces, first on magnetic tapes, later on floppy dis-kettes
gamma camera A device for detecting and record-ing gamma ray emissions The basic components in-clude a collimator, for preprocessing the gamma ray emissions entering at desired angles through gamma ray absorbing materials, a detector crystal (gamma ray scintillator), an array ofphotomultiplier tubes for converting the photonic energy into electrical energy while amplifying the electron emissions, output and logic circuits, and a processing unit (computer) for interpreting the data into meaningful information Gamma cameras are used in radiopharmaceutical imaging for detecting radiation that has passed through bodily organs to reveal internal structures and anomalies
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gamma testingThe testing of a product by
out-of-house testers who fit the profile of endusers who
would actually purchase or use the product being
tested It is the step before User Acceptance Testing
(UAT) or delta testing and after beta testing (in-house
testing) Gamma testers understand that the product
is essentially finished but there may still be a few
op-portunities for user input into the final design (an
important aspect ofsoftware design) The testers also
understand that the product is considered to be
bug-and defect-free but that a bug-free state is not 100%
assured because people outside the company haven't
used the product in a real life environment See beta
testing, User Acceptance Testing
gamut I.A range or series 2 In imagery, the color
gamut is the range of colors that can be perceived or
reproduced, usually within the context of a
particu-lar situation or technology For example, the gamut
of an RGB cathode-ray tube (CRT) monitor is quite
different from the gamut of printing inks or process
color perceptual combinations of dots The gamut
range of videotaped images is narrower than that of
film-based images It is important to understand the
differences in order to adapt the technologies to one
another See dynamic range 3 The range of
wave-lengths within a spectrum that are usable, viewable,
or of scientific interest
GANSee global area network
GandalfFZACompression ProtocolOne of
sev-eral mechanisms proposed in the mid-1990s to
en-able compression of PPP encapsulated packets
Gandalf is based on FZA, which was developed by
David Carr at Gandalf Data Ltd and enhanced as
FZA+by Abbie Barbir It is a derivative of LZ that
optimizes at the expense ofCPU cycles and memory
in order to achieve high performance compression,
available on a fee or royalty basis See Compression
Control Protocol, Deflate Protocol, Point-to-Point
Protocol, RFC 1993
gangTo group or aggregate cables, components,
ob-jects, or picture elements To mechanically or
elec-trically combine components or devices so they can
be controlled from one source
Gang of NineNine vendor companies who formed
a group in 1989 to promote and develop the industry
standard architecture (ISA) which is commonly used
for computer peripheral device connections on
Intel-based microcomputers Their work resulted in the
32-bit Extended ISA (EISA) standard
gapOpening, space, small distance between objects
or signals, small distance ofa less dense material than
the surrounding materials
GAPSee Generic Access Profile
gap, electricalAnopening in an electrical
connec-tion, which may close to allow a circuit connection
or, more commonly, over which a spark will jump to
provide a brief connection or discharge through the
air, as the gap in a spark plug on an engine.An
un-planned gap, through breakage, can interrupt an
op-tical or electrical connection, thus interfering with a
transmission
gap, pickupThe distance between a reading/recording
head and the medium with which it interacts The dis-tance is often very precise, as in hard drive read/write heads and compact disc pickups, where a slight ad-justment allows a much greater density of recorded pits in the disc
gap, timeAninformational space or time gap inserted
to indicate a stopping and/or starting point in recorded material or in a coded transmission
gap lossThe loss in signal strength that occurs when crossing a gap Even very tiny gaps may substantially affect the quality of a transmission, and gaps are apt
to occur at comers and junctions where transmission media change and in couplers
garbage1 In computing, meaningless information, spurious characters, nonsensical output 2 A mean-ingless signal or electrical interference See interfer-ence, noise
garbage in/garbage outGIGO.colloq Ameans of
saying that you can't get something good out if you have put something bad into a system In computer terms, it means that if you supply bad input, you're not going to get good output In terms ofhardware, a weak or poor signal at the origin is not going to re-sult in a good signal at the receiving end In program-ming terms, feeding the computer the wrong instruc-tions or the wrong data is not going to result in the software performingina correct or desired manner
In management terms, providing bad instructions and motivations to subordinates is not going to result in good work even if they are capable professionals garbleA communication or signal in which some portion of the content has been changed to be unde-cipherable, unintelligible, out of sequence, or other-wise undesirably "scrambled." The change is usually
in terms of the strength or content of the signal
A phone conversation may sound garbled ifthe speed
of transmission is inconsistent with the speed of the spoken message, resulting in words running together
or pauses that are inappropriate It may also sound garbled if there are power fluctuations causing the sound level to significantly fade in and out or ifthere are other signals overlaying the desired signal, mak-ing it unintelligible (e.g., party line noise, crosstalk) Thus, in voice and radio communications, the term tends to be associated with reduced intelligibility re-lated to informational timing problems, power fluc-tuations, or multiple signals overlaying portions of one another
In data communications, the term tends to be associ-ated with portions of a communication arriving out
of sequence or interspersed withnonsensical or scrambled data It can also occur in encrypted mes-sages if the decryption algorithms do not work cor-rectly A file or data communication may be garbled ifpackets are reassembled in the wrong order or have inappropriate portions merged into existing packets
or between the appropriate packets.Asin voice com-munications, garbled data can result from power fluc-tuations but it can also arise from programming bugs
or programming deficiencies, such as insufficient or inappropriate error checking Surge suppressors, power conditioners, robust and appropriate (for the
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mitigating problems associated with garbled
Garden Valley Telephone CompanyGVTel The
oldest telephone cooperative in the United States,
chartered in Minnesota in 1912 and still operating
after more than 88 years
Garfield, OliverAnauthor and engineer, in 1955
Garfield wrote a 63-page book Simple Electronic
Brains and How to Make Them as a practical
embodi-ment and compleembodi-ment to Edmund C Berkeley's 1949
book Giant Brains or Machines that Think The two
men partnered for a while to produce computing
mechanisms such as the Geniac, in the mid-1950s
Unfortunately, there were disputes and a lawsuit;
Garfield and Berkeley ended up selling the
comput-ing devices as the Brainiac and Garfield got the name
Geniac The original Geniac (later the Brainiac) was
an innovative computing device that could be
con-figured to play simple games
While the author of this text couldn't find hard
evi-dence of wrongdoing, Garfield's business practices
may not have been entirely legal For a while
Gar-field used the Geniac name to promote his GENIAC
Pocket Calculator.Itwas a repackaged Otis King
cal-culator (a cylindrical slide rule) sold after the breakup
with Berkeley through the Oliver Garfield Co., Inc
The Otis King calculators were serial numbered and
shipped from England Some of the Garfield
calcu-lators have all the original Otis King markings
re-moved or, more likely, Garfield stole the design and
cloned it without the identifying marks It is unlikely
he had permission from Otis King to distribute their
calculators without attribution, so perhaps this sheds
some insight as to why his dealings with Berkeley
didn't work out See Berkeley, Edmund; Geniac
garnetA red, more or less transparent semiprecious
mineral often used in jewelry and industrial
applica-tions.Itsomewhat resembles ruby but is generally a
little less transparent and a deeper, muddier shade of
red Synthetic garnets can be manufactured from
ox-ides ofsome ofthe rare earths Lasers and some types
ofcomputer memory that use magnetic film are made
from garnet See gadolinium, laser
GARP See Global Atmospheric Research Program
gas laserA laser in which a gas or vapor is used as
the active medium The gas may be excited by a
high-frequency oscillator or direct current Ion lasers use
noble gases such as argon Apulse of voltage is used
to ionize the gas and direct current (DC) can be used
to maintain the state of ionization Gas lasers were
pioneered by A Javan in 1960 and the argon laser
was developed in the mid-1960s by William Bridges
See laser, laser history
gas maserAmaser in which a gas or vapor interacts
with microwaves Gas masers are found in scientific
oscillators such as atomic clocks See atomic clock;
Dicke, Robert; laser history; maser
gas plasma displaySee plasma display panel
gas tubeAtype ofelectron tube that is not completely
evacuated Early electron tubes burned out quickly
because of the gas inside the bulb Later tubes were
cialized applications, a trade-off is used and a small amount of gas is left in the tube to promote ioniza-tion to enhance current flow
Gassner, Carl, Jr.AGerman-born inventor who first created a commercially practical dry cell, based on a sealed zinc container that, for the most part, super-seded the wet cell In November 1887, Gassner was granted U.S Utility Patent #373,064 for his inven-tion Dry cells were welcomed because they didn't have the problems of leakage associated with wet cells, and they could be made smaller and more por-table They were an important innovation and are still
in use today in the fonn ofcarbon-zinc batteries See dry cell; Leclanche, Georges; Plante, Gaston gastonA random noise modulator sometimes used
as an antijamming communications transmitting de-vice
gastroscopeDeveloped around the 1930s as one of the historic fiber optic medical imaging technologies, the gastroscope makes it possible to peer inside the gastric (digestive) system It is especially useful for locating and illuminating structures such as suspected tumors in the stomach
GATSee Generic Addressing and Transport Protocol gateIn an electrical circuit, in its broadest sense, a junction that selectively controls whether current gets through, when it gets through, or how much ofit gets through
gate, securityIn a software program, an input or pro-cess point that selectively lets users or other propro-cesses through, as a security gate, login gate, or system gate-way for different types of information or protocols (network traffic, mail, etc.) In the more specific con-text of programming, a circuit that performs a basic logic operation and provides a single output from that operation See firewall, gateway, proxy
gate, telephoneIn telephone call distribution sys-tems, a physical or virtualtrunkthrough which calls are handled by a group ofoperators or agents accord-ing to some characteristics specified for each gate Gates, William Henry, HI(1955- ) Bill Gates is a prominent success story in the personal computer in-dustry and has a major influence on the direction and type ofsoftware that is available to consumers around the world today In the 1980s he went from entrepre-neur to software magnate, earning billions ofdollars
by investing in technology and selling computer op-erating systems and basic business software tools Gates began programming seriously in Seattle, Wash-ington, while still in grade school, along with his friend and business partner, Paul Allen, who was two years older Gates came from a privileged family with many solid business contacts, and Allen and Gates were both precocious entrepreneurs, successfully winning commercial programming contracts at a young age Their first business partnership, based upon traffic analysis software, was called Traf-O-Data, founded around 1972
The economic success of Microsoft began with the signing of the IBM OSIBASIC contract Ofparticu-lar importance is the fact that Gates reserved the right
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to market the results ofthe development (sold by mM
as PC-DOS)incompetition with IBM, a contractual
loophole that Gates had also achieved with MITS,
who were dismayed because they thought they had
bought the exclusive rights to Microsoft BASIC for
the Altair Gates' father was a lawyer and Gates had
a long-standing interest in contracts and business
deals, which probably accounts for the
Microsoft-fa-vorable outcome of the two pivotal contracts Times
have changed; today large corporations have teams
of lawyers to develop and scrutinize contracts but,
two decades ago, many deals were still established
on trust and a handshake or on less extensive
paper-work and scrutiny than is common now
Since Gates and Allen didn't have an operating
sys-tem to sell to ffiM, they bought QDOS, developed
by Tim Paterson In one of computer history's
great-est ironies, Tim Paterson acknowledged that he had
created QDOS by using a mid-1970s version of the
documentation for Gary Kildall's CP/M Microsoft
then hired Paterson to quickly develop it into
PC-DOS QDOS was syntactically and functionally
simi-lar to Kildall's CP/M Microsoft's version of a PC
operating system, sold in competition with the
prod-uct they produced for ffiM, became known as
MS-DOS In addition to operating systems, Microsoft
began developing business tools, word processors,
spreadsheets, etc., and buying up competitive
prod-ucts and companies including FoxPro, Stacker,
Altamira Composer, Vxtreme, Vermeer (now known
as Frontpage), Web Mapper, Softimage, Web~and
others Microsoft also now has stakes in several
broadcast and cable companies
In1982, Kildall's Digital Research Inc sued
Micro-soft Corporation and ffiM for copyright infringement
ofthe CP/M operating system Digital Research won,
but by this time Microsoft's momentum was so great,
few people heard about the suit and Kildall's
com-pany lost its majority market share The situation was
still ofconsequence almost twenty years after QDOS
was purchased, however, as Caldera, the new
own-ers ofKildall's early and later operating systems
tech-nology, pursued legal avenues against Microsoft In
July 1996, Caldera, Inc filed suit against Microsoft
Corporation for damages and injunctive reliefunder
U.S antitrust laws for "illegal conduct calculated to
prevent and destroy competition in the software
in-dustry."
Allen left Microsoft in 1983 for health reasons and
to pursue other investments through his own
com-pany, buthemaintained close personal ties with Bill
Gates He served on the Board ofDirectors
ofMicro-soft for a time, announcing his intention to resign and
become a strategy advisor as ofNovember 2000 In
the late 1990s, Gates was still head of the
organiza-tion that had grown from a small group ofhalfa dozen
programmers and clerical staff to a campus in
Red-mond with tens of thousands of employees and
as-sets in the billions The controversy did not die down,
however.In May 1998, the United States ofAmerica
filed a complaint against Microsoft Thus, Gates'
ac-tions as CEO came under severe scrutiny, a position
he resigned in January 2000 He continued to hold the position of Chairman, however
Gates has spun off a number of other businesses, in-cluding a multimedia company and the Teledesic In-ternet in the Sky project that he is co-developingwith Steve McCaw He is clearly interested in expanding into the broadcast and telecommunications fields and heavily promotes the use ofMicrosoft's Web browser Gates is one of the richest people in the world, and one of the most focused, aggressive, and successful business and marketing giants in the software indus-try Allegations of antitrust violations are part of an ongoing investigation of Microsoft by the U.S Jus-tice Department on behalf of hundreds of software developers who don't feel they can compete against
a company allegedly succeeding because of unfair business practices Whatever the results ofthe inves-tigation, part of Bill Gates' success is due to his am-bition, tenacity, and all-encompassing competitive drive Nonetheless, there is much controversy over his ethics, methods, and acquisition ofproducts from other sources that he has marketed as his own gatewayA transmission connection between net-works that handles information flow and typically performs bandwidth and protocol adjustments and conversions, as needed It may also combine (aggre-gate) network transmissions from several devices connected to a smaller number of network connec-tions Gateways are commonly used between dissimi-lar networks such as between local area networks (LANs) and the Internet (proxy servers), and between land services and satellite services, etc When local nets are connected with external nets, the gateway may also perform security functions Gateways are used on both wired and wireless networks Wireless gateway networks use radio transceivers rather than physical connections for wire or fiber optic cables Wireless networks also tend to have additional secu-rity features and encryption schemes to compensate for the fact that it's sometimes difficult to determine
if someone is intercepting wireless transmissions Consumer-oriented gateways that are available as peripheral devices may include Web server software and other utilities to facilitate Internet connections and firewall, logging, or other security schemes to protect data transmissions or specific devices from unauthorized access
A gateway differs from a proxy in that a gateway handles requests as though the requests originated from the gateway and not from the original client, thus serving as a server-side portal in a firewall See fire-wall, proxy
Gateway to Gateway ProtocolGGP Ahistoric, ex-perimental TCPlIP network transport layer routing protocol used to convey routing information through
a distributed shortest path computation The proto-col was primarily used for gateway-related tasks such
as routing datagrams.Itis now considered obsolete and developers are cautioned not to implement it See RFC 1009, RFC 1812
gating 1 Selectively allowing certain waveforms, frequencies, or portions of waves to pass through a
Trang 6plication of a certain current or waveform 3 Using
logic to control the passage ofcurrent or information
through a system
gaugeAn instrument or other indicator for
measur-ing or testmeasur-ing.Anindicator of the thickness or
thin-ness of a substance or object, especially applied to
wires and cabling Position relative to another, as in
the distance between the sides ofa railroad track See
American Wire Gauge (Brown and Sharpe),
Birmington Wire Gauge, Steel Wire Gauge
gaussAcentimeter-gram-second (CGS) unit
ofnetic flux density For example, if one line of
mag-netic force passes through one square centimeter, the
field intensity is said to be one gauss Named after
Karl Friedrich Gauss See lines of force, magnetic
field
Gauss - Mathematician&Astronomer
A portraitfrom a German postage stamp
commemo-rates the achievements of Carl (Karl) Gauss who
mathematically described important basic concepts
in magnetism, surveying, and mathematics.
Gauss, Jobann Karl Friedrich(1777-1855)
Abril-liant German mathematician and astronomer who
devised the heliotrope, an instrument that could
re-flect sunlight over long distances, providing a means
for making straight lines and calculations related to
the Earth's swface He investigated terrestrial
mag-netism in cooperation with W Weber in 1831 and
published some significant papers several years later
In 1833, he constructed an electric telegraph, just as
similar devices began to be developed in the United
States The gauss unit for magnetic flux density is
named after him
Gauss's lawAs it applies to dielectrics (without
get-ting into integrals), the total electric flux of a closed
surface (a surface without holes) equals the charge
enclosed divided by the permittivity Gauss's law
fa-cilitates the assessment of a stationary enclosed
charge associated with a surface by mapping the
sur-face field outside the charge distribution See
Ampere's law, Coulomb's law, dielectric, flux,
Gaussian surface, Maxwell's equations
often called abell curve due to its shape, and a
nor-mal curve due to its experimentally observed or theo-retical distribution (depending upon context) The concept and observations on larger statistical sets to confirm the concept were developed over a couple
of centuries, with A de Moivre noting in the 1730s that the binomial distributions described earlier by1
Bernoulli took on the characteristics of a continuous curve when developed using increasingly large sample populations Around the late 1700s,1.Karl Gauss enlarged on the concept, finding many appli-cations for its use He thus popularized the bell curve
~£~E~i~~~ia~:~~U::d~~o:~~e~i~=~~ ill representation that resembles the outline ofthe curve
ofa bell Its structure is based upon a combination of observed population distribution (in the statistical, not the human sense) and assumptions about its generalizability In a diagrammatic representation of the curve, the majority of occurrences of a phenom-enon fall within the center and highest point of the curve (the mean and mode) The changesin the di-rection ofthe curve and dispersion offrequencies are symmetric to either side of the mean and mode and are described in terms ofstandard deviations.
Aninteresting demonstration of the shape and dis-tribution ofelements in a Gaussian curve can be seen
in a number ofscience museums It is set up with ver-tical channels and ping pong balls (or ball bearings),
in which the balls are dropped into the top of a de-vice where they randomly roll down into a line of channels that can be viewed through a transparent panel After many hundreds ofballs have fallen down through the mechanism, the shape of the curve will emerge, with the majority of balls in the center, and fewer as you move left or right out to the edges (the tails of the distribution) due to the lower statistical probability of the balls moving farther and farther from the main center of the path
Gaussian curve models are at the heart of many ex-periments and statistical theories Relationships such
as that between optical intensity and frequency will often fit Gaussian models, though they may be skewed in one direction or the other due to environ-mental effects
Conformance to a normal "bell" curve is frequently
an underlying assumption for the design and scoring oftests Unfortunately, it is sometimes used as ajus-tification for describing populations where the size ofthe sample being evaluated is not mathematically sufficient to justify assumptions about its relationship
to the normal curve
Gaussian minimum shift keyingGMSK Atype of wave modulation from the frequency shift keying family used in wireless communications such as cel-lular phone systems and, notably, the Global System for Mobile Communication (GSM) GMSK is a com-promise solution, as it is less efficient than some types ofmodulation, but it is popular for its cost benefit In GMSK, a digital signal is modulated onto the analog
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carrier frequency as the phase of the carrier is varied
by the signal information AGaussian filter is applied
before modulation Most ofthe power is concentrated
at 250 kHz and there is low incidence of channel
in-terference Commercial applications of GMSK for
mobile telephony were described in the early 1980s
and later put into practical use in GSM In 1996,
Thierry Turlette authored a frequently cited paper on
GMSK "GMSK in anutshell." In the late 1990s, more
efficient algorithms for GMSK were suggested by
re-searchers See phase shift keying
Gaussian noiseNoise or other electromagnetic
in-terference that conforms to a probability pattern
con-sistent with expectations based on Gaussian statistics
Noise that is somewhat random across a range
offre-quencies is sometimes known as white noise or
Gaussian noise
Gaussian surfaceA theoretical surface providing a
geometry analogous to a physical surface to
facili-tate modeling and calculations related to electric
fields See Gauss's law
Gauthey, DomA French monk who invented a tube
system for channeling acoustics, in essence a
"speak-ing tube" or historic manual telephone conduit
(ap-parently derived from ship-based speaking tubes) It
consisted basically of a tube with funnel shapes on
the ends for speaking and listening The interesting
aspect of the idea is that it was suggested the tubes
could be organized in relay, with human speakers
(re-lay agents) at the junction of each length of tube
Thus, it would be theoretically possible to
commu-nicate a message more than 500 kilometers in less
than an hour He presented his invention to the
l'Academie des sciences (Academy of Sciences) ca
1782, transmitting sound over a distance of 760
meters See telephone history
Gb, Gbytegigabyte See giga-
GBgigabit See giga-
GBCSSee Global Business Communications
Sys-tems
GBICGigabit Interface Converter A small,
some-times swappable, fast gigabit network converter
de-vice that attaches to a port connection
GBRground-based radar See radar
GCA1 See game control adapter 2
ground-con-trolled approach Aradar-based aircraft landing
sys-tem
GCIGround Control of Interception.Aradar-based
technique for directing aircraft in the interception of
approaching craft
GCMDSee Global Change Master Directory
GCRASee generic cell rate algorithm
GCS 1 Government Communication Systems
2 Great Canadian Scientists.Aproject to increase
awareness of great scientists with Canadian
affilia-tions and roots originating from a lack ofprint
mate-rials on the subject Many of the profiled scientists
have contributed to the telecommunications industry
GCTSee Greenwich Civil Time
GDFgroup distribution frame See distribution
frame
GDGSee Global Development Gateway
GDISee graphics device interface
Geissler tube Atype of sealed dual-electrode gas-filled tube that glows when current passes through
it The color ofthe glow varies with the types ofgases used, and the wave characteristics can be influenced
by the amount and type of current applied Historic versions ofthe Geissler tube, named after the inven-tor J Heinrich Geissler, resembled glass lanterns or candles mounted on a metal or wood base with a straight or spiral illumination up through the center
of a second, protective glass bulb (sometimes filled with a colored liquid to enhance the effect ofthe pri-mary illumination in the inner tube) Some of the smallest, earliest tubes lacked a stand and protective bulb but came in a variety of creative and charming shapes resembling short strings ofhollow glass beads Early Geissler-style tubes were used for signs and lamps, more recent variations are used as scientific research and calibration instruments Over the de-cades, Geissler tubes have played a role in many pio-neer aspects of electronics and telecommunications leading to the development of the light bulb, flash bulbs, a number of projection technologies, and the discovery of cathode rays
In contemporary calibration tubes, the central region ofthe tube is usually narrower than the ends The very narrow region in the center induces strong spectral lines for sample comparisons The Geissler tube is useful for calibrating optical instruments and as a ref-erence tool.Ithas also been used in conjunction with imaging technologies as a low-cost experimental ro-tating mirror photodetection device
Educational versions of the Geissler tube often have more than one tube, each with different contents These are useful for teaching about gases, induction, fluorescence, and other related concepts For ex-ample, an energized Geissler-style tube can be used
to illustrate magnetic field influences on charged par-ticles Geissler tube effects may be observed by the unaided eye or with scientific instruments such as spectroscopes See cathode-ray tube, Crookes tube Geissler, Johann Heinrich Wilhelm(1814-1879)
AGerman physicist and glassblower who established
a workshop in Bonn, where he crafted scientific ap-paratus One of his more significant inventions was
a type of mercury air pump that is still in use today for evacuating the air from bulbs and various labora-tory apparatus In collaboration with Julius Pliickers, Geissler did experiments to measure the density of water He also created instruments for the measure-ment of vapor Modem refinemeasure-ments of the Geissler tube, that he developed in the late 1850s, are still used for scientific calibration See Geissler tube
GEMSee Graphics Environment Manager GEMINAXGlobal Enhanced Multiport integrated ADSL Transceiver.Anintegrated voice and data chipset provided by Infineon Technologies, GEMINAX was selected for the North American Litespan next generaltion network digital loop car-rier multiservice broadband access platform The chipset can be integrated into cost effective, very high density linecards for voice and DSL-based data
Trang 8GEMSSee Global Environmental Monitoring
Sys-tem
genderA designation widely used to cable
connec-tors to indicate whether they are female "innies," or
male "outies," that is, whether they have holes or
ex-tended pins If it is a simple round or squarish
con-nector like a switchboard or composite video
connec-tor, the female end is usually called a plug while the
male end is usually called a jack
Most common switchboxes for computer data
con-nections have female connectors Male and female
connectors are both found on the backs of
comput-ers, and vary from platform to platform and
some-times even from brand to brand This variation is
in-convenient for users, who often have to pay extra
money for gender changers, but cabIe and connector
manufacturers don't seem to mind the extra business
Gender Bending Adapters
Gender benders are commonly used to make
con-nections between cables with the same male orfemale
contacts facing one another Some common gender
benders used with serial cables include (A) DB-25
regular; (B) DB-25 slimline; (C) DB-9 regular The
slimline models are convenient for portable devices,
such as laptops, for connecting to modems orprinters.
gender bender/changer/converterA small
con-necter designed to change the gender ofa plug or
re-ceptacle in order to enable connection to another plug
or receptacle The male end is the one in which the
contact points protrude from the connecter The
fe-male end is the one in which the contacts are
de-pressed Thus, a simple gender bender has two female
ends or two male ends Switchboxes and adaptors
sometimes also perform gender bending functions
Adapters/extenders (male on one side, female on the
other) are sometimes erroneously called gender
bend-ers, because they superficially resemble them, but
have different genders Gender benders are usually
passive devices that do not influence the signal
pass-ing through the device See adapter, extender, switch
box
General Instrument CorporationGIC Abroadcast
technology corporation which is significant because
it was the first to suggest an all-digital broadcast
sys-tem to the Advisory Committee on Advanced
Tele-vision Service (ACATS) for consideration for
recom-mendations to the Federal Communications
Commis-sion (FCC) and the U.S Congress Subsequent to the
increased, and ACATS and other advisory bodies brought the thinking about television technologies into closer alignment with recent digital advance-ments
In a separate but related matter, General Instrument Corporation sought, through the U.S courts, to hold the FCC to the mandate to ensure "Competitive Avail-ability of Navigation Devices" (e.g., cable set-top boxes) to maintain the right ofcompetitors other than cable companies to produce and distribute these vir-tual navigation devices However, as of June 2000, the court decision was to reject GIC's challenge to
an FCC separation requirement for hybrid navigation devices See Advisory Committee on Advanced Tele-vision Service
General MagicACalifornia-based commercial ven-ture established in 1989 that focuses on providing innovative, cost-effective computer-Internet-tele-phony products for mobile applications Products in-clude Portico, a development name for integrated voice/data communications and information services, and DataRover integrated voice/data hardware de-vices
General Packet Radio ServiceGPRS A wireless high-speed data communications standard operating over Global System for Mobile Communications (GSM) networks GPRS is a packet-based air inter-face using existing circuit-switched GSM networks GPRS offers enhancements to basic GSM It provides functional connections with the Internet that were not possible with earlier systems.Itcan operate at speeds ranging from 9.6 Kbps to 115 Kbps (with plans for rates up to 384 Kbps) and offers live connections to mobile users such that users can be online continu-ously, without paying minute-by-minute fees other than when uploading or downloading information The higher data rates possible with GPRS not only reduce connect time costs but enable broader-band services, such as videoconferencing, to be imple-mented on mobile devices Full implementation of these higher data rates are somewhat dependent upon the evolution ofthe underlying GSM technologies but will likely be realized over the next two years or so Many see GPRS as a bridge between GSM and 3G mobile services
General Protection FaultGPF Acommon fault con-dition encountered by users of Microsoft Windows software when applications memory conflicts occur
At the very least, applications should be closed up Unfortunately, it may also be necessary to reboot the system
General Radiotelephone Operator LicenseGROL
A lifetime operator's license granted by the Federal Communications Commission (FCC) upon success-ful completion of competency requirements The li-cense is required for individuals who adjust, main-tain, or service FCC-licensed marine, aviation, and international radiotelephone transmitters It conveys the operating authority ofthe Marine Radiotelephone Operator License and requires the Written Element
1 and Written Element 3 exams to be passed
Trang 9Fiber Optics Illustrated Dictionary
Some related FCC radiotelephone authorizations
in-clude the First, Second, and Third Class
Radiotele-graph Operator Certificates These require exams, in
some cases Morse Code competency, and are valid
for five-year terms (renewable) A GROL-licensee
may also be granted a Ship Radar Endorsement on
qualifying and passing the Written Element 8
exami-nation This permits the repair, maintenance and
in-ternal adjustment of ship radar equipment There are
also licenses specific to the Global Maritime Distress
and Safety System See GMDSS Radio Operator
Li-cense
General Switch Management Protocol GSMP.An
IETF standards-track packet network administration
protocol to control a frame- or cell-based label switch
GSMP is an asymmetric protocol supporting master
(controller) and slave (switch) interactions GSMP
provides a means to query and report connection,
port, switch, and Quality of Service (QoS)
informa-tion and statistics for MPLS label switch devices from
or to a third party controller Thus, GSMP can be used
to query switches, to establish and release
connec-tions, to modify a multicast connection, and to
man-age switch ports It can also notify the controller of
asynchronous events Multiple instantiations of a
single controller can be used to control multiple
switches and partitioning is supported for the control
of a single switch by multiple controllers
The capability to query and report switch-related
con-figuration and statistical status is particularly
valu-able for remote switch operations and, as the
proto-col evolves, is desired for optical network
configu-rations as well Initially, GSMP was developed to
work with static switch partitions; however, dynamic
forwarding to multiple administrative domains might
be feasible for future versions of GSMP
GSMP does not make significant assumptions about
the underlying hardware over which it is transmitted
and thus can be implemented in a variety of types of
networks As a separate standards-track document,
packet encapsulations for GSMP transport have been
defined for ATM, Ethernet, and TCP networks:
InATMnetworking, GSMP packets are
vari-able length and encapsulated directly in ATM
AAL-5 with an LLC/SNAP header
• For Ethernet, GSMP packets are transmitted
after the Ethertype Ox880C identifier up to a
maximum length of 1492 bytes
In TeP/IP, GSMP is transmitted after a
prepended TLV header field of type Ox88-0C
and an integer indicating the length of the
fol-lowing GSMP message The message is
pro-cessed after its successful receipt TCP/IP
en-capsulation can also be transmitted with
au-thentication
With the evolution of GSMP towards an industry
standard in the late 1990s, there has been interest from
the commercial and developer communities in
defin-ing GSMP for other environments, includdefin-ing
experi-mental switches and patented, proprietary switches
Thus, GSMP for FSR switches (VTT Information
Technology) and ForeRunner (Sprint) switches are ofinterest to developers See flow, Ipsilon Flow Man-agement Protocol, RFC 1987, RFC 2026
Generalized Trunk Protocol GTP Atelephony pro-tocol enabling complex Channel Associated Signal-ing (CAS) and Common Channel SignalSignal-ing (CCS) protocols to be executed in peripheral devices in or-der to remove some of the processing load from the main processor
generator In its basic sense, a machine that is de-signed to convert mechanical energy into electrical energy, or one that converts direct current (DC) into alternating current (AC) Dynamo
Generic Access Profile GAP Aprofile is defined by the Open Systems Interconnection (OSI) model as a combination of one or more base standards and as-sociation classes, necessary for performing a particu-lar function The GAP specifies well-defined com-patibility levels for DECT products, as an extension
of an ETSI-published Public Access Profile (PAP) incorporated into Digital European Cordless Tele-communications (DECT) See Digital European Cordless Telecommunications
Generic Addressing and Transport Protocol GAT
A digital telephony protocol for exchanging Appli-cation Protocol data units (APDUs) between service provision points It may be used between a terminal and a network or within or among networks The rec-ommendations for GAT use with ISDNIB-ISDN is described in ITU-T Q.860
generic cell rate algorithm GCRA In ATM net-working, an algorithm used to enforce a particular performance level with regard to cell traffic The GCRA evaluates the cell to determine whether it con-forms to the established cell traffic contract In a net-work switch, the UPC function will typically incor-pot'ate an algorithm such as GCRA to enforce con-formance with the specified parameters See leaky bucket for a fuller explanation and example See cell rate for related concepts
generic flow control GFC In ATM networks, a means of controlling traffic flow A field in the ATM header can be used to designate flow control param-eters This field is evaluated en route, as appropriate, and is not included in the final delivered communi-cation See cell rate
generic flow control field GFC In ATM network-ing, traffic flow control is an essential aspect ofmov-ing cells from one place to another In the ATM header, there are priority bits which can be set to in-form the end-station that congestion control may be implemented by the switcher See cell rate
Generic Security Service Application GSSA.An IETF elective proposed general Internet standard See RFC 2078
GENIAC Genius Almost-Automatic Computer (in the tradition of the UNIVAC, ENIAC naming con-vention) The GENIAC was a personal computing device designed by Edmund C Berkeley and possi-bly also Oliver Garfield in the mid-l 950s Berkeley was an insightful author, robotics entrepreneur, and the designer of what was likely the first desktop
Trang 10author, engineer, and business person in much the
same vein as Berkeley Unfortunately, the partnership
ended up in disputes and Garfield ended up with the
name Geniac while Berkeley continued marketing
computing devices under the name Brainiac
The GENIAC kit was originally sold through
Ber-keley Enterprises, Inc., documented by Oliver
Garfield's GENIACS: Simple Electric Brain
Ma-chines, and How to Make Them bound with the
Manual for Geniac Electric Brain Construction kit
No.1.Once assembled,itcould play simple games
and do basic computations The kit sold for about
$15.95 to $19.95 (about two days' wages) Logical
functions were carried out electromechanically,
through cascading rotary switches that could be
con-figured for different computing experiments For
in-formation on the GENIAC Calculator, see Garfield,
Oliver See Berkeley, Edmund C.; Brainiac; Simon
geographic information systemGIS Any system
in which terrain infonnation is gathered, processed,
and stored, usually for later retrieval for analysis,
long-term comparisons, mapping, navigation, etc An
enormous amount ofgeographic infonnation is
gath-ered by orbiting satellites, geocoded, and stored on
high storage-capacity computer systems, much of
which is accessible through public computer
net-works Land-based tracking ofnetworks, utilities, and
transportations systems is also carried out with GIS
systems See geoInterface, Landsat
geographic interfaceThis term has two meanings:
(1) interfaces designed for users to access and
ma-nipulate geographic data, and (2) an evolutionary step
in computer user interfaces which models the world
inasimulated3D environment as visual objects or
func-tional constructs
The second meaning represents a relatively new
ap-proach to computer user interfaces The idea has been
around for a while, but the resources to implement it
have been cost prohibitive until recently In the early
1970s, microcomputer user interfaces consisted of
dipswitches for input and small blinking lights for
output (see Kenbak-l and Altair) They were replaced
by simple monochrome, text-based interfaces by
1975 (see SPHERE System) In the early 1980s,
de-velopers began producing graphical user interfaces
(based largely on 1970s research at Xerox PARC),
and it was not long after that the first experimental
geographic interfaces began to appear See
geoInterface, graphical user interface,
object-ori-ented, Open Systems Interconnection
geographic northThe region on the Earth called the
North Pole from which imaginary lines of longitude
emanate to meet again on the other side at geographic
south, as established by convention Geographic north
is the general direction in which the north-seeking
needle on a compass points but it is not exactly the
same as magnetic north, which changes as large
geo-logical formations change See magnetic north
Georgia Rural Telephone MuseumLocated in a
former 18,000-ft cotton warehouse, built in 1911, the
Georgia Rural Telephone Museum opened officially
lished across the street from the Citizen's Telephone Company It includes about 2,000 historic telephones and other examples of communications equipment
http://www.sowega.net/ museum!
Geostationary Meteorological SatelliteGMS A geostationary satellite system ofthe Japan Meteoro-logical Association(JMA)and the National Space Development Agency (NASDA) that is affiliated with World Weather Watch(WWW). The GMS system senses the region over Asia and the western Pacific
at 140 degrees E longitude It is similar to the U.S
GOES system The first GMS was launched from the
~:~~~~;£:~~~::&~~~:~~~~~i~~~e~r~~ i~~~ ill GMS-5, which has been operational since the
mid-1990s, provides data on cloud patterns (including volcanic activity), water vapor distribution, and sea surface patterns to more than two dozen countries
The Japan WeatherAssociation provides hourly GMS images online GMS systems also serve as commu-nications relays for forwarding information obtained from ships, aircraft, and communications buoys and provide assistance in emergency search and rescue operations By the late 1990s, the GMS system was being designed to take on a broader role, serving not only as a meteorological sensing system and relay station, but also as an air traffic control support system
In February 2000, the GMS-4 system, launched in
1989, was taken out of service and moved out of the way into a higher region for its final orbit The
GMS-5 system, launched in 199GMS-5, is still operational and apparently in good working order, but a transition is being made to a new system of satellites, the Multi-functional Transport Satellite (MTSAT) series, begin-ning with MTSAT-IR and MTSAT-2 Despite its age, GMS-5 is expected to be able to operate until the MTSAT platfonns come online around 2003 See Multifunctional Transport Satellite, National Space Development Agency
Geostationary Operational Meteorological Satel-liteGOMS Also known as Elektro, the GOMS sys-tem is a tbree-axis-stabilized imaging satellite that is part of the Russian Federation Planeta-C Meteoro-logical Space System The first ofthe series of satel-lites was launched in October 1994, with each plat-form expected to last at least three years GOMS or-bits over the Earth's equator at longitude 76°50' E
GOMS senses infrared images ofthe Earth's surface and cloud cover, provides continuous coverage of atmospheric patterns, detects potentially hazardous phenomena, measures seasurfacetemperattrres, and monitors space-borne energy particles
Aboard the satellite, a radiometric line scanner im-ages the Earth, digitally encodes the information, and transmits it to a ground station for preprocessing and eventual dissemination as satellite products The com-munications portion of GOMS includes satellite-to-ground transmissions, satellite-to-ground-station intercommu-nication relays, and transmission to users on an operational basis