Fiber Optics Illustrated Dictionary - Part 46 ppsx

Hollerith cards were used to store historic comput-ing machine code in the days before tape, diskette, and hard drive storage.. Punch cards, in general, can be fully cal devices, or part

Fiber Optics Illustrated Dictionary

BEeSee Header Error Control

hecto-(symb - h)ASysteme Internationale (SI) unit

prefix for 100 or 102

• Heisenberg uncertainty principleProposed by W

Heisenberg in 1927, the uncertainty principle has

since become a fundamental principle of physics

(Heisenberg formulated a model of the structure of

an atom in the 1930s which has held up well over

time.)Instudying movement ofelectronics,

Heisen-berg proposed mathematically that it is not possible

to determine precisely both theposition and the

ve-locity of a material particle at the same time The

un-certainty increases as the size of the particle

de-creases

Many researchers have generalized this principle and

restated it in various broader contexts, but most

com-monlyitis brought up when describing the results of

quantum experimental results It is said that these are

determined in part by the point of view and methods

of the researcher For example, iflight is studied as a

particle phenomenon, it appears to behave as a

par-ticle phenomenon If it is studied as a wave

pheno-menon, it appears to behave as a wave phenopheno-menon,

at least as far as the observers and measuring

instru-ments are concerned.Inother words, attempts to pin

down precisely the location of an electron obscures

its energy level, and vice versa, thus challenging the

absolute nature of the world suggested by classical

physics

Heisenberg, Werner(1901-1976)AGerman

physi-cist responsible for deriving a theory ofatomic

struc-ture and proposing the uncertainty principle in 1927,

which has since become widely associated with his

name

Heisenberg built on the work of previous physicists

and mathematicians, including Hermann Weyl For

his contributions, he was awarded a Nobel prize in

1932 In the 1940s, he acted as the director to the

Kaiser Wilhelm Institute for Physics Near the end

of the second World War, Heisenberg was captured

by American troops and taken to Britain When he

returned to Germany, he helped found the facility that

became the Max Planck Institute for Physics

Dur-ing his later years, he was workDur-ing to formulate a

unified field theory of elementary particles

helical antenna, helical beam antennaAnantenna

designed with a helical (spiral) conductor wound in

a circular or polygonal shape The axis ofthe helix is

usually mounted parallel to the ground The

circum-ference size ofthe helix in relation to one wavelength

affects the angle of radiation

heliochrome[sun color]Anolder word for a color

photograph, that is, one photographed in color as

compared to one photographed in grayscale and tinted

by hand using oil pigments Color photography was

not widespread until the 1960s

heliograph [sunwriting]Avisual signaling system

employing light signals, which was established

around 1865 by H C Mance The heliograph took

advantage of the production of glass mirrors in the

1840s to increase the distance over which sunlight

could be reflected It used adjustable mirrors mounted

on tripods and could convey messages in Morse code

in daylight up to about 100 miles

In the United States, leaf shutter versions of the he-liograph were developed to interrupt thelight signals

instead of directing the angle of the mirror as was done with the earlier British heliographs

Most visual signaling systems were superseded by wire telegraphy, but the heliograph survived for sev-eral decades, probably becauseitused Morse, which was then becoming widely accepted, and becauseit required no external power source

Since heliograph signals and microwave transmis-sions share some ofthe same line-of-sight character-istics, heliographs were resurrected to research the placement of microwave relay stations, and the he-liograph is still sometimes used for military communications in regional conflicts where other means of communication are scarce

heliography[sun recording]Atype of early photo-graphic process, also calledsun drawing, which was

pioneered by French inventor, Joseph Nicephore Niepce, in 1816 Originally Niepce used a camera similar to the camera obscura to imprint temporarily

an image of light onto paper coated with silver chlo-ride It was several years before he developed the pro-cess to the point where the image could be perma-nently preserved See Daguerre, Louis; photography

helionicsThe science of the conversion of solar en-ergy to electrical enen-ergy

heliotrope[sun turning]Anearly surveying instru-ment that employed the sun's rays to triangulate from mountain prominences This instrument was devel-oped and used for the highly successful engineering feat ofsurveying India in the 1800s It may also have been used for signaling.Itwas later adapted as a he-liograph by H C Mance in Britain and used for many decades for daylight signaling ofmilitary communi-cations up to 100 miles

helium-neon laser, He-Ne laser Atype oflow power atomic gas laser, now commonly usedinlight shows and monitors This laser produces warm color tones

in the red-orange range but gas lasers with different gas mixes may also produce radiant energy in the blue, infrared, and ultraviolet ranges Until semicon-ductor laser diodes became prevalent, this was the most common commercial laser

The helium-neon laser was described in 1959 and developed and demonstrated in December 1960 by

A Javan, not long after Townes and Schawlow had developed an optically pumped laser The gas laser worked on a different principle from the Townes la-ser, converting electricity to a pure, continuous light beam by passing an electrical current through two inert gases The light is then amplified by reflecting

it between two mirrors at either ends of the laser de-vice

The device was immediately tried for telecommuni-cations The day after the laser was first successfully tested, lavan's lab workers successfully used it to transmit a telephone conversation by converting voice vibrations to light pulses that were detected across the room by a sensor.Inessence, the researchers had

invented his Photophone Despite Bell's great

excite-ment about his invention and his vision of its

poten-tial, he never saw widespread commercial use of the

device due to the difficulty of harnessing a

consis-tent, coherent, sufficiently powerful synthetic source

of light Javan's invention, with the contributions of

W Bennett and D Heriott, made the missing piece

of technology available, a technology that since has

been applied to many technologies in addition to

op-tical communications See carbon dioxide laser,

la-ser history, Photophone

helium recovery In fiber optics preform fabrication

and fiber pulling, helium is commonly used in many

aspects of the manufacture Contaminants are

intro-duced into the helium at different steps along the way

and one-time use of the helium is wasteful For this

reason, manufacturers such as Praxair have developed

draw stations that enable the helium to be recovered,

cleaned, and reused at points where lower purity

he-lium is effective in the fiber fabrication process See

vapor deposition

helix, helical shape A spiral, continuous coil Many

types ofsprings employ a helix shape In radio

trans-missions, a horizontal- and vertical-polarized wave

combined ascircular polarization, is transmitted in

a helical fashion so that it can be picked up by both

horizontal- and vertical-polarized antennas

Hellman-Merkle Atrapdoor knapsack cryptography

system principally designed by Ralph Merkle, with

input from Martin Hellman, who was a collaborator

with Whitfield Diffie on another cryptography

sys-tem The Hellman-Merkle scheme was found to be

breakable and was reported as such in 1982 See

Diffie-Hellman

Hello Protocol In Open Shortest Path First Protocol

(OSPF), a mechanism for establishing and

maintain-ing neighbor relationships Itmay also be used for

dynamic neighbor discovery on broadcast networks

The Hello Protocol elects the designated router on

networks with at least two attached routers

Helmholtz, Hermann von (1821-1894) A German

physicist who expressed relationships between

fun-damental phenomena, such as heat and light, by

treat-ing them as manifestations of a streat-ingle force, a

con-cept we now associate withenergy Helmholtz

fur-ther sought to generalize the concepts put forth by

James Joule Helmholtz encouraged the work of

Heinrich Hertz, who became one ofthe true pioneers

in the discovery of the physical existence and

prop-erties of radiant energy (radio waves)

The Hermann Helmholtz Association of German

Research Centers (HGF) continues Hermann

Helmholtz's tradition by supporting research on

sci-entific' technological, and biomedical topics through

a consortium of centers See Hertz, Heinrich

http://www.helmholtz.de/

henry A unit of inductance in a circuit

(self-induc-tance or mutual induc(self-induc-tance oftwo circuits) such that

the electromotive force ofone volt is produced when

the inducing current varies at the rate of one ampere

per second Named after Joseph Henry

largest indoor/outdoor museum complex in the U.S providing authentic historical artifacts and educa-tional activities Among other fields, it features ex-hibits on the history oftransportation and communi-cation, including Thomas Edison's Menlo Park Labo-ratory The Henry Ford Museum is located in Dearborn, MI http://www.hfmgv.org/

Henry magnet Joseph Henry experimented with electromagnets in the 1820s and 1830s, creating a number of different configurations The Henry magnet

is a type ofexperimental magnet, powered by a 9uan-tity battery, that he called a "quan9uan-tity magnet.' The horseshoe-shaped magnet was wrapped with several layers of insulated wire connected in parallel Henry also experimented with a magnet powered by an in-tensity magnet that could power devices at adistance Henry based his magnets on his studies of electro-magnetism and the work of previous magnet re-searchers As an improvement to earlier attempts, Henry's powerful quantity magnet could transform enough electrical energy into mechanical energy to

be useful Thus, Henry himselfexperimented with the practicability of the electromagnet for powering ru-dimentary telegraphic systems and he communicated his ideas to many eminent inventors who built upon his ideas and put them into commercial use See Henry, Joseph

Henry, Joseph (1797-1878) A gifted American physicist who began experimenting with magnetism

in 1927, Henry produced a high-power industrial electromagnet in 1931 He incorporated his various discoveries into many practical devices, including telegraphs, relays, and electromagnetic motors Joseph Henry actively encouraged and assisted other researchers, in addition to carrying on experiments himself, a fact not always publicly acknowledged by the many inventors who benefited from his generos-ity Morse, Wheatstone, and many other inventors were assisted by the information communicated on both sides of the Atlantic by Joseph Henry

Joseph Henry advocated a science and research fo-cus for the great Smithson endowment that eventu-ally became the Smithsonian Institution, and he was appointed its first Secretary in 1878 He also co-founded the U.S National Academy ofSciences The henry, aunit ofinductance, is named after him (1891 ) See Henry magnet

HEP high energy physics

HEPIC High Energy Physics Information Center.An informational link among worldwide HEP resources

to assist researchers in locating sources and resources One of the services is a global search facility for searching across HEP Web servers that is updated about once per month HEPIC is funded by the U.S Department ofEnergy Division ofHigh Energy Phys-ics It is supported by the Fermilab Computing Divi-sion http://www.hep.net/

hermetic seal Aseal that is airtight and leaktight, and

is sometimes used to preserve a gaseous environment, inside a sealed device, that is different from the gas-eous composition outside Hermetic seals are generally

Fiber Optics Illustrated Dictionary

intended to be permanent Hermetic sealing is used

in a variety of industries, including electronics and

electrical installation

Herrold, Charles D "Doc"(1875-1948)

AnAmeri-can inventor and educator, Herrold is one of the first

experimenters to transmit voice over distance He did

this through Station FN in the Garden City Bank

Building, beginning in 1909 He became known by

amateurs for his station SJN broadcasts When Lee

de Forest's transmitter failed, Herrold provided

mu-sic and news to the 1915 World's Fair about 50 miles

away He had other interests as well and was awarded

a patent for the Arc Phone in 1915 In 1922, he was

broadcasting at 833 kHz through station KQW from

San Jose, California See KDKA, radio history

hertzHz Aunit offrequency expressed as one cycle

per second, named after H R Hertz

Hertz antennaAnantenna system that uses

distrib-uted capacitance to determine its resonant frequency,

which, inturn,is influenced by the physical length

of the antenna This antenna is used in applications

where ground reflection is not a necessary factor for

its functioning Unlike Marconi antennas, a Hertz

antenna is not dependent on the ground or the body

ofa vehicle as a resonant conductor This type

ofan-tenna is common for television and frequency

modu-lated(PM)broadcasts See antenna, Marconi antenna

Hertz, Heinrich Rudolf(1857-1894) A German

physicist who demonstrated important properties of

electromagnetic radiation, discoveries that later

ex-perimenters applied to facilitate the transmission of

radiant energy By 1887, the physical existence of

radio waves had been established He also

contrib-uted a streamlined reformulation ofMaxwell's

equa-tions that was widely accepted The Hertz antenna and

hertz unit of frequency are named after him See

Helmholtz, Hermann

Hertzian wavesElectromagnetic waves in the range

from about 10kHz to 30,000 GHz James

Clerk-Max-well had proposed that rapidly vibrating electric

cur-rents would emit waves, and Hertz experimentally

confirmed this proposition The waves are named

after him See radio wave

Hertzstark, Curt(1902-1988) AViennese inventor

who devised handheld calculator technology that was

patentedinthe late 1930s, but wasn't produced until

the mid-1940s Its accuracy apparently rivaled many

modem devices See Zuse, Konrad

hetero-Prefix for different, other, not usual It is

of-ten used to describe a mix or variety

heterodynel'.t To produce a beat between two

fre-quencies, which could be of various kinds: audio,

optical, or radio In radio heterodyning, an electrical

beat can be selectively created and controlled by

het-erodyning a received signal current with a steady

in-troduced current The frequency thus formed can then

be further processed by amplification, as in repeater

stations or filtering See beat, beat frequency,

hetero-dyne repeater

heterodyne repeaterA frequency repeating system

commonly used in the propagation of radio signals

that uses heterodyning to create an intermediate

fre-quency through demodulation, which is amplified, modulated, and retransmitted over the next leg This technique is less subject to distortion and loss through modulation/demodulation than baseband repeating Heterodyne repeating may be used in conjunction with baseband repeating if the signal is traveling through several legs and some channels need to be dropped offat the baseband stations See Armstrong, Edwin H.; baseband repeater

heterojunction In semiconductors, a common dy-namic junction, usually of p-n type, in which the materials on either side of the junction are substan-tially different See homojunction, p-n junction

beterojunction laserAsemiconductor laser compo-nent that has been designed to reduce losses result-ing from light diffraction within the optical reflec-tive cavity by engineering the p-n junction width and the index of refraction of the cavity By replacing some ofthe materials in the junction so that the junc-tion is not homogenous, the index of refracjunc-tion can

be reduced to retain more light within the reflective optical cavity, reducing losses This is more efficient than the traditional homojunction laser diode

Itis also possible to retain the materials in the junc-tion but replace the materials in the p-n regions, but this may be so effective in confining the light energy within the cavity that it may damage the component There is a happy medium between laser efficiency

in terms of producing photons, and confinement in-efficiency to allow the light to escape from the cav-ity before it damages the component itself Larger optical cavities with different layers are one strategy for increasing efficiency without destroying the com-ponent from within See homojunction laser, semi-conductor laser

heuristic problem-solvingAnexploratory problem-solving strategy that employs successive trial and evaluation of the results in such a way that the re-sults can be used in the subsequent trials to "home in" on a solution Heuristics are often used in artifi-cial intelligence programs where the result is not known in advance, and where brute force methods are inappropriate due to the large number ofpossible choices and outcomes Chess playing programs, for example, use a combination of heuristics to handle novel situations and databases of known moves and strategies Heuristics are common in robotics, where

a robot may have to interact with an unknown or un-predictable environment See algorithmic problem-solving, brute force problem-problem-solving, neural network

Hewlett, WilliamR (1913-2001) AnAmerican in-ventor and business tycoon, Bill Hewlett was a founder ofHewlett-Packard along with David Pack-ard An instrumentation engineer, Bill Hewlett in-vented an audio oscillator which was used by Disney

Studios in the production ofFantasia He was a past

president and director ofthe Institute ofRadio Engi-neers (now the IEEE), an honorary trustee ofthe Cali-fornia Academy of Sciences, and held many other professional and civic leadership positions Apromi-nent Silicon Valley pioneer and philanthropist, Hewlett was known personally by many ofthe

promi-puter revolution.

Hewlett-Packard Company HP In 1938, Dave

Packard and Bill Hewlett, both graduates of Stanford

University, began working out of a garage in Palo

Alto, California Their first product, an audio

oscil-lator resulting from Bill Hewlett's research of

nega-tive feedback, was designed to test sound equipment

It was a new type of design, utilizing an

incandes-cent bulb to provide variable resistance This

prod-uct was followed by a harmonic wave analyzer Their

first big client was Walt Disney Studios Disney

or-dered eight oscillators for the production ofthe movie

Fantasia.

From these beginnings, Hewlett and Packard formed

a partnership on New Year's Day in 1939; a toss ofa

coin decided the company name HP was officially

incorporated in 1947

Since then Hewlett-Packard has become a

well-known supplier of calculators, computers, software,

printers, and other accessories to the computing

in-dustry The firm is known for good quality products

(their calculators have been known to survive the

"drop-kick" test) and a corporate culture that seems

to produce happier employees than many other

com-panies in the industry

In 1996, David Packard, successful businessman and

philanthropist, died at the age of83, followed by

Wil-liam R Hewlett, in 200I

HF,hf I hands free 2 See high fidelity 3 See high

frequency

HFCSee Hybrid Fiber Coax

Hi bandA video standard developed by the Sony

Corporation in 1989 to support 500 lines of

resolu-tion on a TV screen This resoluresolu-tion falls between

NTSC and High Definition Television (HDTV) See

Hi8mm

Hi-BandIRAninfrared-remote technology used for

remotely controlling a variety of consumer devices

such as car stereo systems

Hi-OVISHighly Interactive Optical Visual

Infor-mation System A Japanese cable television delivery

system employing different types ofcable for

differ-ent parts of the service network

Hi8mmA high-quality, analog, tape-based compact

video system developed by Sony, Hi8mm became

especially popularinthe late 1990s Hi8mm has many

benefits, including small cassettes, only 2.5 x 3.6 in

for two hours ofrecording/playback at regular speeds

The long play time gives Hi8mm an advantage over

S-VHSc (compact S-VHS) The small cassette

for-mat enables video camcorders and playback decks to

be compact as well The sound quality is excellent,

compared to older technologies, and features stereo

sound, though not all Hi8mm camcorders have two

microphones The video resolution of 400 lines and

signal-to-noise ratio of 40 to 50 dB are equal to

S-VHS and far superior to 240-line 35 to 45 dB S-VHS

formats

For analog recording, Hi8mm is likely to remain a

viable, favorite format for a while longer, but digital

camcorders are catching on quickly and will

prob-tion, CD-quality sound, and digital nonlinear editing capabilities without conversion

HiFDA 3.5-in floppy diskette system developed jointly by Sony and Fujifilm, introduced in 1997 HiFDs are double-sided, with a magnetic storage ca-pacity of up to 200 megabytes

hibernationA resting state, one of low energy us-age and activity A term often applied to the sleep mode on portable computers, which powers down during times oflow activity to extend battery life Hi-bernation has also long been applied to software ap-plications that lie dormant waiting for some event causing them to become active, or to run at a higher priority level The event that rouses the program can

be many things, including the time ofday, input from

an interface device such as the mouse or keyboard, activity of users, or data from another program See sleep mode

hickeyA spot, halo, or other imperfection in the ink

or toner of a printout caused by undesired extrane-ous particles, dried ink, etc

Hicks, John Wilbur "Will"AnAmerican physicist and inventor, Hicks was one of the many optical re-searchers who worked at one time at American Opti-cal After leaving the company to cofound Mosaic Fabrications, Inc., with P Kiritsy, in the late 1950s,

he was approached by John Johnson about the po-tential offiber optic filaments for lengthening a light path through fiber optics rather than through longer tubes Hicks succeeded in pulling optical fibers, in making fiber-based vacuum assemblies and, in col-laboration with B Gardner, in developing fiber op-tic faceplates (arrays of aligned bundles of fibers) which were all significant innovations at the time He maintained close ties with American Optical (AO)

In 1961, he worked with Elias Snitzer at AO to dem-onstrate the dielectric waveguide properties of opti-cal fibers so small, they would carry light in a single wavelength mode

Hicks' interest in fiber optics hasn't waned Many of his visions of fiber have come true and he continues

to promote an optimistic viewpoint of widespread data-over-fiber availability He has been involved with a number ofcompanies and has continued to ten-der proposals for fiber-based technologies through American Micro-Optical, Inc See Johnson, John; Kawakami, Shojiro; Kao, Charles K.; Snitzer, Elias hierarchyA group of items, people, or processes or-dered according to some type of structure or rank, usually top-down or bottom-up A hierarchy may be nested Hierarchies are generally designed to facili-tate the location of some item within the hierarchy

or to simplify the understanding of its contents People in an organization, and files or discussion groups on a computer or network system are often assigned positions within hierarchies

High Altitude Long EnduranceHALE Pilotless platform crafts intended to float above commercial aircraft at about 20,000 meters, which have been pro-posed as two-way communications links capable of carrying phased antenna arrays The HALE systems

Fiber Optics Illustrated Dictionary

are experimental and a number of systems from

he-lium to jet-engine propulsion have been proposed

The cost relative to traditional satellites makes HALE

transceivers attractive to developers Actual

deploy-ment of these systems has to take normal aircraft

safety and traffic patterns into consideration

high ASCIIThere really isn't such a thing, since

ASCII defines the lower 128 characters~Oto 127),

but "high ASCII" and "extended ASCII' are often

used to describe characters above decimal values of

127, which are different on each system See extended

ASCII

high bandwidthslang Descriptive of a person with

high level, wide-ranging intellectual abilities The

author first heard this phrase in the early 1980s among

hard-core programming friends in computer users

groups and suspects it originated spontaneously in a

number of places and subsequently spread through

networks such as Fidonet Other computer-related

terms that have been applied metaphorically to

hu-man intelligence includehigh baud rate, high clock

speed, and multitasking.

high bit-rate Digital Subscriber LineHDSL A

digital transmissions technology that can transmit

DS-l or E-l transmissions for longer distances over

the traditional, unshielded twisted-pair wire that is

widely installedintelephone circuitry HOSL is

typi-cally used in digital loop carrier systems, private

branch networks, and cellular antenna systems

Un-like earlier technologies, HDSL transmits over

mul-tiple lines without repeaters and uses techniques to

pack more information in less bandwidth It provides

rates up to 1.544 Mbps over DS-l or 2.048 Mbps over

E1inthe 80 to 240kHzbandwidth range See

Digi-tal Subscriber Line, DS-

High Definition TelevisionHDTV.In1987, the

Fed-eral Communications Commission (FCC)

acknowl-edged that the NTSC television was out of date and

formed an Advisory Committee on Advanced

Tele-vision SeIVice (ACATS) to recommend a revised

tele-vision standard for the U.S Most of the improved

systems proposed to the FCC were analog or hybrid

analog/digital The FCC stated a preference for a

si-mulcast HDTV system and identified four digital

sys-tems These were extensively analyzed, leading to an

ACATS recommendation that digital HDTV should

be adopted In 1993 an alliance was formed in

coop-eration with ACATS to create an HDTV system,

re-leasing specificationsin1994

high Earth orbitHEO An orbiting region around

the Earth into which certain types ofcommunications

satellites are launched There are advantages and

dis-advantages to high orbits The main advantage is that

it takes fewer satellites to provide global coverage

Disadvantages include the higher cost of launching,

the higher amplification needed for signals to travel

the greater distances, and the effects ofradiation The

lifespans of high-orbit satellites tend to be around

twelve to fifteen years Most high-orbit satellites

travel at about 20,000 to 40,000 kilometers outside

earth High Earth orbit satellites are typically used

for geostationary satellites such as theu.s. Global

Positioning System (GPS) See low Earth orbit, Glo-bal Positioning System, medium Earth orbit high fidelityA playback system that reproduces the original so well that it is indistinguishable, or almost indistinguishable, from the original source This qual-ity is often accomplished through fast transmission and wide bandwidths In audio systems, high fidel-ity is frequently abbreviatedhi-fl.

high frequencyA signal frequency defined as the range from 3 to 30 MHz

High Level Data Link ControlHDLC An lTU-T standard bit-oriented data link layer communications protocol originally developed by ISO for managing synchronous serial transmissions over a link connec-tion In HDLC there are separate bit patterns for con-trol and data representation

high level languageA computer programming lan-guage at the user level, designed to be as close to a natural language as possible and generalizable to a variety of platforms FORTRAN, BASIC, and

co-BOL are probably the best-known and most widely used high level languages High level languages are often interpreted, but may be compiled for the spe-cific platforms on which they will be running As lan-guages become closer to machine level, they also tend

to be more symbolic and, thus, more difficult to read and write They also increase in platform-depen-dency For contrast, see assembly language, low level language, machine language

high pass filterA filter designed so it doesn't pass waves below a specified cutoff frequency (greater than zero), and the transmission band extends upward indefinitely from that cutoffpoint See low pass filter High Performance Computing ActAnact of the U.S Congress which was passed in 1991 to facili-tate and promote the development and evolution of interconnected computer networks serving educa-tional institutions, research laboratories, and industry High Sierra standardA compact disc standard in-troduced in 1986 by the High Sierra Group (named after the hotel and casino at which the group met) It was subsequently adopted by ECMA (ECMA-119) and ISO (ISO 9660) and released with slight revi-sions See ISO 9660

High Speed Data UnitHSDU Aphysical data com-munications device to provide a high-speed data channel together with control signals from, for ex-ample, a serial connection HSDU may be software configurable and may operate in synchronous or asynchronous modes or both

High Speed Internet Access Asummary ofinfonna-tion published about high speed Internetworking, published monthly by Information Gatekeepers, Inc high speed networkingThis is a relative phrase and will change as the technology advances but, in the mid-1990s, high speed networking was generally considered to be around or over 100 Mbps Examples ofhigh speed network technologies include asynchro-nous transfer mode (ATM), Fast Ethernet, and Fiber Distributed Data Interface (FOOl)

High Speed TechnologyHST A U.S Robotics pro-prietary, high-speed, full duplex signaling and error

factures modems complying with this protocol and

some dual-standard modems that are both HST and

V.32 bis capable See Microcom Networking

Proto-col, modem,VSeries Recommendations

High Speed Token-RingHSTR.Anenhanced

com-mercial Token-Ring technology developed by

Inter-national Business Machines (ffiM) HSTR can run

Token-Ring and Ethernet on one medium, support

source routing through data packet headers, and was

based on existing standards, including Fibre

Chan-nel Aimed at a market similar to Ethernet, HSTR

appears to be primarily supported by those

upgrad-ing legacy Token-Rupgrad-ing systems See Token-Rupgrad-ing

high usage groupsIn the telephone industry, high

usage groups are trunks between main switching

of-fices that are established as priority routes to handle

the majority of transmissions High usage trunk

groups are intended to hand off overflow traffic to

alternate trunks See erlang

high-threshold logicHTL A concept used in

phys-ics and electronphys-ics especially with regard to computer

circuit designs Voltage thresholds are voltage levels

at which more or less voltage may have no further

effect or at which more or less voltage (at the high or

low thresholds, respectively) could damage a system

or render it inoperable They are also points at which

state changes may occur due to unconditioned or

noisy signals In transistor-based devices, the

thresh-old voltage is related to performance levels and is

often used to control the characteristics and

opera-tion ofa system Convenopera-tionally, on portable devices,

lowered power is associated with degraded

perfor-mance and power leakage However, the use

ofhigh-threshold transistors is seen as one means to extend

battery life on low-power devices, such as cellular

phones, while in standby power mode without

ad-versely affecting performance

High-Density Bipolar3 See HDB3

High-performance Network ForumHNF

Devel-opers and promoters of the HIPPI GSN standards

European High-performance Network Forum

(EHUG) works in cooperation with HNF and

coor-dinates an annual network technical symposium

http://www.hnt:org/

high-resolution direct core monitoringHDCM A

commercial software imaging process for fiber optic

fusion splicing systems such as the Micro-Core™

Alignment Fusion Splicer.Itfacilitates core alignment

prior to splicing and splice loss estimates after splicing

highllow tariffA charge that is selectively made

ac-cording to a type or level of service For example,

some Internet Service Providers (ISPs) charge

differ-ent rates for connection time depending upon the

speed at which the subscriber's modem connects A

bulletin board service (BBS) may quote two levels

of service depending upon whether or not the user

wants to access the games sections In phone services,

two prices may be quoted for a subscriber call, one

cost per minute over high density trunks and a

dif-ferent cost per minute over low density trunks

HIPERLANhigh-performance radio local area

net-(LANs) that are interconnected through radio fre-quency transmissions rather than through wires Un-like North American radio-based LANs, that are largely based on sharing unlicensed 900-MHz and 2.4-GHz spectrums, HIPERLAN was allocated dedi-cated spectrums in the 5.15- to 5.30- and 17.1- to 17.3-GHz frequency regions by CEPT, in 1992 A draft standard was developed by ETSI and presented

as a functional specification in 1995 The availabil-ity of dedicated bandwidth increases the probabilavailabil-ity

of reliable service with less chance of outside inter-ference See air interface, local area wireless network

HIPPIHigh Performance Parallel Interface HIPPI

is a point-to-point high speed data transfer technol-ogy created at Los Alamos in the 1980s HIPPI oper-ates over twisted-pair copper cable for distances up

to 25 to 50 meters (longer with cascaded switches) and distances up to 300 meters, or 10 kilometers over multimode or single-mode fiber cables

HIPPI was originally developed for supercomputing applications but is starting to be adapted to other en-vironments with the dramatic drop in price of the technology, particularly the switches Transmission speeds include 800 Mbps and 1.6 Gbps (simplex or duplex) HIPPI can be employed with SaNEr over distances and over satellite transmission links HIPPI

is an ANSI standard with a series ofdocuments spell-ing out the standard and its various switchspell-ing and encapsulation characteristics See HIPPI-6400

HIPPI-6400, SuperIDPPIHigh Performance Par-allel Interface Officially it is now known as Giga-byte System Network (GSN) Avery high bandwidth, low latency network transmission technology which offers gigabytes-per-second transfer rates, much faster than the capacity ofGigabit Ethernet, ATM, or Fibre Channel Based on the HIPPI standard, but with enhancements in error correction and lower latency rates, HIPPI-6400 uses a fixed-length cell of32 bytes Transfer rates that are as fast as, or faster than, the internal workings ofan individual computer on a net-work will change computing in a significant way With this development, the network is no longer a bottleneck and individual computers attached to the network can theoretically function as individual parts

of the same organism, that is, as a massively parallel computing system Fast transfer rates with high band-width also make it easy to support a diverse variety

of protocols, providing flexibility SuperHIPPI can support applications like uncompressed digital movies and HDTV signals See HIPPI, Scalable Coherent In-terface

Hirschowitz, Basil Isaac(1925- ) A South African physician and educator who traveled first to the U.K., then to the U.S where he became a professor ofmedi-cine Hirschowitz visited Hopkins and Kapany in London at the time they were conducting pioneer re-search on the use of fiber optics for medical viewing instruments, in 1954 Along with C Wilbur Peters,

he undertook a project to develop a flexible fiber op-tic endoscope, hiring Larry Curtiss to assist in the work The resulting instrument aligned the optical

Fiber Optics Illustrated Dictionary

fibers by embedding them in a glass matrix with a

low refractive index to facilitate total internal

reflec-tion The instrument was first used with a patient in

1957 The Hirschowitz endoscope is now in the

Smithsonian Institution collection See Kapany, N;

Hopkins,H.

Historic Speedwell Located in New Jersey, this

mu-seum features telegraph history through the daily life

of the Vail family and their association with Samuel

Morse Morse had a close association with the Vail

family who provided space, materials, and expertise

to assist him in fabricating the inventions for which

he is known The Vail family is also known for the

great successbfAT&1.See Vail, Alfred; Vail,

Theo-dore

hits I A quantitative expression ofthe number

ofsys-tem or application accesses ofa specified type within

a specified time period 2 The number of attempts

of illegal entry to a system within a specified time

This information is used to gauge security needs and

adjust procedures, ifnecessary 3 The number of

suc-cessful accesses of a database or a Web site

HNF See High-performance Network Forum

HNS See Hughes Network Systems

HOBIS Hotel Billing Information System

Hockham, Gearge A Along with CharlesK.Kao,

Hockham authored "Dielectric-Fiber Surface

Waveguides for Optical Frequencies" in Proc IEEE

(1966) Together they promoted the concept of

re-moving impurities from optical transmission glass to

reduce loss and increase transmission, an idea that

made fiber links a practical reality

Hodgson, James (1672-1755) A British

mathema-tician and lecturer, Hodgson was evangelizing

scien-tific achievements at an important time in history

when many significant historical figures, including

Isaac Newton, Defoe, Hauksbee, and Boyle, were

in-fluencing the future of science and trade Hodgson

had been an assistant to the Astronomer Royal

Flamsteed since 1696, but left that position in late

1702 to become a lecturer

Hodgson was versed in natural philosophy,

experi-mental science, and mathematics, and joined Francis

Hauksbee the Elder at the Royal Society during its

leadership by Newton In 1703, he became a fellow

of the Society

As a lecturer, Hodgson advertised seminars in

as-tronomy and philosophy promoting the discoveries

of members of the Royal Society and demonstrated

experiments Hodgson began to write technology

books by 1704 and apparently also tutored in the

sci-ences Hauksbee, a demonstrator for the Society, had

an interest in these lecturers and the two began to

work together, thus creating a forum for practical

embodiments of Newton's theories and some of

Hawksbee's own inventions In 1706, Hodgson

pub-lished The theory of navigation demonstrated In

1709 he became a mathematics master at the Royal

Mathematical-School in Christ-Hospital In 1736, he

published The Doctrine ofFluxtions Founded on Sir

Isaac NewtonsMethod, one of the early textbooks

on calculus

Hodgson was an important impetus in bringing ex-perimental science (which was still a relatively re-cent concept) and mathematics to the common man, primarily merchants, navigators, and tradespeople who recognized the value ofnew technologies to their professions He was also one of the first to voice the basic principles of sonar, suggesting that sound could

be used to estimate the distances of ships at sea and ofland objects See Hauksbee the Elder, Francis Hoff, Marcian Edward (Ted), Jr (1937- ) An American engineer who, in response to a request from

a Japanese company for a calculator chip, designed the Intel 4004, in 1971 This highly significant inven-tion was the first commercially successful micropro-cessor chip, and it launched the microcomputer in-dustry

Hoffbecame a manager in the Applications Research division of Intel Corporation in 1968 and joined the

4004 development project In 1983, he became Vice President ofAtari, Inc., which was well known at the time for home computer systems and, in 1984, was awarded the IEEE Centennial Medal In 1990, he was appointed Chief Technologist at FTI Teklicon, Inc hold I To pause, to cause to remain in a particular position or situation 2 While attempting a computer

login, the user may be queued or put on hold until

fewer users are on the system This hold usually mani-fests as a pause after typing the username or after typ-ing the usemame and password On popular archive sites, there may be a hold period or increased lag time while accessing a system Sometimes it's better to log

on later during off-peak hours, or to find a less busy

mirror site,if one exists 3 On phone systems where the receptionist is busy with other calls, or the auto-mated system is queuing the caller for the next avail-able operator, the user is usually put on hold, some-times for extraordinarily unreasonable lengths oftime (especially if it's a long-distance call) On systems that don't have music or a recording informing you that you are in the queue, it is sometimes difficult to know ifyou are still on hold or have been cut off On multiline systems, a call can often be put on hold by one individual and picked up by another (line hold)

On some systems, the hold call can be continued only

on the main console or by the person originally put-ting the call on hold (exclusive hold)

Hold Recall An optional telephone feature that alerts you to the fact that someone is on hold On most multiline systems and some residential phones, the line on hold will be identified by a flashing LED or,

on more sophisticated systems, with beeps or voice messages

hold time 1 In circuits, the time interval after the clocking of a trigger circuit during which data must remain unaltered 2 In welding or soldering, the time during which the welded object must be held rela-tively steady in order for the weld or solder to harden

3 In telephony, the length of time a caller is kept waiting, and waiting

holding beam A diffused electron stream used to re-generate charges applied to the surface of a storage tube

tional coil in a relay for each direction ofa

transmis-sion that can be opened or closed independently of

the main circuit to enable a single circuit to

accom-modate alternate two-way communications

of the electrons that make up the holding stream

holding time In telecommunications, the entire

du-ration of a call from the time the connection is

re-quested until it is completed and disconnected The

actual time during which the connection is

estab-lished is only a portion ofthe holding time, although

it's usually the time that is billed Holding time is

important, for example, in tracking sales calls How

long does the sales representative or telemarketer

ac-tually stay on the line trying to connect a call and

handle the entire transaction, as opposed to the

amount of time actually spent with the customer? If

there is a large discrepancy, another method may

need to be tried

Holding time is also important in computer or

tele-phone circuit planning and management because the

time spent connecting and queuing the caller may

affect capacity and efficiency as much as that

por-tion ofthe call during which the communicapor-tion takes

place

holding trunk In telephone communications, a

queue wherein a call is held until availability is

es-tablished or an alternate route is found

holiday factor Aconcept in service and retail

indus-tries (including Internet services) that accommodates

changes in rates of service use or product purchase

during holidays The transportation, retail, and

tele-communications industries tend to have patterns of

higher usage during holidays and need to factor in

extra staff, lines, products, etc to handle the demand

Holidays may also create decreased demand, in

which case shutdown or reduction ofunneeded

sys-tems may result in cost savings

Hollerith card Historically, a sturdy, rectangular,

piece ofcard stock organized into rows and columns

that were individually labeled and further organized

into sections Acircular hole was punched in the card

to select the coded data in that region ofthe card The

punched holes could later be read and decoded to

re-assemble the original information This concept was

born out of the cards used to store loom patterns on

Jacquard looms In the 1920s, ffiM, the

evolution-aryheir to the Hollerith Tabulating Company,

intro-duced a patented rectangular hole that made it

pos-sible to encode almost twice as much information as

the original round hole cards

Hollerith cards were used to store historic

comput-ing machine code in the days before tape, diskette,

and hard drive storage The punched card was, in

ef-fect, a binary storage system with the unpunched or

punched locations representing off or on and

corre-sponding to no or yes responses to a predefined

pa-rameter

As the storage capacity of these cards was quite

lim-ited, many cards were needed to store a body of

in-formation Punch cards, in general, can be fully

cal devices, or partially punched to provide a record without the mess and waste ofchad and read again

with sensing devices.Inthe case of Hollerith cards, the punched cards were read by an electrical reader that completed a circuit and activated a relay when a pin passed through a portion of the card with a hole With the use ofgang punches with selectable

tem-plates, up to 40,000 cards a day could be punched The computer cards commonly used in library books, until bar codes became prevalent in the 1990s, are descended from Hollerith cards See Hollerith Elec-trical Tabulating Machine, Jacquard 100m, zero punch

Hollerith code A 12-1evel code designed by Herman

Hollerith in 1889 for use on Hollerith cards which,

in tum, were used with the Hollerith Electrical Tabu-lating Machine The card is sectioned and labeled and the code was implemented in the form of holes punched at specified intervals in designated rows and columns, with each columncorrespondin~ to an al-phabetic or numeric character, in order to form a semipermanent record that could be read and inter-preted in the future This code was widely used in early computing days to store program instructions and data Over time, variations were developed and EAI and ANSI standards were established to govern the configuration ofthe cards, holes, and data encod-ing

Hollerith code survived much longer than the Hol-lerith Machine, which was superseded by electronic computers Hollerith code continued to be used in microfilm records, e.g., for storing microfilm image data and is still covered in Information Technology (IT) courses For the processing of textual informa-tion, it has been superseded by other systems, includ-ing EBCDIC and ASCII See Hollerith Electrical Tabulating Machine

Hollerith Electrical Tabulating Machine A

me-chanical-electrical data processing mechanism for quickly and accurately recording and classifying in-dividual data from a variety ofsources It was devel-oped by Herman Hollerith in the early 1880s Hollerith's machine came to prominence when it was selected (over a system developed by A Graham Bell) to tally the results of the 11th U.S Census, in

1890 Before Hollerith's invention, it had taken al-most a decade to process the results ofa U.S census With the use ofthe Tabulating Machine by the Popu-lation Division of the Census Office, thousands of entries could be tabulated in a single day, thus greatly expediting the recording ofover 60 million cards, one for each person included in the census The 1890 cen-sus was processed in only a year

The Census Office continued to use the Hollerith Machine for further statistical analysis ofspecialized groups within the population For example, in 1901, Bell was using the Hollerith machine to compile and process information from the census relating to the blind and deaf, with assistance from his wife on se-lecting and organizing the format and priorities re-lated to the data (an important aspect of setting up

Fiber Optics Illustrated Dictionary

the punch configuration and tabulation) After the

census, other organizations with statistical tabulating

needs looked into the use of the machine, including

accounting and transportation firms

There were two main aspects to the Hollerith

Ma-chine: the adjustable punching mechanism for

creat-ing the data cards and the electrical pin-based

read-ing mechanism for processread-ing the cards, activatread-ing

relays, and incrementing a counter The letters and

numbers organized on the punch mechanism's

key-board could be altered to suit the type ofdata that were

being entered

The Hollerith Machine received much publicity as a

result of the 1890 census and caught the attention of

other institutions,especi~illy statistical and auditing

companies and departments Variations and

improve-ments were developed, with the tabulating and

sort-ing functions sometimes implemented separately and

sometimes housed in one unit

The Hollerith mechanical tabulating mechanism was

to be an important impetus in the development of

advanced calculators, the forerunners to early

com-puters See Harvard Mark I; Hollerith, Herman;

In-ternational Business Machines

Hollerith Tabulating Data Card

A sample ofa punched Hollerith card in which the

card has been organized in sections and labeled with

alphabetic or numeric markers [Railroad Gazette,

April1895.]

en-gineer who devised a historic tabulating machine, in

1884, which he further developed with the concept

ofpunched cards as an information storage medium

In 1889 he received a patent for his machine to

com-pile statistics (U.S #395,782) Hollerith was

subse-quently contracted to carry out the storing and

read-ing of U.S census information, beginnread-ing with the

1890 U.S census Following the success of this

in-vention, he fonned the Tabulating Machine Company,

in 1896, to market the technology.In1911, it was

merged with other companies to become the

Com-puter Tabulating Recording Company, the historic

beginnings of International Business Machines

(mM) See Hollerith Electrical Tabulating Machine

hologram A type of imaging using lasers, based on

the recording of an optical interference pattern

produced by the interaction of two or more waves from the same source The effect of viewing a holo-graphic image is a sort of3D, when moving the head around and focusing on different parts of the image

In most cases,itis not fully a 3D effect, as the image

is usually recorded on some flat (with transparent depth) medium such as glass or transparent plastic (although the technology itself is not limited to this form of presentation) The image is typically more ethereal than a photograph, since it is viewed through

"layers" of the transparent medium Projected ho-lographic images hold great promise for 3D virtual reality, and scientists have been working on holo-graphic memory modules for computers that poten-tially can store enormous amounts of information in small three-dimensional components It has been sug-gested that human memory may share some func-tional similarities with holograms

Hollerith Tabulating System

The Hollerith Electric Tabulating System showing the punch on a movable arm poised over the card holder and a lettered and numbered keyboard hole alignments for the various data that were to be en-tered and stored on punched cards [The Manufac-turer and Builder, J( 22, 1890.J

A Hollerith reader, the sorting and tabulating mechanism that was used to process the individual cards into statistical data once they had been punched with information relevant to the application [Rail-road Gazette, April 1895.}

home Incomputer interfaces that distinguish regions

ally designated as thehomeposition, that is, a

posi-tion to where a pointing device may return, or where

a cursor might start again after the region has been

cleared or a new window opened

On English language-based systems, for example, the

home position in a text window is usually the top left

corner If the text were being typed in another

lan-guage that tracks from right to left, such as Hebrew,

the home position would be the top right of the

win-dow or screen, or bottom right if it is bottom to top

reading.InPostScript page layout programming, the

home position is generally considered the bottom left

comer, as it is with a number ofprinter graphics

lan-guages Some systems have ahomekey as a one-step

shortcut to position the cursor in the home position

home ATM network HAN Abroadband home

net-work providing connectivity with avariety ofservices

and devices (computers, television, appliances, etc.)

See ATM Forum, fiber to the home, RBB

home page AWorld Wide Web concept referring to

the fIrst, primary, or main page of a set of hypertext

linked pages on a particular host, or belonging to a

particular individual or organization Web pages are

not inherently hierarchical, since any page can link

to any other, but humans tend to grasp concepts more

easily when information is organized in a top-down

or bottom-up manner, and home pages reflect our

preference for this type of organizational structure

A home page serves as a jumping off point, table of

contents, or general site information map to help

navi-gate the rest of the links Commercial sites tend to

have home pages that showcase product information

and entice the user to explore the rest ofthe site

Per-sonal sites often show family relations, professional

credentials, and personal interests Educational home

pages usually provide information on course

offer-ings, faculty, and facilities See HTML, hypertext,

World Wide Web

home run Acentralized wiring topology, like a star

topology, in which cables to individual units or

con-soles all lead back to the central switching system

Most private branch systems, almost all key systems,

and many of the smaller computer network systems

have this type of cabling arrangement In home run

wiring, which has little or no redundancy, a severed

line will cut offthe end station from all other stations

See topology

Homebrew Computer Club A historic, influential,

electronic thinktank and tinkerer's organization,

founded in California in 1975 Steve Wozniak is one

of the most famous of the Homebrew members The

Altair was demonstrated at a Homebrew meeting,

with homebrewers jumping on the opportunity to

write applications for this early computer

homeostasis A state in which there is a tendency

to-ward balance, stability, or equilibrium A state in

which there is no change

homing I Zeroing in on an intended destination or

target 2 Approaching an intended destination by

holding some parameter ofnavigation constant (with

the exception of altitude) 3 In guidance systems,

der to locate a target Bats and missiles use homing systems 4.Intelecommunications, homing is the se-lection of a route through which a call can be set to the next switching center, especially in toll systems, which may pass through several specified switching stations

homodyne reception See zero beat reception homojunction A mechanism within a semiconduc-tor in which the layers comprising either side of the junction are substantially formed ofone material For dynamic processes to occur within traditional semi-conductors (those dependent upon materials rather than the composition of the layers), however, there needs to be some difference between the two layers associated with the junction such as differences in con-ductivity or doping Doping, the impregnation of impurities with particular properties, creates a dy-namic imbalance between the layers to facilitate en-ergy transfer and release ofphotons, for example and

it can reduce the contact resistance between the semi-conductor and a metal contact, creating an n-n+ junc-tion See heterojuncjunc-tion

homojunction laser A basic semiconductor laser with a single semiconductor material for the p-n junc-tion doped to produce the dynamic energy transfer effects ofthe junction The index ofrefraction is con-trolled by the type and amount of doping This pro-duces an effective laser, but some of the light is lost due to diffraction, so it is not ofthe highest efficiency See heterojunction laser, semiconductor laser Honeywell Kitchen Computer Honeywell, in a blaze of optimism that is unique in entrepreneurial history, introduced one of their Series 16 computers

as a home computer for the kitchen through the Neiman Marcus catalog for $10,000, in 1969 It could store recipes, was programmable, and included kitchen accessories To put the priceinperspective,

it cost roughly the same as four new cars or a small starter home, or five years' gross wages for a person earning minimum wage Even now, almost halfa

cen-turylater, there are few computers in kitchen envi-ronments, and it would be incredibly difficult to sell one for the modem equivalent of $80,000 As you might expect, the Kitchen Computer flopped The Series-16 computers, from which the Kitchen Computer was born, were originally designed by Computer Control Company and bought out by Hon-eywell They were released at about the same time

as the Digital Equipment Corporation (DEC) PDP-8 minicomputers The Series-16 computers included the DDP-116 (1965), the DDP-516 (1966), and the DDP-316 (1969) The DDP-316 was essentially a physically reduced-size version of the DDP-516 By 1960s standards, the 316 line would probably be con-sidered minicomputers, as they had 16-bit registers, with core memory and a memory read/write time of between 1 and 2 microseconds, which was pretty good compared to the low-cost microcomputers that came out a decade later The main unit ofthe smaller models was about the size of a deep 17" CRT moni-tor Like the later Altair, the units had lots ofswitches