Due to the increased speed of transmission over serial communications, parallel ports are commonly used for outputting to printers and other types of peripherals like cartridge drives..
Trang 1Fiber Optics Illustrated Dictionary
Parabolic Antenna Examples
This roofmounted parabolic antenna is about 81eet
across and uses a mesh parabola to reduce weight and
wind resistance.
the motion of objects and are used in the
manufac-ture ofreflectors and antennas See parabolic antenna,
parabolic reflector
concentrate and direct reflecting beams See parabola, parabolic antenna
paradigm A clear or typical example, a standard,
ideal, or archetype
paradigm shift Afundamental, significant change in
the way something is perceived or understood, par-ticularly if it has been taken for granted, or assumed
to be true for a long time, or by a majority ofthe popu-lation.ln other words, the situation or thing itselfhas not changed, but our way of understanding it has
A general paradigm shift occurred when humans, most ofwhom believed that the Earth was the center
of the solar system and even the universe, acknowl-edged that the Earth revolves around the sun The dis-covery that matter at the atomic level (quantum me-chanics) did not behave according to accepted mod-els of classical mechanics represented a paradigm shift in physics Paradigm shifts often take a long time, sometimes decades or centuries (although tran-sition periods are collapsing as education and televi-sion become widespread), and those who first pro-pose new ideas and ways of looking at things are of-ten pilloried or persecuted (even beaof-ten to death or hanged) for their assertions The suggestion that com-puters could be taught to be "intelligent," or to play games intelligently, was met with almost universal contempt in the 1960s and 1970s.In1997, a computer beat a grandmaster chess player, an event that added credence to the argument that intelligent computers could be developed, and may someday surpass hu-mans in specific or generalized intelligence, or de-velop machine intelligence of which humans are not capable
parallel port An interface port on a computing
sys-tem that permits the connection of parallel devices for the simultaneous transfer of data across multiple transmission wires Most microcomputers are now standardized to 25-pin parallel D connectors, com-municating with Centronics-compatible parallel pro-tocols (although there are individual makers who use slight variations ofthe standard) Due to the increased speed of transmission over serial communications, parallel ports are commonly used for outputting to printers and other types of peripherals like cartridge drives See serial port
parallel processing Carrying out two or more tasks,
more or less concurrently, usually with the intention
of carrying out the processing at a faster speed, or otherwise more efficiently See concurrent program-ming
parameter A property which records, embodies, or
determines a characteristic of an object or system In communications, parameters affect many character-istics such as size, shape, speed, timing intervals, ad-dresses, identities, etc
parametric amplifier A type oflow noise,
radio-fre-quency amplifier which employs high-freradio-fre-quency alternating current (AC) for power Used with micro-wave frequency electron beam devices
parametric design The process ofusing general
pa-rameters, rather than individual measures, to automate computer-aided design and drafting (CAD) and
One olthe bigger challenges in telecommunications
is designing antennas and transmissions technologies
that can communicate over vast distances in the
in-clement, radiation-high, temperatllre-flllctllating
en-vironments characteristic 01 space The Cassini
Sat-urn probe shown here in its testing phases, in 1996, is
equipped on top with a parabolic radio antenna
pro-vided by the Italian Space Agency (AS1) [NASAIJPL
image detail.}
parabolic antenna An antenna designed with a
char-acteristic parabolic "dish" shape that captures a
di-rectional beam and focuses it, usually through afeed
short, directional transmission waves, such as
micro-waves, and the diameter of the antenna is designed
to correspond with a multiple of the length of the
wavelength being received Parabolic antennas may
be made from a variety ofmaterials: solid metal, mesh
metal, fiberglass This style of antenna is commonly
used for microwave satellite transmissions, though it
is also used for some long-distance space applications,
such as space probe communications See antenna,
feed hom, microwave antenna, low noise amplifier
reflectorAnantenna, or other reflector, which
uti-lizes the characteristics of the shape of a parabola to
feed horn
parabolic reflector
supporting struts
Trang 2USPTO Patent Resources
IlIet!IlIds ed systems far9JlNlfdal~ dIIIlJ1Slnyetl1l'ltt: IaxtDnj Jay R.(8t!l!n9ham, WA);SDlIt:
(StUmpllll, \VA): saao: DanJ.cetIlin9"1ln, WA) AeJlgnoe:~, -.(8lilllngnut, WA) Aflpl."
oct 3D, tams IilI1L a : 0Il8f 3114 a.nmu.s a.:MI13S1;3M114 t;3GSlI4I8;3G1IIISeRllllaf sa.dl:3I4/l
senZ3" 3R,"·4'
U.S PI1'tn1 DocUlltlllltJ
~tl.,'I84~SoIOf713~OtL 'i8!Sllttsnlct:3MI'!Il'~\I • 1S85L1ylnt"'"
1~7KatoetaI.SlI2/41)(
~~H8tteOtl;OIlYv
.4.U1st11nfbtJt!tltw:HetndOI1,H R.
~,I#gtUJ:I4f'F11I4HlJgtlOC&Multat
A mmOiitotgenerDng aparamtVie doal;n GIl computer wlthoutthe u•• of plogrll\ll'll!ng language A ~
to CflttUtuwltr Cffawlftg1rcmUlftICh oll'ltrdrawtng Of dlfr.rem llimomiont tanl!ton bo syll!he'lJel1 by llIodll1t
CfmWlglntIJttd tsfOaeh dIm_nslllnln "'.m r CItlaWlng 1I#ln9 gl"e" I ~ll vlIllJe,It ial}l\>en a lablll ,",e•• lab
l'lln ~~ etlm ICltlt!htld.rpttYld•• MCSlllljntJont ~jCh ate c.alcuiafOd at d•• tlftltdln adtt~ pl5n WIlf
1\Ill, lIleaY' ua•• ~.,4fI1U.toP'OIItp'~ unribr "~h detlgn vw q IIlCOfporUti Irlt respCll\t, \IIftIl
~ lrda!he ~ plan 1f., JI'Of"e i uncceor a.equfJ't 1111l~ to,clartA1:aan A' adrds1llan WO'lfd do
llItl'P' Iw ltIit."alun 'M1Il dete fnral boll"" 1ffl'9" plan and 1M IMfW' dt1lWlngto cr.e a ~stIod Cl1~
p.lr1%DQ¢ "gn lIle lS•., UlKb thIt col\fl'ollirlg mlgnpI"to bt und lit a n.su OUM nap Acing 4Jlll'!O
The U.S Patent and Trademark Office is
endeavor-ing to make patent and trademark information
avail-able online to the public Patent abstracts,
descrip-tions, and diagrams are currently availablefor recent
patents and images are availablefor historic patents.
Parametric design incorporates a form of expert
sys-tem and is particularly valuable in situations where
many small variations on a basic design (bolts, boxes,
modem covers, PC boards, telephone handsets, etc.)
need to be designed and manufactured In these cases,
a computer program can be used to automate the
de-sign process, by providing guidelines, rather than
single-part measurements, to turn out the many
needed variations thousands of times faster than a
CAD operator could draw each one by hand One of
the early patents for an applied parametric design
computer program was awarded to Synthesis
(OfficeCad), in Washington State, in the 1980s It can
be accessed online, along with other patents filed
since the mid-1970s, on theu.s.Patent and
Trade-mark Office's Web site See CAD, expert system
http://patents.uspto.gov/
parametric equalizerA component device used in
sound systems to selectively manipulate selected
fre-quencies in order to adjust the sound, usually to suit
the taste of the listener
parasiteAnorganism or process which feeds
offan-other without providing a return Intechnology, the
term can refer to a process, or a mechanical or
elec-trical device that monitors or uses transmissions
clan-destinely, or without the usual compensation to the
provider of the transmission Small wiretap devices
are sometimes called parasites, especially ifthey draw
their power from the line being tapped
PARC, Xerox PARCSee Palo Alto Research Center
matching
parity bitA bit which is included in a transmission for error checking or status purposes.In telecommu-nications over a modem, most protocols allow the use
of a parity bit appended to a data stream of a speci-fied length, the parity bit set to zero or one, depend-ing upon the preceddepend-ing data Parity values calculated and stored as the sent bits are checked against parity values calculated from the received bits See parity checking
parity checkingA simple means of checking data integrity after a transmission by comparing the cal-culated value of the parity at the receiving end with the value calculated and stored at the sending end
Parity checking is very commonly used in file trans-fer through modems over phone lines
First the transmitting and receiving ends negotiate a common protocol, for example, ZModem, then the parity setting is selected as odd or even (or none)
Assume a parity setting ofeven for this example Par-ity is calculated prior to sending, by tallying the ones
or zeros in a group of bits (usually seven), and then assigning a parity value ofzeroif there is an even number ofone bits and ofoneif there is an odd num-ber of one bits, (or the converse, by looking at zero bits for odd parity) The sender transmits the data and its associated parity bit The receiver calculates the parity of the received bits and checks to see if there
is a match with the transmitted parity bit Ifnot, there
is a problem
The system is not foolproof; a match does not guar-antee that the data were correctly transmitted, as the parity bit itself may have become altered along with the data, but mechanisms in most software evaluate the frequency ofparity errors so that the user may be alerted and the transmission aborted, restarted from
an earlier point, or resumed later, depending upon the protocol
park driveIn hard drives, "parking" the drive is a means to secure any moving mechanisms that may
be damaged by being jiggled in transit Some hard drives park automatically when not in use, and some use mechanisms to prevent damage ifthe unit is trans-ported (e.g., drives in laptops) Older drives were of-ten equipped with software-parking, and it was quite important to run the software command to park the drive before moving the system or removing the drive
This system is now uncommon Mobile computers are equipped with self-parking drives
park phoneIntelephony, parking is the process of putting a line through to a particular phone so that it can be picked up at another station, or to put a line
on "soft hold" so the conversation can be continued from another phone
park timeoutIn telephony, a time limit on a parked line after which it hangs up the line if the call is not resumed on another line (or the same line)
parking 1.In telephony, parking is the process of putting a line through to a particular phone so that it can be picked up at another station, or putting a line
on "soft hold" so the conversation can be continued
.
• • : • :.: ,
;.~~~,: i:,:i
Trang 3Fiber Optics Illustrated Dictionary
securing a device so that any moving parts that might
be damaged or that might damage other components
are kept in check For example, the read/write head
of a hard disk drive could damage the head and the
magnetic media if it skitters across the drive when it
is moved Parking the drive through software or
built-in electronic sensors ensures that this type of
dam-age doesn't occur Depending upon the operating
sys-tem and type of drive, a drive may have to be
unparked or mounted after it has been parked Older
OSs and drives tend not to be auto-parking It may
be necessary to run a software utility to park the drive
when powering down the system to remove the drive
or to move the computer system 3 In general
con-sumer electronics, the process of tying down,
bolt-ing, or otherwise securing moving parts so they are
not damaged or do not cause damage in transit It is
very common for laserdisc and compact disc players
to have a transit bolt in the back to prevent the trays
from moving around during shipment Always take
care to remove the transit bolt before use, save it by
taping it to the manual or the underside ofthe player,
and always reinsert the same bolt (the length may be
important) before moving the equipment, especially
if it is being shipped by a third party
Parkinson's lawC Northcote Parkinson wrote in the
1950s that work expands to fill the time available for
its completion (For those who are perfectionists, and
believe that if ajob is worth doing, it's worth doing
right, this is doubly true.)
partial response/maximum likelihood PRML
PRML is a means of digitally encoding analog data
and reconstructing it This concept can be applied to
many aspects oftechnology but has been particularly
useful in the development of improved data
broad-casting and storage devices
PRML-technology hard drives, for example, can
pro-vide high disc capacities and faster transfer rates than
earlier technologies based on peak detection (the
de-tection ofvoltage spikes resulting from magnetic flux
reversals) Peak voltages become harder to detect as
data are more densely packed (the peaks become
dif-ficult to distinguish from the noise) To overcome this
problem, anew approach, based on digitally sampling
the analog signal, was developed
Vendors like Seagate have applied a PRML digital
sampling and data reconstruction approach to the
de-velopment ofhigh-capacity drives that use partial
re-sponse (PR) in magnetoresistive (MR) hard drive
heads These heads detect and sample an analog
sig-nal prior to Viterbi detection decoding Together, PR
and MR eliminate overhead in the electronic
equal-ization (undershoot filtering) process, freeing up as
much as an additional storage space Maximum
like-lihood (ML) is used in the conversion ofanalog
wave-forms into digital data Through Viterbi detection, all
possible combinations ofdata are checked for the best
match of least error with the incoming data The
as-sumption is that the least error pattern will most likely
be correct and, in practice, it works quite well
To-gether PR and ML enable faster data transfer rates
through run length limited (RLL) coding and signifi-cant areal density increases over peak detection meth-ods are possible
As PRML technology caught on and was adopted by
a number of vendors, the algorithms and underlying technology were improved to the point where the higher performance versions were called extended partial response/maximum likelihood (EPRML) to reflect further significant improvements over the ear-lier PRML drives See Super DLTtape
partitionSubset, class, section, or division
partition, driveOn hard drives, a usually contigu-ous section of a disk individually initialized and handled by the operating system as a distinct unit Some systems can format the individual partitions in
a variety offormats, Le., a I-Gbyte hard drive with a NeXTStep 400-Mbyte volume on one partition, a 400-Mbyte Linux volume on another, and a 200-Mhyte Macintosh volume on a third, all recognized
by the OS and readable/writable without any unusual technical expertise or demands upon the user
On many microcomputer operating systems, disk volumes and files cannot cross partitions, but many Unix and workstation operating systems can handle volumes that cross partitions transparently to the user, e.g., two 500-Mbyte hard drives used together might appear to the user as a I-Gbyte virtual drive There are many schools ofthought as to whether ahard drive needs to be partitioned A few operating systems can only handle up to four partitions, each with up to 2 Gbytes ofspace and, consequently, a larger hard drive must be sectioned into smaller pieces in order to be handled by the operating system Others don't have this limitation on the number of partitions, and can manage larger-sized partitions In terms ofdisk
rebuild partitions or handle data recovery procedures
if there are several partitions rather than just one Redundant array drives are another way of handling error recovery Often a small 200- to 500-Mbyte par-tition will be set aside as a "swap drive" and not used for other purposes See RAID
partition, memoryIncomputer memory, a !jnked or contiguous section, separate from other sections, that
is allocated for a specific purpose or process, such as video display or frame buffering
party I One of the individuals in a transaction A common legal term used to stipulate an individual or
organizational entity To be party to a transaction is
to listen in or participate In telecommunications, the transaction might be a telephone call, a conversation,
or a computer communication
party lineIn telephony, a line shared by two or more subscribers, so ifone or more subscribers pick up the line and listen when someone else is engaged in the call, they can hear the conversation, and can't make further calls until the current conversation is discon-nected Party lines were very common on older shared phone circuits until the 1960s; they are now uneommon
in North America On ISDN lines and Frame Relay networks, a sort of party line system exists, but is rarely a hindrance to the user, unless too many
Trang 4party line, followingFollowing the party line is a
phrase from politics that indicates acceptance and
promotion of the administration's point of view The
administration might be a political party, a business
entity, or other institution It is sometimes used as a
derogatory phrase for ambitious compliance, or for a
person who doesn't think for him- or herself, but
pro-motes the current popular point of view
PAS 1 see profile alignment system 2 See Priority
Access Service
pascalAnSI unit ofpressure equal to one newton per
square meter
PascalA programming language descended from
ALGOL, developed by Niklaus Wirth in 1970
Pas-cal became especially popular in the 1980s for
teach-ing programmteach-ing concepts and techniques A
struc-tured, typed language, Pascal is somewhat similar to
Modula IT, and fits somewhere between C and higher
cryptic than C, but also less preferred by
program-mers in commercial development environments, yet
is generally preferred over the less structured BASIC
in educational environments See Modula IT, C
Pascal, Blaise(1623-1662) Atalented French
inven-tor and mathematician, Pascal devised one ofthe
ear-liest calculators, a "Pascaline," while still in his teens
It was a numerical base ten, movable dial, wheel
cal-culator designed to assist his father in carrying out
his duties as a tax collector Pascal appears to have
come up with the design independently, and probably
was not aware of the earlier calculator developed by
Schickard at about the time of Pascal's birth Pascal
also did research in fluid dynamics See Schickard,
Wilhelm
pass throughv To move through a component
de-vice or leg of a network without significantly
alter-ing the characteristics of that which has just been
passed through, or without being altered by that which
is passed through See passthrough device, tunneling
passband1 The range of transmission frequencies
that can pass through a filter without a significant
de-crease in amplitude (attenuation) A passband filter
allows selective screening out ofirrelevant or
undes-ired frequencies in order to create a device for a
spe-cific purpose, or to simplify its operation 2 A signal
that loses no spectral energy at direct currents (DC),
unlike a baseband signal AManchester-encoded
sig-nal is one example of a passband sigsig-nal
passthrough device1 Adevice chained between two
other devices, which passes data through without
changing them For example, an external memory
module might be attached to a computer, with an
ex-ternal hard drive attached to the memory module The
memory module passes through the hard drive
sig-nals in such a way that the hard drive works just as
though it were directly attached to the computer See
daisy chain 2 A device that provides access to and
passes back the signals transmitted by another
Some-times used as a diagnostic tool
passwordA word or combination of characters
which, when provided by a person or entity wishing
against certain characteristics, or a list of those who are authorized to have access If a match is found, entry is permitted Password protection systems are
unwise to tape passwords to monitors or desks where
com-mon words as passwords; a moderately long password with a combination ofletters and symbols is safer See anonymous FTP, back door, back porch
patchv To connect one circuit with another, usually through an intermediate line For example, on old
tele-phone switchboards, the operator would patch
through a call by taking ajack connected at the other end to the main switchboard, and plugging it into the phone receptacle for the individual getting the call Apatch is a temporary connection, one subject to fre-quent change or used for diagnostic purposes
patch, softwaren.In software, a patch is a piece of code that is inserted into the original code to over-ride some of the original programming, or to add ca-pabilities or data which weren't in the original code and perhaps should have been A patch is distin-guished from an upgrade in that it typically is intended
to correct oversights or errors, whereas an upgrade is usually of greater scope, intended to enhance or ex-tend the capabilities of the program In many prod-ucts, the two are combined
patch, soundIn electronic music, a sampled segment
of sound stored digitally The sound is measured and
or-der to create a digital impression ofthe analog sound wave For the most part, the more frequent the sam-pling, up to the limits ofhuman perception, the more true to the original the sample tends to sound (the ca-pabilities of the playback mechanism contribute as well) Sound patches can be generated by and used with many commercial sound synthesizers and com-puter synthesizer software MIDI is a common pro-tocol used in the music industry for communicating digitized sound between MIDI-compatible instru-ments and software programs Speech and music sound patches are often used to enhance multimedia CD-ROM educational and entertainment products More recently, messages composed from speech patches are becoming common on the Web See quan-tize, sampling
patch bay, patch boardA hardware panel designed with multiple connecting ports such that the configu-ration ofthe patched in cables can be readily changed
In other words, it is set up so that temporary circuits,
or those which are frequently changed, can easily be rewired Dishwasher-sized patch bays are often equipped with wheels so they can be moved in or out
of a work area, and usually have receptacles or ter-minals for easy insertion and removal ofpatch cords and/or wires Patch boards are useful for prototyping, monitoring, and testing new circuit layouts See patch panel
patch cordA short length of wire or cable used to connect circuits The connectors at either end vary, but are often RCA jacks or BNC connectors Patch
Trang 5Fiber Optics Illustrated Dictionary
cords are commonly used with patch bays, patch
pan-els, and electronics components Videographers and
musicians often refer to video and audio connecting
cables as patch cords, since video equipment
connec-tions are frequently reconfigured
patch panelAhardware device, often wall-mounted,
that facilitates the connection and reconfiguration of
temporary circuits Patch panels are often mounted
casual passersby, such as in maintenance closets A
patch panel may resemble a distribution frame, in that
it has a grid ofopenings or connectors through which
circuits can be routed It commonly has mounted
re-ceptacles to match the types ofjacks used in that
par-ticular circuit
Fiber optic patch panels are typically made with
greater precision and strain relief assemblies than
CAT-5 Ethernet panels, for example, because the
in-tegrity of the coupling in fiber optic connections is
crucial to its effectiveness
Patch Panel- Fiber Optic
Patch panelsfaCilitate the coupling and quick
reor-ganization ofwire orfiber optic connections The
pan-els are commonly installed on walls or in wiring
the connectors This panel illustrates banks of
com-mon SC- (top) and ST- fiber optic connecting ports.
Connectors may have locking mechanisms with
align-ment slots and knobs (e.g.• bayonet mounts) to
pre-vent accidental disconnection
Depending upon the type ofpanel and connectors.
the panel may be passive linking the connections
straight across, or active, with electronics built in to
the panel to influence the signals (e.g.• providing
am-plification).
Patel,C.KumarN (1938- )AnIndian-born
Ameri-can physicist with an interest in optics, especially
molecular spectroscopy and laser systems Patel
stud-ied in India and at Stanford University, then began
his career at Bell Labs in 1961 where he became
Executive Director of Research, Materials Science,
Engineering and Academic Affairs, a position he held
until 1993 He then served as Vice Chancellor
of Pranalvtica
Patel holds over 30 patents and has received many
honors, including the OSA Lomb Medal and the
Na-tional Medal of Science (1996) for the invention of
in-strumental in the development of the Raman laser, a tunable laser demonstrated in 1969
Patel has continued to actively pursue applications of lasers In June 1997 he and his colleagues submitted
a patent application for an optical bit rate converter suitable for time division multiplexed (TOM) multiaccess communications networks See Javan, Ali
patentAregistration process fonnally established in the United States in April 1790 which provides a record of the ownership, development, and date and method ofcreation ofunique products and processes The first American patent was granted on 31 July
1790 By 1802, applications had increased to the point where a separate Patent Office was set up, and more rigorous scrutiny was established by 1836
stored in a central government repository that is open
to the public and intended to further technological progress by the encouragement of the dissemination
of ideas Japanese patents have been available over networks for some time now, and recent U.S patents are now searchable on the Web through the U.S Patent and Trademark Office site The Clinton Ad-ministration announced on June 25, 1998 that over
20 million pages of patent and trademark infonna-tion would be provided free to the public on the In-ternet by year's end Content is supplied through the Commerce Department's large database of text and images The collection will include the full text of 2 million patents dating from 1976, 800,000 trademarks and 300,000 pending registrations dating from the 1800s Tiff images are available for historic patents Patent applications must follow very specific fonnat and content guidelines laid out by the patent office Patent registration grants exclusive intellectual and certain commercialization protections to the inven-tor for a tenn of 17 years in the U.S (international
the same idea simultaneously or previously, without knowledge that the idea has been patented, preference for the idea now goes to the inventor who first is granted the patent This is a change from historical procedures in which an earlier inventor, if she or he had documents to prove the case, could have a patent from a later inventor overturned
Many people incorrectly assume that the patent pro-cess exists to explicitly prevent others from infring-ing on patents, but it is the responsibility ofthe patent owners, not the patent office, to police the use and abuse of patented ideas The patent does, however, defme the nature and extent of the legal protection available to the inventor through the justice system Granting of a patent does not include granting of a right to manufacture a product incorporating the idea, since other patents for other aspects of the invention may exist
The most important aspect of the patent and the
in which the inventor lays out, in point form, the
Trang 6tiqued and rejected or returned to the applicant for
revisions Since uniqueness is often evaluated in a
historical context in the Prior Art section, historical
antecedents and current similar inventions must be
described by the applicant thoroughly and succinctly
The invention must also be more than a half-baked
idea, since the patent application must include a clear
description of how to build or otherwise recreate the
invention itself, without undue difficulty to a
layper-son or someone appropriately skilled in the area of
specialization appropriate to a specialized invention
Hardware patents usually fall under the products
egory and software patents under the process
cat-egory Note that patents, copyrights, and other legal
registration procedures may grant ownership to the
employerof the inventor rather than the inventor, if
the employee undertook the invention in the course
of his or her normal work hours or duties
One of the most famous patent clerks in history was
Albert Einstein, who worked as a junior clerk in the
Swiss Patent Office when unable to find work as a
teacher or research scientist While working there, he
wrote some ofhis most startling, insightful treatises
on relativity See copyright, trademark
http://www.uspto.gov/
Paterson, TimPaterson developed a simple but
his-torically important disk operating system for Seattle
Computer Products in the late 1970s The product was
which was the most successful and well known at the
time, with over halfa million copies distributed
Pater-son created a basic operating system called QDOS
(Quick and Dirty Operating System) which he has
stated was derived in part from the program interface
described in a CPM manual from the mid-1970s
Microsoft bought it, fIXed it up a little, and provided
it to ffiM soon after ffiM released it initially as PC
DOS 1.0 Meanwhile, Seattle Computer Products
re-tained the rights to QDOS Microsoft subsequently
bought out all QDOS distribution rights for $50,000
The Microsoft financial empire essentially sprung
from this transaction as the product was developed
into MS-DOS and, eventually, after many facelifts
and enhancements, evolved into Windows See
Digi-tal Research; Kildall, Gary; Microsoft Corporation
conduit, or other end-to-end, hop-to-hop, or
as-you-go means of delineating the track followed by a
per-son, process, transmission, or data unit while
travel-ing from one point, node, or endpoint to another A
file path is one which indicates the hierarchical
orga-nization and location ofa specific file or grouping of
files A transmissions path is the specific or general
direction of radiant energy travel
path information unitPIU In packet networking, a
message unit consisting of a transmission header
(TM) or a transmission header combined with a
fol-lowing basic information unit (BIU) or segment See
datagram
Path Terminating ElementSee SONET path
termi-nating element
ofcomparing text, symbols, images, or other elements
to determine whether they are the same, similar, or mathematically equal The process ofpattern match-ing is widely used in database search and analysis mechanisms, and its cousin, pattern recognition, is common to artificial intelligence applications includ-ing expert systems, robotics, and others
Pattern recognition was in its infancy in the late 1950s and early 1960s, when computing systems were ex-pensive, cumbersome, and programmed with punch cards Nevertheless, early researchers at the time, sensing its potential, developed equipment and algo-rithms which could read a few handwritten letters, if they were plainly written See Perceptrons
pay phone, pay telephoneSee payphone
payloadThe user information, and sometimes ac-counting and network administration information, carried in the upper layers in a layered architecture, within a cell, frame, packet, or other network data transmission unit Separate from but associated with the payload, there is frequently signaling, header, er-ror checking, and other data which relate more to the type and manner oftransmission than to the informa-tion content from the user or process sending the transmission
Payload Data SegmentPDS In communications satellites, the data services that are made available to authorized users See Unified User Interface
Payment Extension ProtocolPEP An HTTP pay-ment extension protocol described by the JEPI project
in August 1996 in conjunction with seven examples ofthe Universal Payment Preamble (UPP) that could
be used over PEP The purpose of the system was to develop a practical, automatable payment system for running over the widely distributed HTTP applica-tions on the Web PEP enables UPP to be embedded
in HTTP to support Web client/server payment trans-actions Examples of basic payment mechanisms in-clude queries to determine what types of payment forms are supported, presentation ofpayment options, demand payment options, payment acceptance/rejec-tion, and payment option queries See e-commerce, JEPI, Universal Payment Preamble
payphone, paystation phoneAny self-contained public or private telephone unit that requires a per-call or per-minute fee, usually directly transacted with the phone Although some human-operated stations exist most require payment by coin or stripe card The first pay telephones were attended by operators who collected the fees for the calls One of the early coin box patents was issued in 1885, and William Gray installed a public coin phone in Connecticut in
payphone postpayPayphone calls paid after comple-tion, usually with a calling card or credit card
payphone, privateAlso known as COCOT, this is a customer-owned coin-operated phone, as might be found in a hotel lobby or tavern COCOTs may pro-vide only limited access to long-distance carriers PBX Private Branch Exchange See Private Auto-matic Branch Exchange
Trang 7Fiber Optics Illustrated Dictionary
to refer specifically to IBM and third-party licensed
hardware, in fact, PC correctly refers not only to Intell
IBM computers, but also to any personal computer
or microcomputer priced in a consumer or small
busi-ness price range 2 printed circuit See printed
cir-cuit board 3 program counter 4 protocol control
PC cardSee PCMCIA card
PC, IBM/Intel colloq. In general and marketing
terms, PC is understood as a subset ofpersonal
com-puters, consisting of Intel-based IBM hardware, or
third-party licensed hardware, running the IBM OS/2
software or, more commonly, running the Microsoft
Windows graphical operating environment in
con-junction with MS-DOS For information on specific
IBM desktop computers, see the listings under IBM
Personal Computers
communications system, a point on a segment of the
orbit or ground track when the satellite is closest to a
specific ground station 2 Premises Cabling
Associa-tion 3 protective connecting arrangement
Commer-cial connecting rental agreement, required by AT&T/
Bell prior to divestiture for telecommunications
de-vices that were not AT&T/Bell, were connected to the
AT&T!Bell system See Carterfone decision
3 process control block 4 See printed circuit board
5 protocol control block (in TCP and similar network
protocols)
Association
Control Information
Associa-tion Fonnerly known as Telocator, PCIA is a national
association representing the mobile communications
industry
code modulation
PCMCIAPersonal Computer Memory Card
Inter-face Association Aprofessional association of
elec-tronics peripherals and semiconductor manufacturers
and software engineers See PCMCIA card, PCMCIA
standards
PCMCIA card, PC cardA standardized computer
peripheral card fonnat, not much bigger than a fat
wallet card, which is commonly used in portable
com-puting applications PCMCIA cards (since the
mid-1990s called PC cards because it's easier to say) are
microminiaturized devices with a thin edge
connec-tor, including memory cards, hard drive cards, fax/
modem cards, network interface hookups, and more
They are used in radio phones, laptop and palmtop
computers, digital cameras and camcorders, and
vari-ous other portable electronic devices The most
com-mon cards are called Type I or Type II (Type III is
less common, and Type IV is vendor-specific) Most
laptop peripherals use Type II cards, and it pays to
Hard drives and radio devices tend to use the thicker Type III cards
PCMCIA standards A set of 8-bit bus standards which bears the same name as the organization which developed the standards, the Personal Computer Memory Card Interface Association PCMCIA stan-dards were developed and tested in the late 1980s and released for general use in 1991 While there is fairly good adherence to the standards, compatibility is not
them, or to get them with a good return policy The set ofstandards includes Type I, Type II, Type III, and Type IV See PCMCIA card
PCMIAPersonal Computer Manufacturer Interface Adaptor
Pri-vate Carrier Paging
re-writable 3 problem/change report 4 See processor configuration register 5 See Program Clock Refer-ence
per-sonal communications software
PD See phase drive
PDA See PDA microbrowser, PDA macrobrowser, Personal Digital Assistant
Web-Compatible PDA Macrobrowser
A full color, graphics-capable Palm personal digi-tal assistant (PDA) connected via radio link to the Internet and installed with the SojtSource/Catarra HTML-compatible macrobrowser client, which pro-vides the full-featured Web surfing ofa desktop com-puter, with a pen to scroll, click, enlarge, or cany out other typical browser actions This fully HTML-com-patible combination of hardware and software has many advantages over more limited microbrowsers and WAP technologies, including the convenience of accessing standard Web pages and security features rather than requiring special software designed for WAP-based devices WAP is appropriate for limited resource devices, but for full Web browsing, the SojtSource/Catarra server/client combination is cur-rently the only product that provides unrestricted graphical Web-surfing on PDA mobile devices.
Trang 8ing full Web compatibility on limited-resource
por-table devices through quick conversion and display
algorithms transparent to users, Web page designers,
and security providers Macrobrowsers include
dis-play software technology installed on a Personal
Digi-tal Assistant (PDA) working in conjunction with a
proxy server Thus, unlike microbrowsers,
informa-tion providers don't have to maintain two sets ofWeb
pages or a separate type ofdigital certificate - a
mac-robrowser supports the existing Web infrastructure
Macrobrowsers began appearing in 2001 as PDAs
with better memory and display technologies were
re-leased They will likely co-exist with microbrowsers
for a while, but may supersede them due to the
im-proving power and resolution of handheld wireless
devices and the relative ease of implementing Web
pages and security features compatible with
macro-browser-enabled devices See PDA microbrowser,
SoftSource, Wireless Application Protocol
PDAmicrobrowserAsoftware application designed
to provide limited Web access compatibility for
con-strained-resource devices Microbrowsers began to
imple-ment limited-set, proprietary, or specialized
adapta-tions of current Web browsing languages to run
ef-fectively on Personal Digital Assistant (PDA) devices
with limited memory and display resolutions The
most common strategy for microbrowsers is to run a
Web proxy gateway and to adapt Web pages to the
limited-set languages compatible with these devices,
through simplified/specialized markup languages
Microbrowsers are a reasonable way to support
con-strained-environment handheld computing devices,
but put an extra burden of time and expense on Web
page designers, programmers, and security providers,
as two sets ofWeb pages and digital certificates must
be maintained if microbrowsers and regular HTML
browsers are to be supported on the same Web site
Microbrowsers will remain viable for a while for
lim-ited-resource devices but may eventually be
super-seded by PDA macrobrowsers for general purpose
browsing, as handheld devices become more
power-ful and feature-rich See CHTML, PDA
macrobrow-ser, Personal Digital Assistant, WAP Forum
PDC See Personal Digital Cellular
PDF See Portal Document Format
PDL See page description language
PDP 1 See plasma display panel 2 See power
dis-tribution panel
PDP- A series of Digital Equipment Corporation
(DEC) Programmed Data Processors (PDPs) that
power-ful, smaller-scale, lower-cost computers The PDP-l
sold for only a tenth of the price of many computer
behemoth mainframes This made the PDP-line
mar-ketable to educational institutions and businesses that
couldn't afford million-dollar computing systems and
they became very popular with computer science
stu-dents, with many user (and hacker) groups springing
up around the machines
in 1960 and a PDP-3 was built by a DEC client The PDP-4 and PDP-5 followed in 1962 and 1963 and DEC released about one a year from then on By the mid-1960s, DEC had launched a desktop model of the PDP-8 To be useful, it needed lots ofperipherals, and its price was far beyond the range of personal computer owners, but for under $20,000, it was a tran-sitional machine to the smaller scale mini- and, even-tually, desktop computers of the late 1970s and be-yond By the early 1970s, the series was up to the PDP-16, but many purchasers were still using PDP-8, PDP-I0, and PDP-II machines into the 1980s The
PDP-x series was gradually superseded by DEC's
VAX computers in the mid-1980s, but hobbyists still like to pick up the PDP-x computers at auctions and computer salvages See VAX
PDS See Payload Data Segment
PDU See Protocol Data Unit
PDUS Primary Data User Station The combination
of a ground station and a satellite image processing system
peak cell ratePCR In ATM networking, a traffic flow measure that describes the upper cell rate limit, which may not be exceeded by the sender See cell rate
peer entitiesInlayer-oriented network models, en-tities within the same layer, usually diagramed and visualized as horizontally related
peer modelA networking model built with the
internetwork layer routing can be exchanged See in-tegrated model
peeringThe voluntary exchange of routing an-nouncements in order to effectively establish data paths among providers
access See cable access
Pender, John(ca 1860-1896) A British merchant who succeeded in establishing ambitious historic tele-graph cable links between Western Europe and the Far East and Australia In 1856, John Pender became
a director in the Atlantic Telegraph Company and thus was involved in the first transatlantic cable enterprise spearheaded by Cyrus W Field Pender's subsequent ventures indicate that he was inspired by the success
of the Atlantic telegraph cable installation and its fu-ture economic impact
Wanting to get in on the ground floor of the new in-dustry, in 1864, Pender formed the Telegraph Con-struction and Maintenance Company (Telcon), fore-seeing the future need for cable manufacture and maintenance Not satisfied with this alone, however,
he then founded the British Indian Submarine Tele-graph Company, in 1869, with the goal of linking Britain and India For building the local Falmouth link, Pender formed the Falmouth-Gibralter-Malta Telegraph Company but soon changed it to the more generic Eastern Telegraph Company as plans and
Trang 9Fiber Optics Illustrated Dictionary
locations changed as the project advanced and the port
location was changed to Porthcurnow (later
Porthcurno - PK)
By 1879 Pender was not only a significant
telecom-munications magnate, but had realized the
remark-able feat of building a telegraph cremark-able link between
London, England, and Bombay, India
In 1882, Douro mail steamer and passenger ship sank
offCape Finisterre following a collision with a
Span-ish steamer The John Pender telegraph ship, part of
Eastern Telegraph's fleet, was nearby and took off a
number of passengers, providing them with basic
needs and enabling them to telegraph their loved ones
with reassurances See Field, Cyrus West; Porthcurno
penetration Gaining access to a system, circuit,
fa-cility, or operation, usually for security reasons or
unlawful access Physical penetration of circuits or
networks can be done through means oftaps or black
boxes Logical penetration can be done through
pass-word-guessing, Trojan horses, viruses, and back
doors Bodily penetration can be done through
over-riding electronic security measures, entering as an
impostor, or using insider privileged access in an
un-ethical manner See back door, Trojan horse
penetration tap I Any means by which a conductor
is accessed by piercing the outer layers of shielding
and grounding and connecting to the current circuit,
with the intention ofnot disrupting current
transmis-sions 2 A network connection technique which
en-ables devices to be attached to the network cable
with-out interrupting current network operation The tap
is carried out with a sharp tool which can pierce the
outer and inner ground shielding ofthe network cable,
such as a coaxial cable commonly used in Ethernet
implementations
penetration testing Testing a system for the
integ-rity of its secuinteg-rity This is sometimes done by
inter-nal staff, contractors installing the security measures,
or outside experts hired totryto penetrate the
sys-tem In the telephone and computing worlds, known
"hackers" are sometimes hired totryto penetrate a
system to try to identify security holes before the
sys-tem is opened up to employees or the public,
depend-ing upon its nature In 1998 it was found that cash
cards, which were generally considered reasonably
safe from decryption and unauthorized use, could be
penetrated by measuring their electrical emanations
and properties, a finding that calls into question the
use ofcash cards in place of traditional means of
cur-rency exchange
PentiumAnIntel Corporation 80586-based central
processing unit (CPU), designed to succeed the
80486, introduced in 1993 Originally released at 66
MHz clock speed, other versions came out,
includ-ing a 100 MHz version with a l6-bit cache and a
64-bit memory interface, and eight 32-64-bit
general-pur-pose processing registers The name is derived from
the "5" in the processor line 80x86 due to a court
rul-ing that a number cannot be trademarked
Pentium IIAnIntel Corporation central processing
unit (CPU) similar to the Pentium Pro Unlike the
Pentium Pro, which incorporates the level 2 (L2)
cache into the chip with the CPU, the Pentium II op-erates with a cache inserted in a slot on the mother-board, thereby increasing the amount of time it takes for the two to communicate Italso incorporates MMX circuitry intended to improve graphics and multimedia-related operations
Pentium MMX Pentium Multimedia Extension,
Pen-tium Matrix Math Extension The MMX is essentially
a Pentium Pro chip enhanced with a number of new data types and floating point instructions that enhance computing-intensive operations such as graphics Applications are becoming increasingly visual in na-ture, with more graphical user interfaces, image pro-cessing, rendering and raytracing, videoconferencing, realtime games, and virtual reality applications, so support for commonly executed graphics and math-intensive computing processes on the chip is intended
to support these growing areas of interest Also, by incorporating capabilities similar to those supplied by direct memory access (DSP), Intel can reduce its re-liance on the DSP technologies of other vendors The Pentium MMX incorporates what Intel calls Single Instruction, Multiple Data (SIMD) techniques
to allow several processes to be carried out with a single instruction See Pentium II, reduced instruc-tion set computing
Pentium Pro, P6AnIntel Corporation 80686 cen-tral processing unit (CPU) in the Pentium brand name line, introduced in 1995 as a successor to the Pentium processor The Pentium Pro originally shipped as a 133-MHz CPU and shares a number of commonali-ties with the Pentium, including a 64-bit memory in-terface It is a two-part chip in the sense that it has a CPU and a level I memory cache, plus a level 2 (L2) memory cache layered into the CPU rather than re-siding separately on the motherboard It is a hybrid chip with an underlying RISC structure, but also in-cludes a CISC-RISC translator for downward com-patibility The clock speed of the first version was 133-MHz, with other versions following
People's Communication Charter A global
move-ment by a number of international communications associations to demand the protection of the quality ofcommunication services, their accessibility, afford-ability, and ease ofuse by the public in order to safe-guard basic human rights The Charter grew out of concerns about new and existing communication technologies conscripted around the world by self-interested governments or allocated preferentially to private parties for use as conduits for information delivery for propaganda or for-profit ventures, at the expense of communications supporting education, community needs, and civil rights See Milan Decla-ration on Communication and Human Rights http://www.waag.org/pcc
PEP I Packetized Ensemble Protocol Ahigh-speed,
proprietary, full duplex transmission protocol from Telebit It has error-correcting mechanisms and is said
to handle line noise well; it is no longer in general use 2 See Payment Extension Protocol 3 See Pub-lic Exchange Point
PER See Packed Encoding Rules.
Trang 10munications usage by time PLU is a ratio of the
lo-cal minutes to the sum of lolo-cal and intraLATA
long-distance minutes between exchange carriers, sent over
Local Interconnection Trunks Switched access and
transiting calls are not included
PerceptronsSelf-organizing, pattern recognition
sys-tems built in the early 1960s at Cornell University
These systems were rudimentary, barely managing to
recognize simple letters, yet studies and experiments
of this kind led to the optical character recognition
and handwriting recognition systems we now take for
granted
At the same time, at the Massachusetts Institute of
Technology (MIT), researchers were developing
pat-tern-matching systems for medical diagnosis, with a
system designed to screen for cancer cells through a
microscope See neural networks, pattern matching
perforator Atool to make a hole, to penetrate a
sub-stance, to punch an opening Common three-hole
punches are perforators Electronic perforators are
widely used to turn electronic signals into code
pat-tern holes in punch cards and paper tapes See chad,
Hollerith card, punch card
performance categorySee category ofperformance
perigeeThe point in an orbit nearest the gravitational
center of the body being orbited See apogee,
periapsis
The perigee is the closestpoint ofan orbiting object
to the body being orbited.
period1 Cycle, interval of time, portion oftime
en-compassing a distinct culture (historical period) 2
Geologic time division that is part ofan era and longer
than an epoch 3 The time interval between two
con-secutive orbits of a satellite through a specific point
(usually the perigee) in the orbit 4 In electronics,
one interval of a regular, repeating event
Peripheral Component Interconnect, Peripheral
Connect InterfacePCI A very popular local bus
standard developed by Intel in the early 1990s to
sup-port 32/64 bit data that was compatible with the new
Pentium processors coming out at the time It was
designed with a newer chipset, to improve on the ISAs
and VLBs that were then common, and to include bus
mastering (use of the system bus) Since PCl's
de-velopment, PCI slots have become common in Apple
Macintosh and Intel-based mM-licensed machines,
along with upgraded versions of the VESA VL bus
The PCI Mezzanine Card (IEEE P1386.1) was
de-signed to work with the PCI specification
not a main component of a system, but which, when connected to that system, enhances its functionality, speed, or storage capabilities Peripheral devices gen-erally cannot perfonn useful functions unless con-nected to the main system Monitors, 'speakers, key-boards, scanners, video cameras, and printers are ex-amples ofperipheral devices CD-ROM drives are an exception in that some are now designed to play au-dio CDs even if not connected to a computer 2.In the telephone industry peripherals may also be called outboard processors, applications processors, or ad-junct processors
PerlPractical extraction and reporting language A powerful, flexible, general-purpose, interpreted
scriptin~language (originally spelled with a lower-case "p' ) developed by Larry Wall in 1986, and now extensively used for platform-independent scripting
on multiple platforms on the Internet The syntacti-cal structure ofPerl is quite remarkable (perhaps ow-ing to Larry Wall's expertise as a low-inguist); useful, powerful routines can be written in a few lines or sometimes even in a few characters.Animportant tool for shell scripting, Common Gateway Interface (CGn development, and much more When combined with Penguin, it may be a serious contender with Java for object-oriented, Web-related interface design and Automation The Perl Journal gives practical assis-tance to Perl programmers
Permanent Number PortabilityPNP A way for a
::~~n:~j~~tit~f:;~~~~~:~e~:~~n~~:;~~ •
to a different service provider in the same locality permanent virtual connection, permanent virtual circuit PVC A logical communications channel (which may differ from the physical topology over which it is laid) established to stay the same for some time In an ATM environment, there are two types of PVCs: permanent virtual path connections (PVPCs) and permanent virtual channel connections (PVCCs) PVCs provide manually configured connections be-tween end systems The addressing information, Vir-tual Path IdentifierNirVir-tual Channel Identifier (VPI/ VCI), must be put into both devices for connectivity
2 In Frame Relay networks, a PVC is a logical link, with network management-defined endpoints and Class of Service (CoS) The link consists of an origi-nating element address, data link control identifier, terminating element address, and termination data
linkcontrol identifier See RFC 1577
permeability The porosity or penetrability of a sub-stance The degree to which liquids or gases can pass through a substance Contrast with reluctance
permeability, magneticThe property ofa magnetiz-able material that determines the degree to which it will modify the magnetic flux in a region it occupies within a magnetic field See magnetic field
persistence 1.Perseverance, endurance, running the course, keeping on or with, tending to continue (A quality essential to writing a reference ofthis magni-tude, since documenting the telecommunications industry is like trying to gas up a car that's driving