-Encyclope.dia
`·
`of ··
`·
`Electronics
`
`2nd Edition
`
`1
`
`Navico Ex. 1019
`
`

`

`.,.....
`
`Encyclop~dia
`of ·
`Electronics
`
`2nd Edition
`Stan Gibilisco
`Neil Sclater
`Co-Editors-in·Chief
`
`®
`TAB Professional and Reference Books
`
`Division of TAB BOOKS
`
`Blue Ridge Summit, PA
`
`2
`
`

`

`SECOND EDITION
`THIRD PRINTING
`
`© 1990 by McGraw-Hill, Inc.
`
`Printed in the United States of America. All rights reserved. The publisher
`takes no responsibility for the use of any of the materials or methods
`described in this book, nor for the products thereof.
`
`Library of Congress Cataloglng-in-Publlcation Data
`Encyclopedia of electronics I by Stan Gibilisco and Neil Sclater.
`p.
`cm.
`ISBN 0-8306-3389-8
`I. Electronics- Dictionaries.
`TK7804.E47 1990
`621 .38 1 '03-dc20
`
`I. Sclater, Neil.
`
`89-77660
`CIP
`
`For information about other McGraw-Hill materials, call
`1-800-2-MCGRAW in the U.S. In other countries call your nearest
`McGraw-Hill office.
`
`Vice President & Editorial Director: Larry Hager
`Technical Editor: B.J. Peterson
`Director of Production: Katherine G. Brown
`Book Design: Jaclyn J. Boone
`Cover Design: Lori E. Schlosser
`
`l .
`
`3
`
`

`

`-
`
`Contents
`
`Editorial Review Board
`Preface
`Schematic Symbols
`A Absolute Temperature Scale-Azimuth Resolution
`B Back Bias-Byte
`c Cable-Czochralski Crystal-Growth System
`D Daisy-Wheel Printer-Dynode
`E Earphone-Extrinsic Semiconductor
`F Facsimile-Fuse
`G Gage-Grid-Dip Meter
`H Hairpin Match-Hysteresis Loss
`I
`IC-ITU
`J Jacket-Junction Transistor
`K Karnaugh Map-Kooman Antenna
`L Labyrinth Speaker-Lux
`M Machine Language-Mylar Capacitor
`N NAND Gate-Nyquist Theorem
`0 Octal Number System-. Oxygen
`p Pacemaker-Pythagorean Theorem
`Q Q Factor-Quartz
`R Rad-Rutherford Atom
`s Safety Factor- Synchro System .
`T T-1 Carrier-Two-Track Recording
`u UHF-Universal Receiver-Transmitter
`v Vacuum-Tube Voltmeter-VXO
`w Wafer- Wye Match
`x X-Axis-X-Ray Tube
`Y . Yagi Antenna-Yoke
`z Zener Diode-Zero Bias
`
`Index
`
`vii
`ix
`xi
`
`I
`83
`129
`251
`327
`367
`411
`431
`451
`487
`491
`499
`533
`575
`593
`621
`685
`689
`737
`833
`881
`887
`911
`921
`923
`925
`927
`
`4
`
`

`

`TRADEMARKS
`
`Algon qui~ Industries, Inc.
`
`Apple Computer, Inc.
`
`Control Data Corp.
`
`Digital Equipment Corp.
`
`Driver Harris Co.
`
`Algon®
`Apple IP"
`lie™
`lie TM
`II PlusT•
`Cyber™
`Cray X-MP™ Cray Research, Inc.
`DEC™
`PDP™
`UnibusT•
`NichromeT•
`Hypalor®
`Kevlar®
`Mylar®
`Teflon™
`Tefzel™
`Alume1T"
`Chrome!'"
`MultibusT•
`IBM™
`IBM PC™
`PCAT™
`PC XT™
`HEXFET"'
`Moog ®
`TMOS™
`VMEbusT•
`
`E.I. DuPont de Nemours and Co., Inc.
`
`Hoskins Manufacturing Co.
`
`Intel Corporation
`
`International Business Machines Corp.
`
`International Rectifier, Semiconductor Div.
`
`Moog Inc .. Industrial Div.
`
`Mot orola Semiconductor Product s Sector.
`
`Teletype®
`T elex™
`Remington
`Rand Tl•
`Ethernet ®
`Xerox®
`
`Telet ype Corporation
`
`Telex Communications, Inc.
`
`Unisys Corp.
`
`X erox Corp.
`
`5
`
`

`

`Editorial
`Review Board
`
`Dr. Benjamin M. Dawson
`Dept. of Brain and Cognitive Sciences
`Massachusetts Institute of Technology
`
`Dr. Ivan Flores
`Professor of Statistics and Computer
`Information Sciences
`Baruch College of the City
`University of New York
`
`Mr. Richard Geddes
`Princeton Gamma-Tech
`
`Dr. Ronald Gepner, P.E.
`Mercer Community College
`
`Mr. Stephen W. Hinch
`Hewlett Packard
`
`Mr. Lewis Meixler, P.E.
`Plasma Physics Laboratory
`Princeton University
`Dr. Kevin J. Scoles
`Dept.of Electrical and Computer Engineering
`Drexel University
`
`Mr. Roger G. Stewart
`David Sarnoff Research Laboratories
`
`Mr. jim Wilson
`Director of Education
`Texas Educational Corporation
`
`6
`
`

`

`Preface ·
`
`The Encyclopedia of Electronics-2nd Edition is mtended as a general reference in the
`rapidly expanding field of electronics. Where so comprehensive a subject as
`electronics is concerned it is inevitable that there should be an overlap with physics,
`mathematics, chemistry, and computer science. The introduction of new concepts
`and products into the field is being reflected in the language. Electronics-related
`words, phrases, acronyms, jargon, and even "buzz" words have kept pace with
`technology over the past five years, since the publication of the first edition.
`Many words and phrases have migrated from the more forbidding lexicon of
`pure and applied science. People with little or no formal educatfon in science and
`technology now regularly discuss products and concepts in terms that were heard
`only in the laboratory or seen only in professional journals a few years ago.
`High-technology terminology is entering the mainstream through the popular
`media-television, radio, newspapers, and general interest magazines. Some com(cid:173)
`prehension of advanced technology is needed to make sense of the copy in the ads
`for the latest TVs, VCRs, stereo systems, automobiles, and appliances--to say
`nothing of personal computers, cordless telephones, and facsimile machines.
`Even those who profess to have no special interest in science and technology are
`now surrounded by products that contain such recent examples of high technology
`as LEDs, liquid crystals, integrated circuits, and microcontrollers. Products range
`from watches, calculators, and cameras to TV sets, stereos, VCRs, and microwave
`ovens. Traditional home appliances from telephones to washing machines _have
`been improved with electronics. Many games and toys are now sophisticated
`electronics products. There may not be a personal computer in every home, but the
`numbers are rising.
`Outside the home the impact of electronics is also conspicuous. Automobiles are
`now packed with 'electronic controls, safety devices, and entertainment products.
`The banks have computer-based automated tellers; service stations have computer(cid:173)
`based test equipment; and the instruments and apparatus at the doctor's office have
`been updated with electronics. The new technology has been absorbed by business,
`industry, telecommunications, aviation, and even recreational boating. However,
`the most significant trend discernible over the past five years has been the ongoing
`merger between computers and communications.
`Examples of words drawn from the electronics lexicon and not widely heard or
`seen just five years ago include compact disks (CDs), cellular radio, communications
`satellites, dynamic memory (D-RAM or DRAM), facsimile (FAX), fiberoptic cable, and laser
`printers. Those engaged in occupations within or related to the electronics field are
`sure to be aware of ASIC, CMOS, VMEbus, Multibus, cache, emulation, coprocessor, and
`Ethernet. There are frequent references to CJSC, RISC, SRAM, file servers, LANs,
`PLCCs, and PLDs.
`Despite the influx of new words and phrases, the classical vocabulary of
`electronics (largely adopted from electrical engineering) is still in wide circulation.
`These words are heard and written in the classroom, laboratory, repair shop, and
`factory. Some ter.minology has become obsolete and has disappeared along with the
`technology. There is little discussion these days of triodes, pentodes, selenium rectifiers,
`or even germanium transistors.
`This encyclopedia was edited to fill a gap in reference sources between the
`dictionary (or dictionary of electronics) and formal textbooks or handbooks for the
`electronics engineering professional. lt assumes that the average reader may want to
`know more about a subject than is given in a brief definition, yet may not be
`prepared to obtain that information from a professional-level text or handbook.
`
`7
`
`

`

`Even the reader with a formal background might not wish to take the time and
`make the effort to research the formal academic papers, journals, or texts just to find
`a simple, dear explanation of a topic in the field.
`The articles in this encyclopedia are descriptive. They make fewer demands on
`the reader's educational background in electronics than do more academically
`rigorous references. Mathematics is used sparingly, and then only when necessary
`to explain a topic. Encyclopedias of science and technology cover many of the same
`subjects, but in ten or more volumes-and they may not be up to date on
`leading-edge subjects.
`This en<..")'clopedia does not call for minimum educational level, although a basic
`knowledge of high school physics and chemistry or practical electronics would be
`helpful. The single volume is intended to satisfy the reader's "need to know" with
`more than jus t.a few sentences, any alternate meanings, and the correct spelling of
`the word or phrase. It is written to be a useful "stepping stone" or refresher for the
`reader wishing to delve deeper into specific subjects discussed in more advanced
`texts and papers.
`This second edition has introduced many new articles and illustrations not found
`in the first edition. Some of the topics covered in the first edition that are considered
`obsolete have been deleted to make room for newer topics believed to be of more
`interest to a wider group of readers. The result is a book of about the same length as
`the first edition with more emphasis on coverage of the latest developments in
`electronics and computer hardware.
`Because of its ongoing infiltration into all walks of human endeavor, even a
`fundamental knowledge of electronics is essential for an educated person. An
`otherwise well-informed person who has been "out of touch" with business and
`commerce for the past five years might have difficulty in reading and understanding
`some of today's popular articles without current knowledge. Articles on business,
`finance, and world economics now regularly cover the international electronics and
`computer industries, their products, and the politics of world trade.
`Even persons with college degrees are finding it necessary to take formal courses
`on such recent subjects as word processing, computer graphics, computer-aided
`design, and desktop publishing because of the complex nature of those subjects.
`This encyclopedia takes the view that computer science is a separate subject
`from, although it overlaps with, electronics. Thus the volume is neither a compre(cid:173)
`hensive encyclopedia of computers nor computer software; however, it contains
`many articles on topics in those fields. Selection was made on the basis of their
`relative importance to the wider field of electronics.
`
`11
`
`' I
`I
`
`-
`
`8
`
`

`

`. of t]1e normal signal. t he weaker the ios.tan\a(cid:173)
`;iJllJ?litt~:pli!tJde of the signal, the greater tbe.ampli(ica(cid:173)
`eoll5
`~otl wctor~ssion is often used in communications sys(cid:173)
`co~~prove intelligibility under poor conditions. See
`tePlS to f•RJ]SSION CIRCUIT, SPEECH COMPRESSION.
`dl5P coM .
`ss1·0N· c1Rcu1T·W•!¥•*~'*ttID%"g~~*-u
`I ,.
`l)MPRE
`W:lf:&~~-~wl'fr/§
`~ '
`ression circuit is an amplifier that displays vari(cid:173)
`A C9fl'lPin depending on the amplitude of the input
`a~le f:a Tl~e lo~er .the input signal level, the greater the
`.~gplifJcation factor. A compr~ssion circ·uit·ope.rate.s in a
`aroP . ·1
`· si.Jnilar to an automatic-level-control orcrnt. (see
`.
`"' ~ai;i.ne
`IJ\11C J.llVEL CONTl(OL).
`0
`Alf.TOOne method of obta~g compr~ssion i~ to .apply a
`'tifiea portion of the signal to the mput rucmt of the
`rec ~fying devic~, cha~~ing ~e bias a~ the signal amp~­
`~-changes. Thi~ rectified bias sl~ould reduce the gain
`~itJ1e,signal level mcreases; The time .constant mus.t be
`~:~JAste~ for th~ lea.stam·ountof distortion. An exam_pleis
`~shown in the diagram.
`There is a practical limit to the effectiveness of com-
`res.sion. Too much compression will cause the system to
`~ph:a.size acoustical noise. In a voice communications
`1ffif0~mltter, several decibels of effecti~e gain .can be
`'rea1~ed using .audio compression .. See.a/so.srEc:cn COMI'Rl.\sc
`IS[Q~\ I
`
`1
`
`+
`
`COMPUTER 197
`
`At a grazing angle !Jf collision, very little energy is
`transferred to the electron and the wavelength of the
`photon therefore increases only slightly (A in the illustra(cid:173)
`tion). At a sharper angle of collision (B), the photon loses
`more energy, and the change in wavelength.is greater . .At
`a nearly direct angle of collision, the wavelength change
`is the greatest, as shown at C.
`Compton effect causes the wavelength of X rays to be
`spread out when the radiation passes through an ob(cid:173)
`struction. See also x RAY.
`A.
`
`l\Mi ----- -
`
`Photon
`
`Electron o_
`
`-
`
`Electron
`
`B.
`'\NV
`e-- -
`Photon
`
`c.
`l\.N\J .--
`
`Photon
`
`-D \
`\
`_ _£-_~--0
`
`~
`
`~Electron
`
`COMPTON EFFECT: Changes in emitted wavelength from pho(cid:173)
`ton-electron collisions (Compton effect) are diagrammed. At a
`shallow angle the effect is negligible (A), at a sharper angle the
`effect increases (13), and a direct hit produces the maximum effect.
`
`Any device that aids in computation, from an abacus or
`slide rule to a mechanical adding machine or an elec(cid:173)
`tro~1ic.calcula tor, can be call~d a computer. Some electro(cid:173)
`mechar\ical machill'es based on gears, motors; cltitches,
`and other mechanisms use in the performance of special(cid:173)
`ized calculations have also been referred to as computers.
`In the 1940s and 1950s, electronic equipment, based on
`poten,tiometers andvacumn-tube operational amplifiers,
`capable of pcrform.i11g a wide range of analog computa(cid:173)
`.tions were referred to as computern.R owever, today, by
`common usage, the word computer has come to mean
`(and is used in this book) to mean a stored-program
`electronic digital computer. Figure 1 is a basic block
`diagram of a digit~! computer.
`An eleclTon.ic digital computer is distingµished from
`otht::r coaiputing·devices by its spe_ed, internal memory,
`and automatic execution of a program stored i.n its
`memory. The speed of an el~clTOnic computer is obt'!ffied
`with integrated circtii.t logic and memory devi~es.
`
`COMPRESSION CrRCUIT: A schematic for a compression circuit.
`
`;a M PTON EFFECT ;;t'tftlft~}B~fii~t~i~l~lfitrlJHJ
`
`tr hen photons (particles of radiant energy) strike elec-
`500ns, the wavelef)gth of the photons changes because
`'!'hill: Of the ehoton energy i~ transferred to the electrons.
`1'h e ~hange m wavelength 1s called the Compton effect.
`the illlloi.mt of change in the wavelength is a function of
`see scattering angle. Compton effect is generally ob(cid:173)
`. tved With X rays.
`
`9
`
`

`

`198 COMPUTER
`
`The internal memory of an electronic stored-program
`computer slores both data and instructions. A sequence
`of instructions for input, processing and output is per(cid:173)
`formed automatically, without human intervention. By
`contrast, an electronic calculator requires human direc(cid:173)
`tion from a keyboard at each step of the computation.
`The difference between an electronic calculator and a
`computer ·is significant. Electronic calculators accept
`numbers that are entered on a keyboard, and these
`numbers are stored in registers. The calculator then
`performs arithmetic operations, one at a time, as the
`various function keys are pressed. The calculator does
`not have true memory for data storage. By contrast, a
`computer stores and executes a program entered on the
`keyboard or from a storage medium, such as a magnetic
`tape or magnetic disk drive.
`
`Computer Types There are two basic types of elec(cid:173)
`tronic computers: analog computers and digital comput(cid:173)
`ers. Analog computers measure electrical or physical
`magnitudes, ·and digital computers count. See ANALOG
`COMPUTER.
`There is still a need for analog computation in science
`and engineering. This is being met with hybrid comput(cid:173)
`ers combining an analog computer with a digital com(cid:173)
`puter. The digital section performs counting and da ta
`processing.
`Many di ffe.rent digital computers are available to
`meet the very wide requirements for computation,
`graphics generation, word processing, accounting, pro(cid:173)
`cess control, and data processing. There are significant
`
`differences in capabilities, performance, size, form fac(cid:173)
`tor, and price in available digital computers today. New
`computers are becoming available with significant differ(cid:173)
`ences from the traditional or Von Neumann architecture.
`See coMl'lfrER ARO 1m;cruru;.
`The.re are also differences in input/output (I/O) pe(cid:173)
`ripheral devices in use. Printers and plotters are used to
`produce hard copy printed p ages. The CRT displays
`transactions and also is an interactive device. Other
`interactive devices include keyboards, light pens, the
`mouse, and data entry tablets.
`At the low end of the contpl.:lter hierarchy are the
`simple, low-cost microcomputers for playing electronic
`games on home television sets or canying out routine
`process co1lb·ol duties. At the next higher level there are
`the personal computers that offer a wide range of options
`and performance. At an even higher performance level
`are the mi11icomputers and the computer-aided design
`(CAD) graphics workstations. At the highest levels are
`the high-speed supercomputers used in making exten(cid:173)
`sive scientific and engineering calculations. Figure 2
`shows a personal computer.
`For many years, digital coinputers were simply
`classed as microcomputers (because of their use of micro(cid:173)
`processors-MPUs-as central processing units or
`CPUs), minicomputers, and mainframe computers. The
`term m icrocom pu ter has a dual meaning today. For some
`it means any computer with a microprocessor as a central
`processor (as opposed to a discrete component proces·
`sor); for others it has come to mean a computer-on-a-chip
`or a microcontroller (MCU). An MCU is an LSI silicon
`
`Address Bus
`
`Arithmetic
`and logic
`Unit(ALU)
`
`Registers
`
`Central Processing
`Unit(CPU)
`
`lnpuU
`Output
`Port
`(1/0)
`
`Data
`
`Control Bus
`
`Data Bus
`COMPUTER: Fig. 1. Block diagram of the organization of a digital computer.
`
`Read-Only
`Memory
`(ROM)
`
`Random
`flccess
`Memory
`(RAM)
`
`10
`
`

`

`. f'v{PUTER~ F~g. 2. Personal comput~r
`c~ d on a 32-bit microprocessor equ.ippea
`d d ·
`biiSr.
`with keyboar an mous~.
`
`I
`
`'· I
`I
`
`I
`
`I
`
`11
`
`chip containing a CPU, limited random access memory
`(RAM) and read-only memory (ROM), and on-chip (I/O)
`functions. See MICROPROCESSOR.
`Today the term personal c01i1puter (or PC) i·s under(cid:173)
`stood to meari. a general purpose desktop (or laptop) unit
`for computation, process conh'C'.11, word processing and
`even desktbp publishing. lt can also function as a sm·art
`video data terminal or VDT (See vmso DISPLAY t 1,mMil'IAL).
`Most personal computers fn use al'e based 011 8-bit arid
`16-bit microprocessors, but designs 01.1 32-b.it units are
`available.
`Workstations are a new classification of computers
`specialized for computer-aided design (CAD) and com(cid:173)
`puter-aided engineering (CAE) with heavy emphasis on
`graphics capability. (See COMPlITER-AIDED DESIGN ANO COM(cid:173)
`Pll'rER-AIDED ENGINEBIUNG.) Current generation workstations
`are based on 16-bit and 32-bit microprocessors.
`The term inihicompuler is still in use, but it is 1row
`defined more in terms of word length capability thnn its
`former industrial control specialty. Mostminicornptiters
`are based on 32-bit, custom-designed microprocessors.
`The term mainfraine computer today is ambiguous. It has
`
`been replaced by such terms as supercomputer, super
`minicomputer, and mini supercomputer.
`
`Computer Organization All digital computers, re(cid:173)
`gardless of size or complexity-from personal computers
`to supercomputers-have the i:.>ame functional compo(cid:173)
`nents as shown in Fig. 1. rlili? arrangement ·is named
`sequential machine architecture and it dates back to ·the
`World War II period of'1942to1945.'fo:omthis diagram it
`can be seen that the computer reads or inputs data from
`sources such as keyboards, modems, ·or secondary m~m­
`ory devices such as disk or tape drives. It writes or
`outputs to the CRT monitor and other devices such as
`printers.
`The ·computer has two kinds of memory tQ i:.>tore
`prtlgram instructio11s. a~ well a.s the data' that are being
`processed. The com.puter is under the direction cif ·a
`program and it 1rns a CPU (central processing unit) that
`interprets the program instruc;tions and supervises their
`execution.
`The computer also has a section that performs addi(cid:173)
`tion, division, and other arithmetic operations called the
`
`11
`
`

`

`l
`
`200 COMPUTER-AIDED DESIGN and COMPUTER-AIDED ENGINEERING
`
`ALU (arithmetic logic unit). The ALU can also perform
`logical operations such as comparing the magnitude of
`two numbers. The flow of data in Fig. 1 is on the data bus
`and the flow of control information is on the control bus.
`Ceritrnl Processing Unit (CJ.'U). The arithmetic and
`logic unit (ALO), .the control and tinting unit, and the
`registers are ·integrated into a single phy,~kal unit c~lled
`the central p1'oces's'ing unit ·or CPU. The'~PU is thq brain
`or nerve center of a computer: It cont~ols the operation of
`the computer through the co1Jtrol and timing unit and
`performs arithmetic and 'logical operations thrpugh the
`arithmetic and logic unit. See ARJTI-IMIITIC.LOGJC l}NIT.
`Control and Timing Unit. The control and tinting unit
`supervises all operations of th~ computer w:rd~r direction
`of a stored program. First the control and timing unit
`determines whii::h instruction is to be !??Ce,cuted next by
`the computer. The control and timing urut then fetches
`the instruction from the main memory and interprets the
`instruction. The instruction is then executed by other
`computer units, i.mder the dii'ectibiygf the control unit.
`Tlze .Arithmetic Logic UnU (ALU)'. l'he /\LU performs
`computatio_ns and data manipulations ~udt.as addition,
`subtraction, comparison, and logical op~rations. A typi(cid:173)
`cal logical operation involves comparlt}.g two numbers,
`and then selecting one of two (or more) program paths
`depending on the result Qf the co~pa~on. -See ARrntMEllC
`LOGIC UNIT.
`Acting in harmony with the control and timing unit,
`the ALU can test numbers and cause the computer to
`branch to pqe of two possible program paths. This ability
`to ~est or cqmpare two numbers and. to branch fo one of
`several paths depending on the results of the comparison
`gives the- computer great power and flexibility. It is a
`major reasqn -why the digital computer i~ so useful in
`many different applications.
`Mni11 Memory. A computer must have a memory for
`storage of <;lata and instructions. This memory can be in
`three levels: primary, secondary, an_d tertiary. The com(cid:173)
`puter main memory consists of array~ of semiconductor
`memory devices. Data and insbucti9_ns -are stored in
`area.~ called Jo9ations. Each focation in_main memory has
`an address so that data can be located. The capacity of
`main memory is determined by the size and application
`of the computer.
`The computer central processing unit (CPU) can only
`operate on the data from the main memory, and only
`instructions from the main memory can control the
`computer. The basic building block of a computer main
`memory is the integrated circuit semiconductor memory.
`Each memory IC (integrated circuit) contains thousands
`of transistors that function as switches in representing
`the binary digits zero·and,0ne.(SeeSE~IC01'JD.UCTORfy1UMORY.)
`In most computers, main memory lS <;tivicled 'into sec(cid:173)
`tions. For example, there is often a division between
`random access memory (RAM) and read-only memory
`(ROM) as shown in the figure.
`Main memory· is usually s upplemented by seconda1y
`storage mass memory which includes floppy-disk drives,
`rigid-disk drives (typically Winchester type). These
`memory devices are random access memories that can
`
`read and write data rapidly, making them virtual main
`memories. See DISK DRIVE.
`Demand-Paged. Demand-paged memory systems di(cid:173)
`vide bpth disk and RAM (virtual and physical) memories
`into fixed-sized pages. ln moving from disk to RAM,
`blocks of information are switched into the same number
`of pages: Demand-paged virtual memory permits multi(cid:173)
`ple users and multiprocessing. Segmented memory sysc
`terns iinpose partitions on RAM. This s~gmentation must
`accomnmdate the longest program or data constn.tct
`needed.
`Many computer systems ats·o have tertiary memory
`that serVe as backup, long-term, or archival data and
`program storage. The most commonly used tertiary
`memories are magnetic tape drives with the memory
`media in the form of tape cassettes or tape reels(cid:173)
`(strean}ing tape). Tape drives are serial-access memories
`with..r!!latively Jong access times. Write-once, read-many
`(WORM). optical disk drives and compact disk (CD)
`ROMs are now also being. used for data storage. See
`COMPACT DISK, OPTICAL DISK DRIVE.
`
`COMPUTER-AIDED DESIGN
`and COMPUTER-AIDED
`ENGINEERING lt~S)i~~;;;;-r";':K;:;,:iil@1i''-£'°'&"..;;s;:,o:;l&;!;~flM£'$Jii1'!
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`Computers are now widely us~d in the design and
`.manufa~h.ire of products and sy~t!!ffis. Computer.·aided
`9.e~ig1~ (CAD) and computer-aiqed engineering (CAE)
`refer to the use of computers to aid the designer from
`product conception through the preparation of engineer(cid:173)
`ing drawings, specifications, and parts lists. Computers
`.can develop elevation views and three-dini.ensional
`drawings of engineering structures,.analyze those struc(cid:173)
`tures, and prepare manufacturing drawings. They can
`also perform interference checking, tool-path definition,
`parts listing, and numerical control (NC) tape prepara(cid:173)
`tion.
`Computer-aidec\ manufocturing .. (CAM) refers to ~1e
`use of comput.e~s in in.v~n~ory. and' quality control as v:ell.
`as the superv1s10n and direct control of manufacturmg
`machines and processes. [deaily d~sig:n concepts origi(cid:173)
`nated at the CAD/CAE level are transferred directly into
`instructions for the manufacture of products bec9use
`they share a common database. The same database can
`be used for testing, quality control, inventory control and
`production scheduling.
`Computer-aided design has ev9lved from automatic
`drafting. The. computer-based video workstation tenni(cid:173)
`nal displayed the end propuct a~ .a two-dimensional
`representation of a conventional engineering drawing.
`Information on the third dimension was obtained from
`orthogonal views.
`However, in the design of circuit boards and inte(cid:173)
`grated circuits, the third dimension could be introduced
`by displaying layers positioned and registered on one
`another. Design work can be done on individual layers
`and a composite presentation can distinguish each layer
`by means of color coding. By following sets of rules
`
`12
`
`

`

`,
`
`r·· 1 rogrammed into the computer, wiring runs and inter(cid:173)
`
`~onnects can be made without overlap or interference.
`Computer solids modeling was developed for the
`design of more complex objects such as machines, ships,
`·and aircraft. The object can be represented on the screen
`~~;-a . thr~e-dimensional lli1e drawing that can be moved
`~bout in space. These presentations suggested isometric
`drawings. With further developments these wire-frame
`unages could be filled in to achieve solids modeling and
`surface modeling in shades of gray or colors.
`Finite element analysis (FEA) was a CAD develop(cid:173)
`ment that enabled a complex solid structure is broken
`down into a large number of simple elements so each
`simple element could be· analyzed. For example, the
`forces on the structure or: loading of building, ship, or
`aircraft structures could be analyzed.
`Computer-aided engineering i~ an outgrowth of com(cid:173)
`puter-aided design, and it becomes increasingly difficult
`to distinguish the difference between them. Engineering
`software h as been developed to permit the solution of
`problems other than stress analysis. For example, electri(cid:173)
`cal and electronic circuit problems can now be solved
`with programs that analyze the specific circuits displayed
`in schematic form. Data and design rules on the physical
`and electrical characteristics of components are stored in
`memory to be called up as needed.
`CAE systems permit circu it simulation at the abstract
`symbolic level. Substitution of components can be made
`in the models to determine their effect on circuit perfor(cid:173)
`mance. This simulation saves on the cost of completing
`drawings and building hardware prototypes. CAE seeks
`to analyze and optimize designs in many fields of engi·
`neering.
`Computer-aided testing (CAT) is another outgrowth
`of computer-aided design and engineering. The electrical
`characteristics of devices, components, and subsystems
`can.be stored in computer memory for comparison with
`actual measured characteristics· with the computer-aided
`test equipment. CAT systems speed up the testing of
`complex integrated circuits in wafer form or as packaged
`devices. They can also test complete circuit boards and
`subsystems. CAT systems can provide printed .records of
`p_roduct testing and can even direct the marking. and
`eiection of failures from production lines.
`Computer-aided manufacturing is an outgrowth of
`the numerical control (NC) of machines. NC machines
`Were designed for digital control of the machine by a
`program introduced on a punched and coded paper tape.
`Computers can now control banks of NC machining
`centers, milling machines, or lathes in a hierarchical
`organization known as computer numerical' control
`(CNC). They can also manage tool wear and replace(cid:173)
`ment, scheduling, parts. resitpply, productivity, and
`other adfninistrative details.
`L{obots are example m<ichines that are directly con(cid:173)
`t:olled by computers. General-purpose robots are modi(cid:173)
`fied by the installation of special tooling to p erform a
`ra~ge of specific tasks such as arc welding, spot welding,
`Painting, gluing and assembly. The robot can be taught
`
`COMPUTER-AIDED MEDICAL IMAGING 20 I
`
`by manually leading it through the task so that the robot
`memory will store a record of the movements of each
`robot axis in thr.ee dimensions. The robot controller then
`replays the sequence on command when the work is to
`be done automatically. Some robots can also be pro(cid:173)
`gramed off line by writing programs based on assem(cid:173)
`bling standardized sequences without tying up the robot
`for teaching. See ROBOT.
`Many kinds of specialized machines that do not
`qualify as robots such as automatic pick-and-place ma(cid:173)
`chines for inserting or positioning electronic component
`on circuit boards may also be controlled by a computer.
`Separate programs are prepared giving the location of
`each leaded or surface mount component and this infor(cid:173)
`mation is stored in a computer memory library as in the
`case of robots.
`Computer vision (CV) systems can be programed to
`recognize specific objects in a field of similar objects for
`sorting. They can also be used to inspect parts for quality
`or completeness by comparing their images against a
`master image stored in memory. See COMPUTER v1s10N.
`Computer integrated manufacturing (CIM) seeks to
`combine and standardize communications among differ(cid:173)
`ent kinds of workstations and different software to per(cid:173)
`mit a totally integrated factory. Basic design information
`can be developed off line at a laboratory or factory and be
`transmitted over compatible communications lines and
`bus structures to permit the organization of factories
`from a centralized hierarchical computer.
`tJnder CIM, all phases of design engineering, plan(cid:173)
`ning, manufacture, and inventory control can be under
`centralized control. This activity is in its early stages.
`Adherents of the concept are encountering the problems
`of c0mmunication between disparate systems and soft(cid:173)
`ware as well as the unwillingness of 1mmy suppliers of
`embedded computers and software to subordinate their
`products to an overall supervisory control system.
`
`COMPUTER-AIDED
`MEDICAL IMAGING ill&t$4t1@11::tl~~imliliftffem
`Computer-aided m edical imaging refers to a number of
`different techniques that permit physicians and surgeons
`to view the inside of the human body without intrusive
`surgery. Signals obtained from X rays, nuclear magnetic
`resonance, ultrasonic waves, and radioactive isotopes,
`for example, are organized by computers and applica(cid:173)
`tions software to present views of living human beings
`unobtainable with earlier X ray and sonogram methods.
`The views are typically presented on a cathode ray tube
`(CRT). (See CATHODE RAY TUBE.) These scans permit doctors
`to watch vital organs at work, identify blockages and
`growths, detect disease, and even detect warning signs
`of diseases not yet present-all without exploratory su