The IEEE Standard Dictionary of
`Electrical and Electronics Terms
`
`Sixth Edition
`
`Standards Coordinating Committee 10, Terms and Definitions
`Jane Radatz, Chair
`
`This standard is one of a number of information technology dictionaries being developed by standards
`organizations accredited by the American National Standards Institute. This dictionary was developed
`under the sponsorship of voluntary standards organizations, using a consensus-based process.
`
`ISBN 1-55937-833-6
`90000
`
`9 781559 378338
`
`c~ er/ ,-f l J
`
`1
`
`APPLE 1016
`
`

`

`Introduction
`
`Since the first edition in 1941 of the American Standard Definitions of Electrical Terms, the work now
`known as IEEE Std 100, The IEEE Standard Dictionary of Electrical and Electronics Terms, has evolved
`into the unique compendium of terms that it is today.
`
`The current edition includes all te1ms defined in approved IEEE standards through December 1996. Terms
`are categorized by their technical subject area. They are also associated with the standards or publications
`in which they currently appear. In some cases, terms from withdrawn standards are included when no
`cunent source can be found. Earlier editions of IEEE Std 100 included te1ms from sources other than
`IEEE standards, such as technical journals, books, or conference proceedings. These terms have been
`maintained for the sake of consistency and their sources are listed with the standards in the back of the
`book.
`
`The practice of defining terms varies from standard to standard. Many working groups that write standards
`prefer to work with existing definitions, while others choose to write their own. Thus terms may have
`several similar, although not identical, definitions. Definitions have been combined wherever it has been
`possible to do so by making only minor editorial changes. Otherwise, they have been left as written in
`the original standard.
`
`Users of IEEE Std 100 occasionally comment on the surprising omission of a particular term commonly
`used in an electrical or electronics field. This occurs because the terms in IEEE Std 100 represent only
`those defined in the existing or past body of IEEE standards. To respond to this, some working groups
`obtain authorization to create a glossary of te1ms used in their field. All existing, approved standard
`glossaries have been incorporated into this edition of IEEE Std 100, including the most cun-ent glossaries
`of terms for computers and power engineering.
`
`IEEE working groups are encouraged to refer to IEEE Std 100 when developing new or revised standards
`to avoid redundancy. They are also encouraged to investigate deficiencies in standard terms and create
`standard glossaries to alleviate them.
`
`The sponsoring body for this document was Standards Coordinating Committee 10 on Definitions
`(SCClO), which consisted of the following members:
`
`John W. Balde
`Arthur Ballato
`Bruce Barrow
`William Carey
`Frank A. Denbrock
`Jay Forster
`
`Jane Radatz, Chair
`
`Chris Heegard
`John Horch
`J. L. Koepfinger
`Allen I-I. Meitzler
`Frank D. Myers
`David E. Roberts
`
`F. A. Saal
`Ralph M. Showers
`Edward N. Skomal
`Kenneth L. Swinth
`Raymond S. Turgel
`Edward F. Vance
`
`2
`
`

`

`When the IEEE Standards Board approved this standard on 10 December 1996, it had the following
`membership.
`
`Richard J. Holleman, Vice Chair
`Donald C. Loughry, Chair
`Andrew G. Salem, Secretary
`
`Gilles A. Baril
`Clyde R. Camp
`Joseph A. Cannatelli
`Stephen L. Diamond
`Harold E. Epstein
`Donald C. Fleckenstein
`Jay Forster*
`Donald N. Heirman
`Ben C. Johnson
`
`*Member Emeritus
`
`E.G. "Al" Kiener
`Joseph L. Koepfinger*
`Stephen R. Lambert
`Lawrence V. McCall
`L. Bruce McClung
`Marco W. Migliaro
`Mary Lou Padgett
`John W. Pope
`
`Jose R. Ramos
`Arthur K. Reilly
`Ronald H. Reimer
`Gary S. Robinson
`Ingo Rusch
`John S. Ryan
`Chee Kiow Tan
`Leonard L. Tripp
`Howard L. Wolfman
`
`Also included are the following nonvoting IEEE Standards Board liaisons:
`
`Satish K. Aggarwal
`Alan H. Cookson
`Chester C. Taylor
`
`Kim Breitfelder (1995-present), IEEE Std JOO Editor
`Stephen Huffman (1993-1995), IEEE Std 100 Editor
`
`Assistance was provided by the IEEE Standards editorial staff.
`
`How to use this dictionary
`
`The terms defined in this dictionary are listed in letter-by-letter alphabetical order. Spaces are ignored in
`this style of alphabetization, so cable value will come before cab signal. Descriptive categories associated
`with the tem1 in earlier editions of IEEE Std 100 will follow the tenn in parentheses. New categories
`appear after the definitions (see Categories, below), followed by the designation of the standard or stan(cid:173)
`dards that include the definition. If a standard designation is followed by the letter s, it means that edition
`of the standard was superseded by a newer revision and the term was not included in the revision. If a
`designation is followed by the letter w, it means that edition of the standard was withdrawn and not
`replaced by a revision. A bracketed number refers to the non-IEEE standard sources given in the back
`of the book.
`
`Acronyms and abbreviations are no longer listed in a separate section in the dictionary; rather, they are
`incorporated alphabetically with other tenns. Each acronym or abbreviati01;1 refers to its expanded term,
`where it is defined. Acronyms and abbreviations for which no definition was included in past editions
`have been deleted from this edition of IEEE Std 100.
`
`Abstracts of the current set of approved IEEE standards are provided in the back of the book. It should
`be noted that updated information about IEEE standards can be obtained at any time from the IEEE
`Standards World Wide Web site at http://standards.ieee.org/.
`
`Categories
`
`The category abbreviations that are used in this edition of IEEE Std 100 are defined below. This infor(cid:173)
`mal ion is provided to help elucidate the context of the definition. Older terms for which no category could
`he found have had the category "StdlO0" assigned to them. Note that terms from sources other than IEEE
`standards, such as the National Electrical Code® (NEC®) or the National Fire Protection Association,
`may not be from the most recent editions; the reader is cautioned to check the latest editions of all sources
`for the most up-to-date terminology.
`
`iv
`
`AE
`AH[
`AMF
`AP
`ATL
`BA
`BT
`C
`CAS
`CE
`CHI\
`C01'
`cs
`DA
`DEI
`DES
`DIS
`ED
`EDl
`EEC
`EL1'
`EM
`EM]
`EM
`GR!
`GSI
`IA
`IE
`II
`IM
`IT
`!VI(cid:173)
`LE<
`LM
`MA
`MIJ
`M1
`MT
`NE
`NE
`NF
`NI
`Nil
`NJ\
`NP
`0[
`OE
`PA
`PE
`PE
`PQ
`PS
`P\i
`Ql
`R
`RJ
`RI
`
`3
`
`

`

`acy test
`
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`7], [57]
`1rmers)
`1 estab-
`0-1996
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`n eJTor,
`rticular
`5-1990
`rhe ac(cid:173)
`e limit,
`that er(cid:173)
`ler ref(cid:173)
`tended
`tin an
`'arious
`:d that
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`class.
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`he in(cid:173)
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`point
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`Ned
`ms(cid:173)
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`
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`der
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`the
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`re-
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`1m
`
`ACD
`
`9
`
`acknowledger
`
`the secondary reflects the value of the quantity applied to the
`primary.
`(PE)
`[57]
`ACD See: automatic call distribution.
`ac-dc general-use snap switch A form of general-use snap
`switch suitable for use on either ac or de circuits for control(cid:173)
`ling the following:
`
`a) Resistive loads not exceeding the ampere rating of the
`switch at the voltage applied.
`b) Inductive loads not exceeding 50% of the ampere rating of
`the switch at the applied voltage. Switches rated in horse(cid:173)
`power are suitable for controlling motor loads within their
`rating at voltage applied.
`c) Tungsten-filament lamp loads not exceeding the ampere
`rating of the switch at the applied voltage if "T" rated.
`
`(NEC/NESC)
`
`(86]
`
`ACE See: area control eJTor.
`ac electric field strength The electric field strength produced
`by ac power systems as defined by its space components
`along three orthogonal axes. For steady-state sinusoidal fields,
`each component can be represented by a complex number or
`phasor. The magnitudes of the components are expressed by
`their rms values in volts per meter, and their phases need not
`be the same. Notes: 1. A phasor is a complex number ex(cid:173)
`pressing the magnitude and phase of a time-varying quantity.
`Unless otherwise specified, it is used only within the context
`of linear systems driven by steady-state sinusoidal sources.
`In polar coordinates, it can be written as Aei<P where A is the
`amplitude or magnitude (usually rms but sometimes indicated
`as peak value) and cp is the phase angle. The phase angle
`should not be confused with the space angle of a vector.
`2. The space components (phasors) are not vectors. The space
`components have a time-dependent angle while vectors have
`space angles. For example, the sinusoidal electric field
`strength, E, can be expressed in rectangular coordinates as
`"£ = a,E, + ayEy + aZEZ
`where, for example, the x component is
`E, = Re (£,0 ej'1" ejwt) = Exo cos (cpx + wt)
`The magnitude, phase, and time-dependent angle are given
`by Exo, <Px, and ( <J:,, + wl), respectively. In this representation,
`the space angle of the x component is specified by the unit
`vector a,. An alternative general representation of a steady(cid:173)
`state sinusoidal electric field can be derived algebraically
`from equation I above and is perhaps more useful in char(cid:173)
`acterizing power-line fields because the fields along the di(cid:173)
`rection of the line are small and can usually be neglected. It
`is a vector rotating in a plane where it describes an ellipse
`whose major semi-axis represents the magnitude and direc(cid:173)
`tion of the maximum value of the electric field, and whose
`minor semi-axis represents the magnitude and direction of the
`field a quarter-cycle later. As mentioned above, the electric
`field in the direction perpendicular to the plane of the ellipse
`is assumed to be zero. See also: polyphase ac fields; single(cid:173)
`(PE/T&D) 539-1990
`phase ac fields.
`ac electric field strength meter (1) A meter designed to mea(cid:173)
`sure the power-frequency electric field. Two types of electric
`field strength meters are in common use.
`(PE/T&D) 539-1990
`(2) A meter designed to measure ac electric fields. Three types
`of electric field strength meters are available-free-body
`meter, ground-reference meter, and electro-optic meter.
`(PE/T&D) 1308-1994
`acetate disks Mechanical recording disks, either solid or lami(cid:173)
`nated, that are made of various acetate compounds.
`(SP)
`
`[32]
`
`ACF See: access control field.
`ac filter Resistor-capacitor circuits connected in three-phase
`wye or delta on the ac terminals of a converter.
`(IA) 995- l 987w
`
`ac general-use snap switch A form of general-use snap switch
`suitable only for use on alternating-current circuits for con(cid:173)
`trolling the following:
`
`a) Resistive and inductive loads, including electric-discharge
`lamps, not exceeding the ampere rating of the switch al the
`voltage involved.
`b) Tungsten-filament lamp loads not exceeding the ampere
`rating of the switch at 120 V.
`c) Motor loads not exceeding 80% of the ampere rating of
`the switch at its rated voltage.
`
`(NEC/NESC) [86]
`achromatic locus (achromatic region) (television) A region
`including those points in a chromaticity diagram that repre(cid:173)
`sent, by common acceptance, arbitrarily chosen white points
`(white references). Note: The boundaries of the achromatic
`locus are indefinite, depending on the tolerances in any spe(cid:173)
`cific application. Acceptable reference standards of illumi(cid:173)
`nation (commonly refeJTed to as white light) are usually rep(cid:173)
`resented by points close to the locus of Planckian radiators
`having temperatures higher than about 2000 °K. While any
`point in the achromatic locus may be chosen as the reference
`point for the determination of dominant wavelength, comple(cid:173)
`mentary wavelength, and purity for specification of object
`colors, it is usually advisable to adopt the point representing
`the chromaticity of the illuminator. Mixed qualities of illu(cid:173)
`mination and luminators with chromaticities represented very
`far from the Planckian locus require special consideration.
`After a suitable reference point is selected, dominant wave(cid:173)
`length may be detennined by noting the wavelength c01Te(cid:173)
`sponding to the intersection of the spectrum locus with the
`straight tine drawn from the reference point through the point
`representing the sample, When the reference point lies be(cid:173)
`tween the sample point and the intersection, the intersection
`indicates the complementary wavelength. Any point within
`the achromatic locus chosen as a reference point may be
`called an achromatic point. Such points have also been called
`(BT) 201-l979w
`white points.
`acid-resistant So constructed that it will not be injured readily
`by exposure to acid fumes.
`(IA)
`[60], [75]
`ACK See: acknowledge character.
`ack cycle A cycle in which a slave responds to a master and
`terminates a transaction,
`(C/MM)
`l l 96-1987
`acknowledge An acknowledge packet.
`(C/MM) 1394-1995
`acknowledge bit A bit used by IEEE 802.3 Auto-Negotiation
`to indicate that a station has successfully received multiple
`identical copies of the Link Code Word. This bit is only set
`after an identical Link Code Word has been received three
`(C/LM) 802.3u-l 995
`times in succession.
`acknowledge character (ACK) (A) A transmission control
`character transmitted by a station as an affirmative response
`to the station with which the connection has been set up.
`(B) A transmission control character transmitted by a receiver
`as an affirmative response to a sender. An acknowledge char(cid:173)
`acter may also be used as an accuracy control character. See
`also: negative acknowledge character.
`(C) 6!0.5-1990
`acknowledge gap The period of idle bus between the encl of a
`packet and the start of an acknowledge.
`(C/MM) 1394-1995
`acknowledge packet (1) A link-layer packet returned by a des(cid:173)
`tination node back to a source node in response to most pri(cid:173)
`mary packets. An acknowledge packet is always exactly 8
`bits long.
`(C/MM) 1394-1995
`(2) The first packet returned by an individually addressed S(cid:173)
`module that conveys to the M-module that the appropriate S(cid:173)
`module is responding and indicates the cmTent status of the
`(C/TT) 1149.5-1995
`responding S-modulc.
`acknowledger (forestaller) A manually operated electric
`switch or pneumatic valve by means of which, on a loco(cid:173)
`motive equipped with an automatic train stop or train control
`device, an automatic brake application can be forestalled, or
`
`4
`
`

`

`acknowledging
`
`10
`
`across-the-line starter
`
`by means of which, on a locomotive equipped with an auto(cid:173)
`matic cab signal device, the sounding of the cab indicator can
`(EEC/PE) [l 19]
`be silenced.
`acknowledging (forestalling) The operating by the engineman
`of the acknowledger associated with the vehicle-carried
`equipment of an automatic speed control or cab signal system
`to recognize the change of the aspect of the vehicle-caJTied
`signal to a more restrictive indication. The operation stops the
`sounding of the warning whistle, and in a locomotive
`equipped with speed control, it also forestalls a brake appli(cid:173)
`(EEC/PE) [ I 19]
`cation.
`acknowledging device See: acknowledger.
`acknowledging switch See: acknowledger.
`acknowledging whistle An air-operated whistle that is sounded
`when the acknowledging switch is operated. Its purpose is to
`inform the fireman that the engineman has recognized a more
`(EEC/PE) (119]
`restrictive signal indication.
`acknowledgment See: acknowledgment of a message.
`acknowledgment of a message A reply transmitted by a re(cid:173)
`ceiving station to inform the sending station that a message
`has aJTived and the message is eJTor-free. Synonym: acknowl(cid:173)
`edgment. Contrast: negative acknowledgment.
`(C) 610.7-1995
`
`ACL See: audit command language.
`a contact A contact that is open when the main device is in the
`standard reference position and that is closed when the device
`is in the opposite position. Notes: 1. a contact has general
`application. However, this meaning for front contact is re(cid:173)
`stricted to relay parlance. 2. For indication of the specific
`point of travel at which the contact changes position, an ad(cid:173)
`ditional letter or percentage figure may be added to a. See
`also: standard reference position.
`(PE/SWG) C37.I00-1992
`acoustic absorber Material with high acoustic Joss placed on
`any part of the substrate for acoustic absorption purposes.
`(UFFC)
`I 037-1992
`acoustical depth finder See: echo sounder.
`acoustically tunable optical filter An optical filter that is driven
`by an acoustic wave and that is tunable by varying the acous(cid:173)
`tic frequency.
`(UFFC) [17]
`acoustic coupler (1) A type of data communication equipment
`that has sound transducers that permit the use of a telephone
`handset as a connection to a voice communication system for
`the purpose of data transmission.
`(COM/LM)
`l 68- I 956w
`(2) A modem that interconnects a communicating device with
`a telephone handset.
`(C) 610.7-1995
`acoustic delay line (1) A delay line whose operation is based
`on the time of propagation of sound waves.
`(C) [20], [85]
`(2) A delay line whose operation is based on the time of
`propagation of sound waves within a given medium. Syn(cid:173)
`onym: sonic delay line. See also: mercury storage.
`(C) 610.10-1994
`acoustic echo path (1) In a telephone set, the coupling from the
`receiver to the microphone (or transmitter)
`(COM) 269-1992
`(2) In a handset or headset system, the coupling from the
`receiver to the microphone (or transmitter).
`(COM) 1206-1994
`acoustic-gravity wave (radio-wave propagation) In the at(cid:173)
`mosphere, a low-frequency wave whose restoring forces are
`compressional, gravitational and buoyant.
`(AP) 211-1990
`acoustic input The free-field sound pressure level developed by
`an artificial mouth at the mouth reference point. See also:
`sound pressure level.
`(COM) 1206-1994, 269-1992
`acoustic interferometer An instrument for the measurement of
`wavelength and attenuation of sound. Its operation depends
`upon the interference between reflected and direct sound at
`the transducer in a standing-wave column. See also: instru(cid:173)
`(EEC/PE) [119]
`ment.
`acoustic memory See: acoustic storage.
`acoustic nuisc Sce: audible noise.
`
`acoustic output The sound pressure level developed in an ar(cid:173)
`tificial ear. See also: sound pressure level.
`(COM) 1206-1994, 269-1992
`acoustic propagation loss Amplitude decay of the acoustic
`wave due to material damping; scattering caused by defects,
`surface finish, or electrodes; and acoustic bulk-wave radiation
`into the ambient environment. Specifically, this is the ratio of
`the power transmitted in a surface acoustic wave (SAW)
`beam to the power received, expressed in dB.
`(UFFC) 1037-1992
`acoustic radiator A means for radiating acoustic waves.
`(EEC/PE) [ 119]
`acoustic regeneration The generation of a secondary acoustic ,.
`wave by the potential variations of an electrode caused by a
`primary surface acoustic wave passing under it.
`(UFFC) 1037-1992
`acoustic storage A type of storage consisting of acoustic delay
`lines.
`(C) 610.10-1994
`acoustic tablet A data tablet on which the position of the sensor
`or stylus is determined by acoustic sensing techniques.
`(C) 610. l0-1994
`acoustic wave filter A filter designed to separate acoustic waves
`of different frequencies. Note: Through electroacoustic trans(cid:173)
`ducers, such a filter may be associated with electric circuits.
`(EEC/PE) [ 119]
`See also: filter.
`acoustic waveguide A perturbation along the direction of prop(cid:173)
`agation of a surface acoustic wave to produce a decreased
`phase velocity, and hence, transverse concentration and guid(cid:173)
`ing of the surface acoustic wave.
`(UFFC) 1037-1992
`acousto-optic device A device that is used to modulate light in
`amplitude, frequency, phase, polarization, or spatial position
`by virtue of optical diffraction from an acoustically generated
`diffraction grating.
`(UFFC)
`(23]
`acousto-optic effect (fiber optics) A periodic variation of re(cid:173)
`fractive index caused by an acoustic wave. Note: The acousto(cid:173)
`optic effect is used in devices that modulate and deflect light.
`(Stcl!O0) 812-1984w
`See also: modulation.
`ac power-line fields Power frequency electric and magnetic
`fields produced by ac power lines.
`(PE/T&D) 539- I 990
`acquirer (1) An organization that procures software products
`for itself or another organization.
`
`(C/SE) J-STD-016-1995
`(2) A person or organization that acquires or procures a sys(cid:173)
`tem or software product (which may be part of a system) from
`a supplier.
`(C/SE) 1062-1993
`acquisition (1) The process of obtaining a system or software
`(C/SE) 1062-1993
`product.
`(2) The process of establishing a stable track on a target that
`is designated in one or more coordinates. A search of a limited
`given volume of coordinate space is usually required because
`of eJTors or incompleteness of the designation.
`( AE) 686- l 990w
`acquisition phase The final phase of the arbitration operation
`entered after detennining that an agent has the highest priority
`and the bus is available. See also: agent; arbitration operation.
`(C/MM) 1296-1987s
`acquisition probability The probability of establishing a stable
`track on a designated target.
`(AE) 686- l 990w
`acquisition start time The start time of the acquisition of the
`histogram data, as
`DD/MM/YR-HH:NN:SS_
`where the '_' (underscore character) is an ASCII space; DD
`is the day; MM is the month; YR is the year; HH is the hours;
`NN is the minutes; and SS is the seconds.
`(NPS) 1214-1992
`across-the-line starter ( electric installations on shipboard) A
`device that connects the motor to the supply without the use
`of a resistance or autotransformer to reduce the voltage. It
`may consist of a manually operated switch or a master switch,
`which energizes an electromagnetically operated contactor.
`(IA) 45- I 983r
`
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