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1、IEEE Std 599-1985 IEEE Standard Definitions of Power Systems Data Xkansmission and Related Channel Terminology Sponsor Power Systems Communications Committee of the IEEE Power Engineering Society Copyright 1985 by The Institute of Electrical and Electronics Engineers, Inc 345 East 47th Street, New Y
2、ork, NY 10017, USA No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher. Authorized licensed use limited to: Tsinghua University Library. Downloaded on December 25,2010 at 11:02:05 UTC from IE
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12、 apply. Foreword (This Foreword is not a part of IEEE Std 599-1985, IEEE Standard Definitions of Power Systems Data Transmis- sion and Related Channel Terminology.) d-1_ U% for example, in a linear detector the desired relation is between the out- put signal voltage and the input modulation envelope
13、; or the modulation of the input carrier and the resultant detected signal. amplitude modulation. The process by which a continuous high-frequency wave (carrier) is caused to vary in amplitude by the action of another wave containing information. The usual procedure is to key the carrier wave on and
14、 off in accordance with the data to be transmitted. For example, a 1170 Hz tone (the carrier) could be off for space and on for mark. This method has several disadvantages. It does not use bandwidth efficiently, since two sidebands of the carrier are produced and, unlike single sideband voice commun
15、ication methods, the carrier and one sideband cannot be completely eliminated and still do a satis- factory job. The information carrying char- acteristics of an am signal is its amplitude. analog. Used to describe a physical quantity - such as voltage or shaft position - that nor- dally varies in a
16、 continuous manner. analog channel. A channel on which the in- formation transmitted can take any value be- tween the limits defined by the channel. Voice channels are analog channels. antenna. A means for radiating or receiving radio waves. aperture (antenna). That portion of a ply-ie surface (for
17、an unidirectional antenna) near the antenna perpendicular to the direction of maximum radiation through which the major part of the radiation passes. artificial line. An electric network which simulates the electrical characteristics of a line over a desired frequency range. NOTE: Although the term
18、is basically applied to the case of simulation of an actual line by extension, it is used to refer to all periodic lines which may be used for laboratory purposes in place of actual lines, but which may represent no physically realizable line. For example, an artificial line may be composed of pure
19、resistances. asynchronous transmission. See: nonsynchro- nous transmission. 5 Authorized licensed use limited to: Tsinghua University Library. Downloaded on December 25,2010 at 11:02:05 UTC from IEEE Xplore. Restrictions apply. IEEE Std 599-1985 IEEE STANDARD DEFINITIONS OF POWER attenuation. A gene
20、ral term used to denote a decrease in signal magnitude in transmission from one point to another. Attenuation may be expressed in decibels or as a scalar ratio of the input magnitude to the output magnitude. attenuation distortion (frequency distortion). Either departure in a circuit or system from
21、uniform amplification or attenuation over the frequency range required for transmission, or the effect of such departure on a transmitted signal. attenuation equalizer. A corrective network which is designed to make the absolute value of the transfer impedance (with respect to two chosen pairs of te
22、rminals) substantially con- stant for all frequencies within a desired range. attenuator. An adjustable device for reducing the amplitude of a wave without introducing distortion. An adjustable passive network that reduces the power level of a signal without in- troducing appreciable distortion. aud
23、io. A term pertaining to frequencies cor- responding to a normally audible sound wave. NOTE: These frequencies range roughly from 15 Hz to 20 000 Hz. automatic frequency control (afc). An ar- rangement whereby the frequency of an oscil- lator of the tuning of a circuit is automati- cally maintained
24、within specified limits with respect to a reference frequency. automatic gain control (agc). A method of automatically obtaining a substantially con- stant output of some amplitude characteristic of the signal over a range of variation of that characteristic at the input. The term is also ap- plied
25、to a device for accomplishing this result. automatic volume control (avc). A method of automatically obtaining a substantially con- stant audio output volume over a range of in- put volume. The term is also applied to a de- vice for accomplishing this result. back scattering coefficient B (echoing a
26、rea). The back scattering coefficient B of an object for an incident plane wave is 4 7 1 times the ratio of the reflected power per unit solid angle usually expressed in bits per second. block. (1) A set of things, such as words, characters, or digits handled as a unit. (2) A collection of contiguou
27、s records re- corded as a unit. (3) In data communications, a group of con- tiguous characters formed for transmission purposes. block error. A discrepancy of information in a block, as detected by a checking code or technique. breakpoint. See: change in slope. bridge. (1) A network with a minimum o
28、f two ports or terminal pairs capable of being op- erated in such a manner that when power is fed into one port - by suitable adjustment of the elements in the network or the element connected to one or more other ports - zero output can be obtained at another port. Under these conditions the bridge
29、 is balanced. (2) An instrument or intermediate means in a measurement system that embodies all or part of a bridge circuit, and by means of which one or more of the electrical constants of a bridge may be measured. bridging connection. A parallel connection by means of which some of the signal ener
30、gy in a circuit may be withdrawn, frequently with imperceptible effect on the normal operation of the circuit. bridging gain. The ratio of the signal power a transducer delivers to its load ZB to the signal power dissipated in the main circuit load 2, across which the input transducer is bridged. br
31、idging loss. (1) The ratio of the signal power delivered to that part of the system following the bridging point, before the insertion of the bridging element to this signal power delivered to the same part after the bridging. (2) The ratio of the power dissipated in a load B across which the input
32、of a transducer delivers to its load A. NOTE: It is the inverse of bridging gain. Bridging loss is usually expressed in decibels. busy hour. The peak 60 min period during a 24 h period when the largest volume of com- munication traffic is handled. capacity. (1) The number of digits or char- acters i
33、n a machine word regularly handled in a computer. (2) The upper and lower limits of the num- bers which may be regularly handled in a computer. (3) The maximum number of binary digits which can be transmitted by a communica- tions channel in one second. carrier. (1) A wave having at least one char-
34、acteristic that may be varied from a known reference value by modulation. (2) That part of the modulated wave that corresponds in a specified manner to the unmodulated wave, having, for example, the carrier-frequency spectral components. NOTE: Examples of carriers are a sine wave and a recurring ser
35、ies of pulses. carrier frequency. (1) (periodic carrier). The reciprocal of its period. It is to be noted that 7 Authorized licensed use limited to: Tsinghua University Library. Downloaded on December 25,2010 at 11:02:05 UTC from IEEE Xplore. Restrictions apply. IEEE Std 599-1985 the frequency of a
36、periodic pulse carrier is often called the pulse repetition frequency in a signal transmission system. (2) (modulated amplifier). The frequency that is used to modulate the input signal for amplification. carrier group (base group). The frequency band, 60 kHz-108 kHz, containing twelve voice channel
37、s which serves as the basic build- ing block of a larger system. carrier modulation. A process whereby a high- frequency carrier wave is altered by a signal containing the information to be transmitted. carrier shift (frequency shift). The difference between the steady state, mark, and space frequen
38、cies in a system utilizing frequency shift modulation. carrier system. A communication system using frequency multiplexing to a number of chan- nels over a single path by modulating each channel upon a different carrier frequency and demodulating at the receiving point to restore the signals to thei
39、r original form. carrier-to-noise ratio. The ratio of the magni- tude of the carrier to that of the noise after selection and before any nonlinear process, such as amplitude limiting and detection. The bandwidth used for measurement of the noise should be specified when using this ratio. CCITT (Inte
40、rnational Consultative Committee for Telephone and Telegraph). An advisory committee established under the United Na- tions in accordance with International Tele- communications Convention (Geneva 1959), Article 13, to study and recommend solutions for questions on technical operation and tariffs. T
41、he organization is attempting to establish standards for intercountry operation on a worldwide basis. central office. The place where communica- tions common carriers terminate customer lines and locate the equipment which inter- connects those lines. It is usually the junction point between metalli
42、c pair and carrier system. central-office exchange. The place where a communication common carrier locates the equipment which interconnects incoming sub- scribers and circuits. channel (electric communication). (1) A single IEEE STANDARD DEFINITIONS OF POWER path for transmitting electric signals,
43、usually distinct from other parallel paths, or NOTE: The word path is to be interpreted in a broad sense to include separation by frequency division or time division. The term channel may signify either a one-way path, providing transmission in one direction only, or a two-way path, providing transm
44、ission in two directions. channel capacity (information theory). The maximum possible information rate through a channel subject to the constraints of that channel. NOTE: Channel capacity may be either per second or per symbol. channel group (group). A number of channels regarded as a unit. NOTE: Th
45、e term is especially used to designate part of a larger number of channels. channel supergroup (supergroup). A number of channel groups regarded as a unit. NOTE: The term is especially used to designate part of a larger number of channels. (2) A band of frequencies. character. One of a set of elemen
46、tary symbols which normally include both alpha and numeric codes, plus punctuation marks and any other symbol which may be read, stored, or written and is used for organization, control, or representation of data. character distortion. The normal and predict- able distortion of data bit produced by
47、char- acteristics of a given circuit at a particular transmission speed. character interval. In start-stop operation, the duration of a character expressed as the total number of unit intervals (including informa- tion, error checking and control bits, and the start and stop elements) required to tr
48、ansmit any given character in any given communica- tion system. characteristic impedance. (1) (two conductor transmission line for a traveling transverse electromagnetic wave). The ratio of the com- plex voltage between the conductors to the complex current on the conductors in the same transverse p
49、lane with the sign so chosen that the real part is positive. (2) (coaxial transmission line). The driving impedance of the forward traveling transverse electromagnetic wave. check before operate (checkback). A message Authorized licensed use limited to: Tsinghua University Library. Downloaded on December 25,2010 at 11:02:05 UTC from IEEE Xplore. Restrictions apply. SYSTEMS DATA TRANSMISSION AND RELATED CHANNEL TERMINOLOGY IEEE Std 599-1985 and control technique providing for confirma- tion of control request before operation. check summation (checksum). A redundant check is which groups of di