1、I N T E R N AT IO N A L STANDARD ISOIIEC 7480 Second edition 1991 - 12-1 5 (Reaffirmed 2004) Information technology - Telecommunications and information exchange between systems - Start-stop transmission signal quality at DTE/DCE interfaces Technologies de linformation - TcY6cornmuriications et echa
2、uge dinformafion entre sysf Pmes - Qualite des signaux de transmissicn aryl hrnique a IIX in t wfac es E TTDIETCD National Standard of Canada CAN/CSA -ISO/IE C-7480-95 International Standard ISO/IEC 7480:1991 has been adopt e d, without m odif ication, as CAN/CSA-ISO/IEC- 7480-95, which has been app
3、roved as a National Standard of Canada by the Standards Council of Canada. February 1995 Reference number ISOilEC 7480: 1991 (E) EOllEC 748O:1991 (E) Foreword IS0 (the International Organization for Standardization) and 1EC (the International Electrotechnical Commission) form the specialized system
4、for worldwide standardization. National bodies that are members of IS0 or IEC participate in the development of International Standards through technical committees established by the respective org2nization lo deal with particular fields of technical activity. IS0 and IEC technical corn- mittees co
5、llaborate in fields of mutual interest. Other international or- ganizations, governmental and non-governmental, in liaison with IS0 and IEC, also take part in the work. In the field of information technology, IS0 and IEC have established a joint technical committee, ISO/IEC JTC 1. Draft Internationa
6、l Standards adopted by the joint technical committee are circutated to national bod- ies for voting. Publication as an International Standard requires ap- proval by at least 75 Oh of the national bodies casting a vole. International Standard ISOAEC 7480 was prepared by Joint Technical Committee ISO/
7、IEC JTC 1, lnforrnation technology. This second edition cancels and replaces the first edition (IS0 7480:1984), of which it constitutes a technical revision. Annex A of this international Standard is for information only. 0 !SO/IEC 1991 All rights reserved. No part of this publication may be reprodu
8、ced or utitized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permlssion in writing from the publisher. Printed in Switzerland ISO/IEC Copyright Office Case Postale 56 CH-1211 Geneve 20 * Switzerland ii ISOllEC 7480:1991 (E) Introduction The int
9、ent of this International Standard is to complement the eleclt-ical characteristics specified in CCITT V-series reconirnendations, and to provide a measurement for the transmission signal quality charac- teristics not covered in those docriments The signal quality requirement that start-stop transmi
10、ssion equipment should meet is in par-t dependent on the application and in part de- pendent on the mechanism for timing derivation used by the equipment. For early start-stop transmission equipment. timing was derived or controlled from a mechanical source but nowadays an electronic source is commo
11、nplace. An additional factor is that, whereas most sfart-stop transmissic-in cay- ries the timing information inherently within the signalling between the transmitting equipment and the receiving equipment, start-stop equip- ment may interface to a converter which encodes the information within a sy
12、nchronous transmission system in which case, the requii-ed signal quality at the interface to the converter may need to be miore tightly control led. To cover both types of equipment in both types of application. the signal quality specification in this International Standard is given separalely Tor
13、 four performance categories, two of which (PI and P2) are intended ai- DTEs using mechanical timing) and two for DTEs using electronic lim- ing. 8y having two mechanical categories, early start-stop transmission equipment with very limited signal quality capability is accomniodated (Category PI). F
14、or the two electronic categories. the more stringent (Category IT) is for equipment to be connected to synchronous DCEs operating in asynchronous mode in accordance with CClTT Rec- ommendation V.14. For each of the four- categories defined for the transmitting elements of DTEs (I, II, PI and P2), fo
15、ur cornplernentary categories are defined for the receiving elements of DTEs (A, 8. PA. PB). Notwit h sta nd i ti g the obvious pairings implied by the coin plem c! ti t a ry categories, the intention is that any receiving equipment may operate with any transmitting equipment, the actual selection b
16、eing dependent on such factors as channel characteristics and economic considerations of the dala comrnrinication system 7he importance of this International Standard is particularly evident when the transmifting arid receiving equipments are furnished by different organizations as it provides a bas
17、is for agreement between the parties involved. 1) It is intended to delete the mechanical categories at the next revision (see footnote 2 to table 1. At that time, consideration will be given to amending the electronic timing definition by replacing “a signal“ in the first line by “an isochronous si
18、gnal“ and amending the other definitions accordingly. iii -I_-_ . INTERNATIONAL STANDARD ISOllEC 7480:199?(E) Information technology - Telecommunications and information exchange between systems - Start-stop transmission signal quality at DTElDCE interfaces I Scope 1.1 This International Standard sp
19、ecifies signal quality requirements for serial data transmission at the interface between s ta rt-s top Iran s rn is s ion Data Terminal Equipment (DTE) and Data Circuit- terminating Equipment (DCE). The interface referred to in lhis International Standard conforms to CCITT Recommendations V 24 (tel
20、ephone networks) and X.24 (dala networks) as specified in DCEs of the fol- lowing CC1TT Recommendations: - V.21, V.22, V.22 bis, V.23, V.26 ter, V.32, V.32 bis, X.20. X.20 bis together with V.28 electrical characteristics; .- X.20 together with V.40 and/or V.ll electrical characteristics. The signal
21、 quality requirement is limited to start- stop transmission at the interface with asynchro- nous DCEs. or wilh synchronous DCEs operating in asynchronous mode in accordance with CCiTT Rec- ommendations V.14 or V.42. Signal quality pertaining to DTEs working in a synchronous mode of operation is not
22、part of this lnternational Standard. This International Standard is also applicable when the interface as specified in the above CCITT Rec- ommendations is provided at the ISDN Reference point R as defined in CClTf Recommendation 1.411 and as specified in CCITT Recommendations V.110, V.120 and X.30.
23、 1.2 The signal quality characteristics appIy re- gardless of whether or not multiplexing equipment is included. They do not apply where there is inter- mediate equipment and no signal regeneration is p ravi d ed between i n t erco n ne ct ed sect ions . 1.3 This International Standard does not desc
24、ribe the signal quality of the DCE or the line associated with it. Neither does it describe any requirement for an acceptable bit error rate. 1.4 This lnternational Standard does not specify the speed characteristics. The nominal value of the modulation rate and the character interval are ap- plicat
25、ion dependent. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publi- cation, the editions indicated were valid. All stan- dards are subject to revision, and patties lo agree
26、ments based on this International Standard are encouraged to investigate the possibility of ap- plying the most recent editions of the standards in- dicated below. Members of IEC and IS0 maintain registers of currently valid International Standards. CCITT Recornmendation 1.41 1:1988, lSDN user- r7 e
27、 t w o r k in t erfa c es - Reference c on figuration s. CClTT Recommendation V.10 (= X.26):1988. Elec- trical characteristics for unbalanced doobie-curr-ent interchange circuits Tor general use with inlegraled circuit eqriipmenf in the field of data cornmuni- cations. CCITT Recommendation V 1q (=I
28、X.27).7988 Elec- f rica I c /? a ra G f e ris tic s for b a I a n c ed do ub I e-c LUW t interchange circuits for ger7eral use with ir7fegr-aled circuif eqnipmenf in the field of data commnr7i- calians. CClTT Recommendation V. 14.1988, Transmission of sfart-stop characteJ-s over SYC/J/-OMIUS hearer
29、clian- nels. 1 ISO/IEC 7480:1991 (E) CCITT Recommendation V.21:1988, 300 bits per sec- ond duplex modem standardized for use in fhe gem era/ switched telephone network. CCITT Recommendation V.22:1988, 1200 bils per second duplex modem standardized for use in ilie general switched telephone network a
30、nd on point- fo-point 2-wire /eased felephone-type circuits. CCITT Recommendation V.22 bis:1988, 2400 hits per second duplex modern using the frequency division technique standardized for use on fhe general switched telephone network and on poii7f-f 0-point 2-wire leased telephone-type circuits. CCt
31、TT Recommendation V.23:1988, 600/1200 baud modem standardized for use in the genei-a/ switched telephone network. CCITT Recommendation V.24:7988, Lisf of definitions for inferchange circuits between data terminal equipmenl and data cir-cuit-terrninafing eqiiipmenf. CCITT Recornmendation V.26 ter:198
32、8, 2400 hits per second duplex modern using the echo cancellation technique standardized for use on !he general swifched telephone network arid on point-lo-poinf 2-wire leased feiephone-type circuits. CCITT Recommendation V.28:1988, Electrical characteristics for unbalanced double-cut-renf irifer- c
33、hange circuifs. CCITT Recornrnendatiori V.32:1988, A family of 2-wire, duplex modems operating at dafa signalling rafes of up fo 9600 bifls for use on the general switched telephone network and on leased telephone-lype circuits. CCITT Recommendation V.32 bis:l990. A duplex modern operating af data s
34、ignallirig rates of rip fo 14400 bills for use on the general swilched tele- phone network and on leased point-io-poini 2-wire telephoue-type circuits. CCITT R ecum rn e n d at i on V. 42 : 1 9 8 8, rror-correcting procedures for DCEs using asynchronous-to- sync h r o n o us c n n v e r.s i o n . CC
35、lTT Recornmendation V.110:7988, Sopport of dafa terminal equipments (DTEs) wit17 V-series type inter- faces by an integrafea services digital network (ISDN). CCITT Recommendation V.120:?988, Supporf by an lSDM of data terminal equipment will7 V-series type interfaces with provision for statistical r
36、niilfiplexing. CCITT Recomm e ndatiori X.20: 1988, Inf erfaace be- tween dafa terminal equipment (DTE) and data circuif-terminating equipment (DCE) for start-stop transmission services on public data networks. CCITT Recommendation X.20 bis: 1988, Use on public data nefworks of dafa terminal equipmen
37、t (5T.E) which is designed for interfacing fo asynchronous duplex V-series modenis. CCITT Recommendation X 24: 1988, List of definitions for interchange circriifs betweeri data terminal equipmet7f (DE) arid data circLiit-leT(77jiiafjiia equip- ment (DCE) on public dafa networks. CCITT Recommendation
38、 X.30:1988, Support of X.21. X.21 bis arid X.20 bis based data terrnina! equip rnenfs (DTEs) hy an iniegrafed services digilal net- work (ISDN). 3 Definitions For the pur-poses of this International Standard, the fdlowing d efi n i ti on s a p p I y . 3.1 electronic timing: An irnplementalion in whi
39、ch a signal serves to determine the duration of signal elements and to achieve synchronizalion within a transmission system. and is derived from an elec- tronic circuit. 3.2 mechanical timing: An impfernenfalion in which a signal serves to determine the duration of Fignal elements and fo achieve syn
40、chroniration within .r7 tr ansmissiori system, and is generally derived frrm the angular velocity of an electric motor (power Ti-e- quency used as timing source is also included in his c a t F! g Q r y ) 3.3 start-stop system: Data transmission system in which each signal representing a character is
41、 pre- ceded by a start qignal which wrves to prepare ihe receiving device for the reception of a character signaf arid registration of a character, and is fol- lowed by a stop signal which serves to prepare fhe receiving device for- the reception of a suhsequenl start signal 3.4 start-stop transmiss
42、ion: Asynchronous trans- mission such that each group of signals repi-eseni- ing a character is preceded by a start signal and is followed by a stop signal. 3.5 continuous start-stop operation: Method of op- eration in start-stop transmission in which Ihe signals represenfing a series of characters
43、follow one another conliguously. 3.6 signal element: Each of the parts constituling a telegraph or data signal and distinguished from the others by its nature, magnitude, duration and rela- live position (or by one or some of lhese features only). 2 ISOIIEC 7480:1991(E) 3.7 unit intervaf: In a syste
44、m using an equal length code, or in a system using an isochronous rnodu- lation, the interval of time such that the theoretical durations of the significant intervals of a telegraph modulation (or restitulion) are whole multiples of this interval. 3.8 modulation rate: Reciprocal of the tinit interva
45、l measured in seconds. This rate is expressed in baud. 3.9 character interval: The duration of a character expressed as the total number of unit intervals (in- cluding information and parity check) plus the start and stop signals. 3.10 start signal: In start-stop transmission. a sig- nal at the begi
46、nning of a character that prepares the receiving device for the reception of the code ef- em P tits. NOTE 1 generally having the duration of a unit interval A start signal is limited to one signal element 3.11 start transition: In a character transmitted in a start-stop system, the mark-to-space tra
47、nsition at the beginning of the start signal. 3.12 stop signal: In start-stop transmission. a signal at the end of a character that prepares the receiving device for the reception of a subsequent character. NOTE 2 A stop signal is usually limited to one signal elernent having any duration equal to o
48、r greater than a specified minimum value. 3.13 degree of start-stop distortion (1) Ratio to the unit interval of the maximum measured difference, irrespective of sign, between the actual and theoretical intervals separating any significant instant of modulation (or of restitution) from the significa
49、nt instant of the statt element iim- mediately preceding it. (2) The highest absolute value of individual dis- tortion affecting the significant inslants of a start- stop modulation. The degree of distortion of a start-stop modulalion (or restitution) is usually expressed as a percentage. NOTES 3 The result of the measurement should be completed by an indication of the period, usually limited, of the ob- servation 4 Distinction can be made between the degree of late (or positive) distortion and the degree of early (or negative) distortion. 5 The theoretical intervals are relat
