1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 1 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU30%#)&)#!4)/.3G0G0/&G0G03).!,).G0G03934%-G0G0.O G0 3).!,).G0G0$!4!G0G0,).+)45G134G0G0RecommendationG0G01 (Extract from the “LUEG0“OOK)NOTES1 ITU-T Recommendation Q.702 was published in Fascicle VI.7 of the Bl
2、ue Book. This file is an extract from theBlue Book. While the presentation and layout of the text might be slightly different from the Blue Book version, thecontents of the file are identical to the Blue Book version and copyright conditions remain unchanged (see below).2 In this Recommendation, the
3、 expression “Administration” is used for conciseness to indicate both atelecommunication administration and a recognized operating agency. ITU 1988, 1993All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic ormechanical, including phot
4、ocopying and microfilm, without permission in writing from the ITU.Fascicle VI.7 - Rec. Q.702 1Recommendation Q.702SIGNALLING DATA LINK1 General1.1 A signalling data link is a bidirectional transmission path for signalling, comprising two data channels operatingtogether in opposite directions at the
5、 same data rate. It constitutes the lowest functional level (level 1) in the SignallingSystem No. 7 functional hierarchy.1.2 Functional configuration of a signalling data link is shown in Figure 1/Q.702.1.3 A digital signalling data link is made up of digital transmission channels1)and digital switc
6、hes or theirterminating equipment providing an interface to signalling terminals. The digital transmission channels may be derivedfrom a digital multiplex signal at 1544, 2048 or 8448 kbit/s having a frame structure as defined inRecommendation G.704 1, or from digital multiplex streams having a fram
7、e structure specified for data circuits(Recommendations X.50 4, X.51 5, X.50 bis 6, X.51 bis 7).1.4 An analogue signalling data link is made up of voice-frequency analogue transmission channels either 4 kHz or3 kHz spaced, and modems.1.5 Signalling System No. 7 is capable of operating over both terr
8、estrial and satellite transmission links1).1)The terms transmission channel and transmission link are used in Signalling System No. 7 instead of transfer channel and transferlink used in Signalling System No. 6.2 Fascicle VI.7 - Rec. Q.7021.6 The operational signalling data link shall be exclusively
9、 dedicated to the use of a Signalling System No. 7signalling link between two signalling points. No other information should be carried by the same channel together withthe signalling information.1.7 Equipment such as echo suppressors, digital pads, or A/ law convertors attached to the transmission
10、link mustbe disabled in order to assure full duplex operation and bit integrity of the transmitted data stream.1.8 64-kbit/s digital signalling channels entering a digital exchange via a multiplex structure shall be switchable assemi-permanent channels in the exchange.2 Signalling bit rate2.1 Genera
11、l2.1.1 The standard bit rate on a digital bearer will be 64 kbit/s.Fascicle VI.7 - Rec. Q.702 32.1.2 Lower bit rates may be adopted for each application, taking into account the User Part requirements and thecapability of available transmission links.2.1.3 The minimum signalling bit rate for telepho
12、ne call control applications will be 4.8 kbit/s. For other applicationssuch as network management, bit rates lower than 4.8 kbit/s can also be used.2.2 Use of bit rates lower than 64 kbit/s2.2.1 For national telephone call control applications, use of Signalling System No. 7 at bit rates lower than
13、64 kbit/sshall take account of the requirement to minimize the answer signal delay when in-band line signalling systems areinvolved (Recommendation Q.27 8).2.2.2 Signalling System No. 7 can be used for direct international application at bit rates lower than 64 kbit/s betweencountries which have no
14、in-band line signalling systems in their national extension networks (see 2.1.3).2.2.3 The possible use of Signalling System No. 7 at bit rates lower than 64 kbit/s between countries which have in-band line signalling systems in their national extension networks is for further study.3 Error characte
15、ristics and availabilityError characteristics and availability requirements will conform to relevant Recommendations (for example,Recommendation G.821 9 on digital circuits). No additional characteristics or requirements will be specified in thisRecommendation.4 Interface specification points4.1 Int
16、erface requirements may be specified at one of three points, A, B or C in Figure 2/Q.702. The appropriatepoint depends on the nature of transmission links used and the approach toward the implementation of interfaceequipment adopted by each Administration.4.2 For the international application, inter
17、face requirements at either Point B or Point C will apply.4.3 Interface requirements for an international digital signalling data link will be specified at Point C in accordancewith the specific multiplex structure used (see 5.)4.4 Interface requirements for an international analogue signalling data
18、 link will be specified at Point B on a singlechannel basis, and thus are independent of multiplex equipment used. (See 6.)4.5 Interface at Point A may or may not appear in particular implementations, as each Administration may adoptdifferent approaches towards the implementation of interface equipm
19、ent. If it does appear in implementations, then theinterface requirements specified in Recommendations V.10 10, V.11 11, V.24 12, V.28 13, V.35 14, V.36 15,X.24 16 and G.703 17 (for 64-kbit/s interface) should be followed as appropriate.4.6 Implementations which do not follow all the requirements in
20、 the relevant Recommendations cited above shouldnevertheless take into account those requirements that are specified for testing and maintenance actions which requirecommunication between the two ends of a data link. Interface requirements for testing and maintenance are specified inRecommendation Q
21、.707.4 Fascicle VI.7 - Rec. Q.7025 Digital signalling data link5.1 Signalling data link derived from the 2048-kbit/s digital pathWhen a signalling data link is to be derived from a 2048-kbit/s digital path, the following shall apply:a) The interface requirements, specified at Point C in Figure 2/Q.7
22、02, should comply withRecommendations G.703 17 for the electrical characteristics and G.704 1 for the functionalcharacteristics, in particular the frame structure.b) The signalling bit rate shall be 64 kbit/s.c) The standard channel time slot for the use of a signalling data link is time slot 16. Wh
23、en time slot 16 is notavailable, any channel time slot available for 64-kbit/s user transmission may be used.d) No bit inversion is performed.5.2 Signalling data link derived from the 8448-kbit/s digital pathWhen a signalling data link is to be derived from a 8448-kbit/s digital link, the following
24、shall apply:a) The interface requirements, specified at Point C in Figure 2/Q.702, should comply withRecommendations G.703 23 for the electrical characteristics and G.704 1 for the functionalcharacteristics, in particular the frame structure.b) The signalling bit rate shall be 64 kbit/s.c) The stand
25、ard channel time slots for the use of a signalling data link are time slots 67 to 70 in descendingorder of priority. When they are not available, any channel time slot available for 64-kbit/s usertransmission may be used.d) No bit inversion is performed.Fascicle VI.7 - Rec. Q.702 55.3 Signalling dat
26、a link derived from the 1544-kbit/s digital path(For further study.)Note - When a signalling bit rate of 64 kbit/s is adopted, the values of bits should be inverted within thesignalling terminal or the interface equipment in order to meet the minimum mark density requirements of theRecommendation G.
27、733 2 based PCM systems.5.4 Signalling data link established over a digital path made up by digital sections based on different digitalhierarchiesWhen a signalling data link is to be established between networks based on different digital hierarchies andspeech encoding laws, the following shall appl
28、y:a) The interface requirements, specified at Point C in Figure 2/Q.702, should comply withRecommendations G.703 17 for the electrical characteristics and G.802 3 for other aspects, e.g., forinterworking arrangements.b) The signalling bit rate shall be 64 kbit/s.c) No bit inversion is performed.5.5
29、Signalling data link established over data circuitsWhen a signalling data link is to be established over data circuits derived from a 64-kbit/s digital stream havinga frame structure as specified in such Recommendations as X.50 10, X.51 11, X.50 bis 12 and X.51 bis 13 thefollowing shall apply:a) The
30、 interface requirements, specified at Point C in Figure 2/Q.702, should comply with relevantrequirements in one of the above-mentioned Recommendations, applicable to the environment of theintended use.b) When 64-kbit/s multiplexed streams are carried on 2048-kbit/s or 1544-kbit/s digital links,Recom
31、mendation G.704 1, should apply6 Analogue signalling data link6.1 Signalling bit rate6.1.1 Applications of the analogue signalling data link must take account of the delay requirements described in 2.2.6.1.2 For telephone call control applications, the signalling bit rate over an analogue signalling
32、 data link shall behigher or equal to 4.8 kbit/s.6.2 Interface requirementsIn case of 4.8-kbit/s operation, interface requirements specified at the interface point B in Figure 2/Q.702 shouldcomply with relevant requirements specified for 4.8-kbit/s modems in Recommendations V.27 18 and V.27 bis 19.
33、Inaddition, the following shall apply:a) Application of either Recommendations V.27 18 or V.27 bis 19 depends on the quality of the analoguetransmission channels used. Recommendation V.27 18 shall apply only to transmission channelsconforming to Recommendation M.1020 20, while Recommendation V.27 bi
34、s 19 to transmissionchannels conforming to Recommendation M.1020 20 or of lower quality.b) Full duplex operation over a 4-wire transmission link should be adopted.c) If a separate modem is to be used, the interface requirements specified in Recommendations V.10 10,V.11 11, V.24 12 and V.28 13, appli
35、cable at Point A in Figure 2/Q.702, should be followed as muchas possible.6 Fascicle VI.7 - Rec. Q.702References1 CCITT Recommendation Functional characteristics of interfaces associated with network nodes, Vol. III,Rec. G.704.2 CCITT Recommendation Characteristics of primary PCM multiplex equipment
36、 operating at 1544 kbit/s,Vol. III, Rec. G.733.3 CCITT Recommendation Interconnection of digital paths using different techniques, Vol. III, Rec. G.802.4 CCITT Recommendation Fundamental parameters of a multiplexing scheme for the international interfacebetween synchronous data networks, Vol. VIII,
37、Rec. X.50.5 CCITT Recommendation Fundamental parameters of a multiplexing scheme for the international interfacebetween synchronous data networks, Vol. VIII, Rec. X.51.6 CCITT Recommendation Fundamental parameters of a 48-kbit/s user data signalling rate transmission schemefor the international inte
38、rface between synchronous data networks, Vol. VIII, Rec. X.50 bis.7 CCITT Recommendation Fundamental parameters of a 48-kbit/s user data signalling rate transmission schemefor the international interface between synchronous data networks using 10-bit envelope structure, Vol. VIII,Rec. X.51 bis.8 CCI
39、TT Recommendation Transmission of the answer signal, Vol. VI, Rec. Q.27.9 CCITT Recommendation Error performance on an international digital connection forming part of anintegrated services digital network, Vol. III, Rec. G.821.10 CCITT Recommendation Electrical characteristics for unbalanced double
40、-current interchange circuits forgeneral use with integrated circuit equipment in the field of data communications, Vol. VIII, Rec. V.10.11 CCITT Recommendation Electrical characteristics for balanced double-current interchange circuits forgeneral use with integrated circuit equipment in the field o
41、f data communications, Vol. VIII, Rec. V.11.12 CCITT Recommendation List of definitions for interchange circuits between data-terminal equipment and datacircuit-terminating equipment, Vol. VIII, Rec. V.24.13 CCITT Recommendation Electrical characteristics for unbalanced double-current interchange ci
42、rcuits,Vol. VIII, Rec. V.28.14 CCITT Recommendation Data transmission at 48 kbit/s per second using 60-108 kHz group band circuits,Vol. VIII, Rec. V.35.15 CCITT Recommendation Modems for synchronous data transmission using 60-108 kHz group band circuits,Vol. VIII, Rec. V.36.16 CCITT Recommendation L
43、ist of definitions for interchange circuits between data terminal equipment (DTE)and data circuit-terminating equipment (DCE) on public data networks, Vol. VIII, Rec. X.24.17 CCITT Recommendation Physical/electrical characteristics of hierarchical digital interfaces, Vol. III,Rec. G.703.18 CCITT Rec
44、ommendation 4800 bit/s per second modems with manual equalizer standardized for use on leasedtelephone-type circuits, Vol. VIII, Rec. V.27.19 CCITT Recommendation 4800/2400 bit/s per second modem with automatic equalizer standardized for use onleased telephone-type circuits, Vol. VIII, Rec. V.27 bis.20 CCITT Recommendation Characteristics of special quality international leased circuits with special band-width conditioning, Vol. IV, Rec. M.1020.
