1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 1 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU30%#)&)#!4)/.3G0G0/&G0G03).!,).G0G03934%-G0G0.O G0 &5.#4)/.!,G0G0$%3#2)04)/.G0G0/&G0G04(%3).!,).G0G03934%-G0G0.O G0 G0G04%,%0(/.%53%2G0G00!24G0G0 450G9)45G134G0G0RecommendationG0G01 (Extract from the “LUEG0“O
2、OK)NOTES1 ITU-T Recommendation Q.721 was published in Fascicle VI.8 of the Blue Book. This file is an extract fromthe Blue 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 co
3、pyright conditions remain unchanged (see below).2 In this Recommendation, the 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
4、utilized in any form or by any means, electronic ormechanical, including photocopying and microfilm, without permission in writing from the ITU.Fascicle VI.8 - Rec. Q.721 1Recommendation Q.721Fascicle VI.8 - Rec. Q.721FUNCTIONAL DESCRIPTION OF THE SIGNALLING SYSTEM No. 7TELEPHONE USER PART (TUP)1 Ge
5、neralUse of Signalling System No. 7 for telephone call control signalling requires:- application of Telephone User Part (TUP) functions, in combination with- application of an appropriate set of Message Transfer Part (MTP) functions.A general description of the signalling system and the division of
6、functions between the Message Transfer Partand the Telephone User Part are presented in Recommendation Q.700 and the requirements of interaction betweenthose two parts are contained in Recommendation Q.701.2 Telephone User PartThe Telephone User Part specified in these specifications defines the nec
7、essary telephone signalling functionsfor use of Signalling System No. 7 for international telephone call control signalling. It is specified with the aim ofproviding the same features for telephone signalling as other CCITT telephone signalling systems.Signalling System No. 7 can be used to control
8、the switching of all types of international circuits to be used ina worldwide connection, including circuits with speech interpolation and satellite circuits.The system meets all requirements defined by the CCITT concerning the service features for worldwideinternational semiautomatic and automatic
9、telephone traffic. It is designed for the bothway operation of speech circuits.When used with homogeneous digital telephone circuits the continuity of these circuits is ensured by themeans for transmission quality supervision and failure detection that are inherent in the digital systems providing t
10、hesecircuits. However, the system includes means for link-by-link assurance of continuity check of the speech path whenused with analogue telephone circuits and/or digital circuits including certain types of equipment, where faultindications are lost, e.g., circuit multiplication equipment.The signa
11、lling system is suitable for national telephone applications. Most telephone signalling message typesand signals specified for international use are also required in typical national applications. In addition to these,national applications typically require additional signalling message types and si
12、gnals, the system provides ample sparecapacity for such additions.The standard label structure specified for telephone signalling messages requires that all exchanges using thesignalling system are allocated codes from code plans established for the purpose of unambiguous identification ofsignalling
13、 points. The principles to apply to the international signalling network are specified inRecommendation Q.708.3 Message Transfer PartThe Message Transfer Part of Signalling System No. 7 is specified in Recommendations Q.701 to Q.709. Anoverview description of the Message Transfer Part is contained i
14、n Recommendation Q.701.The Message Transfer Part defines a range of functions by which different signalling modes and differentsignalling network configurations may be realized. Any application of Signalling System No. 7 requires that anappropriate selection of these functions is applied depending on the intended use of the system and the characteristicsof the telecommunications network concerned.
