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1、INTERNATIONALTELECOMMUNICATIONUNIONITU-TSupplement2TELECOMMUNICATION(SeriesE)STANDARDIZATIONSECTOROFITU(01/94)TELEPHONENETWORKANDISDNOPERATION,NUMBERING,ROUTINGANDMOBILESERVICEVARIOUSTONESUSEDINNATIONALNETWORKSSupplement2(toITU-TRecommendationE.180)FOREWORDTheITUTelecommunicationStandardizationSe
2、ctor(ITU-T)isapermanentorganoftheInternationalTelecom-municationUnion.TheITU-Tisresponsibleforstudyingtechnical,operatingandtariffquestionsandissuingRecommendationsonthemwithaviewtostandardizingtelecommunicationsonaworldwidebasis.TheWorldTelecommunicationStandardizationConference(WTSC),whichmeets
3、everyfouryears,establishedthetopicsforstudybytheITU-TStudyGroupswhich,intheirturn,produceRecommendationsonthesetopics.Supplement2wasrevisedbytheITU-TStudyGroup1(1993-1996)andwasapprovedundertheprovisionsofWTSC-93ResolutionNo.5byStudyGroup1atitsmeeting18-28January1994.Thisisthefirstrevisionofthiss
4、upplementundertakensince1980.___________________NOTES1AsaconsequenceofareformprocesswithintheInternationalTelecommunicationUnion(ITU),theCCITTceasedtoexistasof28February1993.Initsplace,theITUTelecommunicationStandardizationSector(ITU-T)wascreatedasof1March1993.Similarly,inthisreformprocess,theCCI
5、RandtheIFRBhavebeenreplacedbytheRadiocommunicationSector.InordernottodelaypublicationofthisRecommendation,nochangehasbeenmadeinthetexttoreferencescontainingtheacronyms“CCITT,CCIRorIFRB”ortheirassociatedentitiessuchasPlenaryAssembly,Secretariat,etc.FutureeditionsofthisRecommendationwillcontainthep
6、roperterminologyrelatedtothenewITUstructure.2InthisRecommendation,theexpression“Administration”isusedforconcisenesstoindicatebothatelecommunicationadministrationandarecognizedoperatingagency.ITU1994Allrightsreserved.Nopartofthispublicationmaybereproducedorutilizedinanyformorbyanymeans,electronic
7、ormechanical,includingphotocopyingandmicrofilm,withoutpermissioninwritingfromtheITU.Supplement2Supplement2–SeriesE(01/94)VARIOUSTONESUSEDINNATIONALNETWORKSTONEFREQUENCY(Hz)CADENCE(Seconds)ALBANIADIALTONE425CONTINUOUSRI