ITU-T G.172 (11 1988) (英) Transmission plan aspects……

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1、INTERNATIONALTELECOMMUNICATIONUNION)45 4'TELECOMMUNICATIONSTANDARDIZATIONSECTOROFITU42!.3-)33)/.3934%-3!.$-%$)!42!.3-)33)/.0,!.!30%#43/&30%#)!,#)2#5)43!.$#/..%#4)/.353).'4(%).4%2.!4)/.!,4%,%0(/.%#/..%#4)/..%47/2+42!.3-)33)/.0,!.!30%#43/&).4%2.!4)/.!,#/.&%2%.#%

2、#!,,3)45 4Recommendation'(Extractfromthe"LUE"OOK)NOTES1ITU-TRecommendationG.172waspublishedinFascicleIII.1oftheBlueBook.ThisfileisanextractfromtheBlueBook.WhilethepresentationandlayoutofthetextmightbeslightlydifferentfromtheBlueBookversion,thecontentsofthefileareidenticaltotheBlueBookver

3、sionandcopyrightconditionsremainunchanged(seebelow).2InthisRecommendation,theexpression“Administration”isusedforconcisenesstoindicatebothatelecommunicationadministrationandarecognizedoperatingagency.ãITU1988,1993Allrightsreserved.Nopartofthispublicationmaybereproducedorutilizedinanyformorbyanymean

4、s,electronicormechanical,includingphotocopyingandmicrofilm,withoutpermissioninwritingfromtheITU.RecommendationG.172FascicleIII.1-Rec.G.172TRANSMISSIONPLANASPECTSOFINTERNATIONALCONFERENCECALLS(Malaga-Torremolinos,1984;amendedatMelbourne,1988)Thetransmissionconsiderationsgivenhereareapplicabletoconf

5、erencecallssetupandoperatedinaccordancewithRecommendationE.151.1InordertorespectCCITTRecommendationsconcerningloudnessratingsoninternationalconnections,highqualitybridgingequipmentshallbeused.Thisequipmentshallbedesignedtoprovideanominaltransmissionlossof0dBinthedirectionfromwhicheverparticipantis

6、forthemomentactive(speaking)toallinactive(listening)participants.Thislossshallbemeasuredbetweenequallevelswitchingpointsofnationalcircuitsorvirtualswitchingpointsofinternationalcircuits.Note-Someconferencebridgesemploytheuseofautomaticgaincontrol(AGC)tominimizethecontrastthatexistsbetweenthespeech

7、levelsofparticipantsonconnectionshavingdifferentlosses,andtheaboveconsiderationdoesnotapplyforsuchbridges.ThetransmissionconsiderationforbridgeswithAGCisasubjectforfuturestudy.2Amodernconferencebridgeshallbeusedw