ITU-T G.341 (11 1988) (英) 1.3 MHz systems on stand

INTERNATIONALTELECOMMUNICATIONUNION)454'TELECOMMUNICATIONSTANDARDIZATIONSECTOROFITU).4%2.!4)/.!,!.!,/'5%#!22)%23934%-3).$)6)$5!,#(!2!#4%2)34)#3/&).4%2.!4)/.!,#!22)%24%,%0(/.%3934%-3/.-%4!,,)#,).%3-(Z3934%-3/.34!.$!2$):%$MM#/!8)!,#!,%0!)23)454Recommendation'(ExtractfromtheLUEOOK)NOTES1ITU-TRecommendationG.341waspublishedinFascicleIII.2oftheBlueBook.ThisfileisanextractfromtheBlueBook.WhilethepresentationandlayoutofthetextmightbeslightlydifferentfromtheBlueBookversion,thecontentsofthefileareidenticaltotheBlueBookversionandcopyrightconditionsremainunchanged(seebelow).2InthisRecommendation,theexpression“Administration”isusedforconcisenesstoindicatebothatelecommunicationadministrationandarecognizedoperatingagency.ITU1988,1993Allrightsreserved.Nopartofthispublicationmaybereproducedorutilizedinanyformorbyanymeans,electronicormechanical,includingphotocopyingandmicrofilm,withoutpermissioninwritingfromtheITU.FascicleIII.2-Rec.G.3411RecommendationG.341FascicleIII.2-Rec.G.3411.3MHzSYSTEMSONSTANDARDIZED1.2/4.4mmCOAXIALCABLEPAIRS(amendedatGeneva,1964;furtheramended)PreliminarynoteThepresentRecommendationdescribestwotypesofsystemsoncoaxialcablepairsproviding300telephonechannelsintheapproximatefrequencyband0.06to1.3MHz.Thelengthoftheelementarycablesectionisabout6kmforthefirsttypeofsystemandabout8kmforthesecond.Thefirstistobepreferredwhenitisplannedtoequipthecablewith6MHzrepeaterslateron,thesecondwhenitisplannedtoinstallsystemsbelongingtotheotherfamilyonthecablelateron,i.e.the4MHzsystem,12MHzsystemor18MHzsystem.1LinefrequenciesThesystemwillcarry300telephonychannels,transmittedtoline:-eitherbetween60kHzand1300kHzassupergroupsNos.1-5ofthe4MHzsystem(Figure1a)/G.341);-orbetween64kHzand1296kHzasamastergroupwitherectchannelsidebands(Figure1b)/G.341).FIGURE1/G.341Line-frequencyarrangementsforinternationalcarrier1.3-MHzsystemson1.2/4.4-mmcoaxialpair2Pilotsandadditionalmeasuringfrequencies2.1Line-regulatingpilotTheCCITTrecommendsthat1364kHzbeusedforthemainline-regulatingpilotonallregulated-linesections2FascicleIII.2-Rec.G.341crossingafrontier.Themainline-regulatingpilotisusedforautomaticcorrectionofcableattenuationwiththetemperature.Inanyregulated-linesectioncrossingafrontier,itisrecommendedthatinbothdirectionsoftransmissiontheAdministrationonthetransmittingsidepermanentlytransmitanauxiliaryline-regulatingpilotat60or308kHz,astheAdministrationonthereceivingsidemaychoose,soastoprovideforadditionalregulation,forexample.Thefrequencyaccuracyrecommendedforthepilotsis±1×10-5.Thepowerlevelofthesepilotsshouldbeadjustedattheoutputofthetransmitamplifiertohaveanominalvalueof-10dBm0.Theharmonicsofthe60and308kHzpilotsshouldeachhavealevelnothigherthan-70dBm0.ThetolerancesforthislevelarethesameasinRecommendationG.332,§2.1.Note-Somesystemsinuseemployapilotat-1.2Nm0.2.2Frequency-comparisonpilotsFornationalfrequencycomparison,itisrecommendedthata60or308kHzpilotbeused.Shouldinternationalfrequencycomparisonappeardesirable,theAdministrationsconcernedwillreachagreementonwhichofthesetwofrequenciestheywilluse.Thepowerlevelofafrequency-comparisonpilotshouldbeadjustedattheoutputofthetransmitamplifier,toanominalvalueof-10dBm0.Theharmonicsofthefrequency-comparisonpilotsshouldeachhavealevelnothigherthan-70dBm0.2.3AdditionalmeasuringfrequenciesFrequenciesthatcanbeusedasadditionalmeasuringfrequenciesareasfollows:-supergroupsNos.1to5frequencyallocation:(60),(308),556,808,1056,1304kHz;-mastergroupfrequencyallocation:(60),(308),804,1052,1304kHz.Note-Oneofthetwofrequenciesinbracketswillbeusedfortheauxiliaryline-regulatingpilot.Thepowerleveloftheseadditionalmeasuringfrequenciesshouldbeadjusted,attheoutputofthetransmitamplifier,tohaveanominalvalueof-10dBm0.Theharmonicsoftheadditionalmeasuringfrequenciesbelow650kHzshouldeachhavealevelatthispointnothigherthan-70dBm0.Note-Somesystemsinuseemployadditionalpilotsat-1.2Nm0.Theadditionalmeasuringfrequenciesshouldnotbepermanentlytransmitted.Theywillbetransmittedonlyforaslongasisnecessaryforactualmeasurementpurposes.3HypotheticalreferencecircuitTheCCITThasdefinedtwohypotheticalreferencecircuits,oneforsupergrouparrangementandtheotherformastergrouparrangement.Bothare2500kmlongandaredividedintoninehomogeneoussectionsof280kmeach.3.1Hypotheticalreferencecircuitusedinsupergrouparrangement1)Thishypotheticalreferencecircuit(seeFigure2/G.341)has,foreachdirectionoftransmission,atotalof:-threepairsofchannelmodulators,eachpairincludingtranslationfromtheaudio-frequencybandtothebasicgroupandviceversa;-sixpairsofgroupmodulators,eachpairincludingtranslationfromthebasicgrouptothebasicsupergroup_______________1)Thishypotheticalreferencecircuitisalsousedfor4MHzand6MHzsystemstransmittingsupergroupson1.2/4.4mmcoaxialpairsandforsystemsprovidingtwosupergroupsonsymmetricpairs.FascicleIII.2-Rec.G.3413andviceversa;-ninepairsofsupergroupmodulators,eachpairincludingtranslationfromthebasicsupergrouptothefrequencybandtransmittedonthecoaxialcableandviceversa.Itwillbeseenthatthereisatotalof18modulationsan