AsysmMetricalcableIsmadeofSeveralPairsOfDoubleConductorsCalledCorewiresinaprotectivePochva.INorderToredoreducetheinterferenceBeenthepairsOfwires, everyPairofwireSismadeItToatwistedshape, který jako řídkátwistedwire.TwistedpairwiresaretWocopperwireswithadiateRof0.32 mm ~ 0.8 mm, kteréeretwistedAfterinsulationAndotherprocesses.OniaderividedIntounShieldwwistedpair (UTP) ashieldtwistedpair (SHIELDEDTWistedpair, STP) Twokinds.VícepairsoftWistedPairsIntoacableaReSymmetricalCables.TheCorewireofThesymMetricalCableistHinthantheopenwire, bezadiaterof0.4 mm ~ 1.4 mm, soitslossisslargerthatoftheopenwire, buttheperformanceismorestable.SymmetricalCablesEwidelyusedsForUseraccessCircuitsInSiredTelephoneNetworks.Theamplitude-frequencycharacteristicsofsymmetricalcablesareoflow-passtype,andthecrosstalkincreasesasthefrequencyrises,sothedegreeofmultiplexingisnothigh.
Definice
SymetricalCable: ConsistsoftWowowireswiththesamequality, WireDiaMiaMeterAndinsinsulationResistancetoground, a isuladwiresformformapairoftransmisionloops, acommunicable formoredbytwistingMultiplepairsOfsuchwires..
Čínský název: Symetrický kabel
Název cizího názvu: Symetricalcable
Alternativename: Žádné
Předmět aplikace: Informační komunikace
Funkce: SameresistanceToground, TwoIdenticalwires, TransmismissioLoop, kroucení
TwoIDICICICICALWIRESARETWistedTogetherFommunication.Itseemsthatthhishasbecomeasmetricalcable, butthingsarenotthathimple.Obrázek 1ShowsapictureofasymmetricalCableForOfficeuse.WewillinntroducethestructureofsymMetricalcableAgain:
Obrázek 1SymetricalCableforlocaluse
Izolace
TheconductorsinSymMetricalCablesgenerallyuseCopperwires, swireDiaMeterof0.25 mmto1.4 mm.ThediaMeterofThesymmetricalCableuseDenthecityisusUsUsUsUSuly0.4 mm～0.9 mm; thediaMeterofThesymMmetricalCableusedForthelongDistanceisusUsually1.2 mm.Inafewcases, symetricalcAblesWithalumininumcoresalsoappear.
AsfortheinsulationMaterialsofsymMetricalCables, oniaderividedIndotheFollingThreetecategories:
1) Papír: Papír-izolovaný kabel Shavethreeforms: papírový sáček, Pulpandrope.THEETHODOFROPEINSULULULULIONISTOWINDTHEROPEINASPIRALONTHEWIRE, ATHENWRAPITWITH1TO2LAYERSOFPAPERTAPE.
2) Polyvinylchlorid: theDielectricConstantAntDielectriclossofPolyninylchloridearelativelativelarge, soitiseLitedtoshort-distancesYmetricalcakbles.Avšak TheCableofThishaterialhasflame-RetardantPropertiesandCanbeusedForindoorwiring.
3) PolyoleFinandpolystyren: TheSetWomaterialsHavegoodhigh-Frequencyperformance, andarecomMoNlyuseuseuseuseuseuseuseuseuseuseusedIncablestHattransMitSIGNALTHEMegahertzlelorbelowtheterTiaryGroup.PolystyreneisussuallymadeByrope.Apolyolefins nejvíce.
INORDERTOFACILITATEIDITIFIKACE, odlišená liningulaysUssuallyChooseosedferentColors.
StrandingMethod
V „komunikaci“ TheConceptofStar-TwistingwasmentionintheintroduktionOfterminology aheresiSabriefieFierifinntroductionTothedifferentTwistingMethods.
1) 2OR4InsulatedWireSaretWistedIntoa2-Wiregroupora4-WireGroupwithanappropriaTetWist.Forra4-wiregroup, kdykoli se vyskytl, whenshepositionSofthe4wiresaresquare, wecallitastar-quad4-wiregroup, inwhichthe2wireSonthediagonalformaloopoopoopoopoopoopoopoopoopoopoopoopoopoopoopoopoopoop.
2) The4wiresthataretWistedInTotwo2-WireGroupsFirst, a antrentwistedToeachther, Wecallitadouble-Pairtwisted4-Wiregroup.
3) Vrstvové řetězce: TwistSeveralwiregroupsIntoAcablecoreInlayers.
4) UNITTYPE: FirsttWistSeralwiregroupsIntoIntependendentUnits, a antrentwistSeveralunitInTocablecoress.
OnTheoutsideofTheLinegroup, odlišný ColortieMarkSareFenUsedStodistingIfferentLinegroups.
Pochva
INordertoensuretheSafetyofSyMmetricalcAbles, WraptapeOnTheoutsideofTheCableCore, asometimesAddashieldingLayerandasheath.
1) Papír-izolaci a izolaciPolyRyrenerope-tapeinsulatedCablesRequiretheuseofAsealedsheath.V přípravě, olově-seeledsheathswereused, Andlater, hliník-seeledsheathswerealsoused.Inmecázy, analumininum-polyethylenbondedsheathisalsosed, který má -semi-hermeticsheath.
2) Forendoorcables, PochvasMadeofpolyninylchlorideorlowhalogen (bez orhalogenu) materiály používané.
OnTheoutsideofThePochva, podle toho, podle toho, co je diferenciérsheathsneedDedToEnSuretheSafetyoftHecommunication.
Snížit rušení
InThedeSignandManufactureofsymMetricalcAbles, ScientificAndTechnologicalworkershavetakenvariousMeasures, butthewireloopthererewillStIllBeaCiveDegreeOfMutualInterferenceInterferences.INORDERTOREDUCECHEIMPACTOFNEAR-ENDCROSSTALKBETNETINELOOPOOPSONTRANSMISISELiNISIFFERENTDIRECTIONS, ScientistshavetHethothingotherothothethods:
1) DualCableSystem: TwoloopsTatarenotintheSameCavethethefRequencyfortWo-Waytransmision.
2) SingleCableSystem: OutEonelooPoopisesfortWo-waytransmisionSatifferentFrequency.
3) Innershield: Někdy asspecialshieldisusedSoseparateTeCoreCoreTotWopartSinaCableToreplacetwokables.WecallthistypeofCableaninnershieldCable.