思科VOIP语音技术培训02CVO

Chapter2:

IntroductiontoAnalogTelephony2-1Copyright©1998,CiscoSystems,Inc.ObjectivesUponcompletionofthischapter,youwillbeabletoperformthefollowingtasks:Givenananalogtelephonynetwork,identifytheroleofeachcomponentwithinthenetwork.Thecomponentsaretelephones,lines,loops,switches,andtrunks.Givenananalogtelephonynetwork,describethetelephonysignalingonlinesandtrunksGivenatelephonynetwork,tracethepathofatelephonecallTelephoneCallComponents2-3Copyright©1998,CiscoSystems,Inc.TelephoneCallComponentsTelephoneLocalloopVoiceswitchCO(centraloffice)PBX(privatebranchexchange)TrunksTelephoneComponents2-5Copyright©1998,CiscoSystems,Inc.Handset(receiverandtransmitter)SwitchhookHybrid(2-to-4wireconverter)SidetoneDialerRingerTelephoneComponentsTelephone

CompanySwitchTelephone2-WireLocalLoopRingerSwitchHookLoopLengthComp.Dialing(PulseorTone)BalanceNetwork2-Wire4-WireHybridReceiverTransmitterTelephoneSignaling2-7Copyright©1998,CiscoSystems,Inc.TelephoneSignalingSupervisorysignalingReleaseconnection(on-hook)Requestforservice(off-hook)RingingAddressing(dialeddigits)PulseDTMFOn-HookTelephoneSwitchLocalLoopLocalLoop-48DCVoltage(Battery)DCOpenCircuitNoCurrentFlowHandsetoncradle

andswitchhookisopenLocalLoopLocalLoopOff-HookClosedCircuitDCCurrentDialToneTelephoneSwitchOff-HookRingingLocalLoopLocalLoopOff-HookClosedCircuitRing-BackToneDCCurrentRingingVoltageTelephoneSwitchRinging(cont.)UnitedStates

Cadence

Europe

Cadence

0.40.40.22Sec2Sec4SecPulseMake(CircuitClosed)Break(CircuitOpen)Off-HookDialingInterdigitNextDigitPulsePeriod50ms—20pulsespersecond

100ms—10pulsespersecondUS:60/40Break/Make700msDualToneMultifrequencyDTMF123456789*0#120913361477697770852941Timing:60msBreak40msMakeInformationalSignaling—CallProgressIndicators(UnitedStates)ToneFrequency(Hz)OnTime(sec)OffTime(sec)DialBusyRing-back,lineRing-back,PBXCongestion(toll)Reorder(local)Receiveroff-hookNosuchnumber

Confirmationtone350+440480+620440+480440+480480+620480+6201400+2060+2450+2600200to400Continuous0.5 0.52 41 30.2 0.30.3 0.20.1 0.1Continuous,Freq.Mod1HzLocalLoops2-16Copyright©1998,CiscoSystems,Inc.TelephoneCompanySwitchLocalLoopLocalLoopLocalLoopsAloopisthephysicalpairofwiresfromthesubscribertothetelephonecompanyswitchVoiceSwitches2-18Copyright©1998,CiscoSystems,Inc.VoiceSwitchesTelephoneCompanyPBXCOIntermediatePBXCOCOCentralOfficeSwitchAllprivatephonesaredirectlyconnectedtoaCOswitchTwo-wireconnectiontoindividualanalogphonesCallstakeoneofthefollowingpathsSwitchedwithintheCOSenttoanotherCOSenttoanintermediateswitch(scalability)IntermediateSwitchSwitchcallsbetweenswitchesConnectstrunks100090008000300070002000PrivateBranchExchangeUsedinprivatesectorRemotebranchsubsystemSwitches(eXchanges)callslocallyKeeps“local〞callsoffpublicnetworkFewertrunkstoCOPrivatelinebetweenPBXsTrunks2-23Copyright©1998,CiscoSystems,Inc.TrunksTelephoneCompanyPBXPBXCOCOTrunkInterofficeTrunkCOCOCOTrunkPrivate

TrunkLineInterofficeTrunkIntermediateForeignExchangeTrunksForeignexchangeofficePlugsdirectlyintothelinesideofaswitchActslikeaphone/switch,thinksitisaphoneForeignexchangestationSitsattheremotesiteActslikeaswitch/phone,thinksitisaswitchDID/DODTrunksTelephoneCompanyPBXCODIDYouhaveacallTelephoneCompanyPBXCODOD9527-XXXXTrunkSignaling2-27Copyright©1998,CiscoSystems,Inc.Trunk/LineSeizureSignalingTypesCOtophone/FXO/FXSLoopstartGroundstartPBXtoPBXE&MTypeItoVStartsignaling Winkstart Immediatestart Delaystart

LoopStartSignalingCOorFXSModuleTelephone,PBX,orFXOModule.RingGen.-48VDCBatteryCOorFXSModuleTelephone,PBX,orFXOModule.RingGen.-48VDCBatteryIdleState(On-Hook):TelephoneorPBXhasopen2-wireloop.COorFXSmodulehasbatteryonring,groundontip.PBXSeizure(Off-Hook):TelephoneorPBXcloses2-wireloop.COorFXSmoduledetectscurrent.COwillreturndialtone.TipRingTipRingLoopStartSignaling(cont.)COSeizure:COappliesACringvoltage,superimposedoverthe-48VDC.Whenphonegoesoff-hook,COremovesringvoltageandcompletescircuit.COorFXSModuleTelephone,PBX,orFXOModuleRingGen.-48VDCBatteryTipRingCOorFXSModuleTelephone,PBX,orFXOModuleRingGen.-48VDCBatteryTipRingGroundStartSignalingIdleState(On-Hook):PBX/FXOmonitorstipforground.BatteryfromCO/FXSappearsonringlead.COorFXSModulePBXorFXOModuleRingGen.-48VDCBatteryTipGroundDetectorTipRingPBXSeizure:PBX/FXOsensestipgroundfromCO/FXS,closesthe2-wireloop,and

removesringground.COorFXSModulePBXorFXOModuleRingGen.-48VDCBatteryTipGroundDetectorTipRingPBXSeizure:PBX/FXOgroundsringlead.CO/FXSsensesringgroundandthengroundstiplead.COorFXSModulePBXorFXOModuleRingGen.-48VDCBatteryTipGroundDetectorTipRingGroundStartSignaling(cont.)IdleState(On-Hook):PBX/FXOmonitorstipforground.BatteryfromCO/FXSappearsonringlead.COorFXSModulePBXorFXOModuleRingGen.-48VDCBatteryTipGroundDetectorTipRingCO/FXSSeizure:CO/FXSgroundstipleadandsuperimposesringingvoltageoverringleadbattery.COorFXSModulePBXorFXOModule-48VDCBatteryTipGroundDetectorTipRingRingGen.GroundStartSignaling(cont.)PBXSeizure:CO/FXSsensesDCcurrentfromthePBXandremovestheringground.PBXSeizure:PBX/FXOtipgroundandringingaresensed,andPBXclosestheloop,thenremovestheringground.Note:ThePBXmustsensetheincomingseizure(tipground)within100ms.Thistimingrequirementhelpstoprevent“glare.〞COorFXSModulePBXorFXOModuleRingGen.-48VDCBatteryTipGroundDetectorTipRingCOorFXSModulePBXorFXOModule-48VDCBatteryTipGroundDetectorTipRingRingGen.GroundStartSignaling(cont.)E&MSignalingPBXtoIntermediateDeviceTypeLeadOn-hookOff-hookIMGroundBattery(-48VDC)IIMOpenBattery(-48VDC)IIIMGroundBattery(-48VDC)IVMOpenGroundVMOpenGroundIntermediateDevicetoPBXTypeLeadOn-hookOff-hookIEOpenGroundIIEOpenGroundIIIEOpenGroundIVEOpenGroundVEOpenGroundSeparatesignalingleadsforeachdirectionE-lead(inbounddirection)M-lead(outbounddirection)AllowsindependentsignalingME&MTypeIPBX-48VDCOff-hook-48VDCChannelBankor

CiscoVoiceEquipmentMEEOpenOn-hookOn-hookOff-hookE-LeadDetectorM-LeadDetectorME&MTypeVPBX-48VDC-48VDCMEEOpenOn-hookOff-hookOff-hookOpenon-hookE-LeadDetectorM-LeadDetectorChannelBankor

CiscoVoiceEquipmentME&MTypeIIPBX-48VDC-48VDCMEEBattery(closed)off-hookSBSBSGSGOpenon-hookGround(closed)off-hookOpenon-hook4-wire,fullylooped,nonsymmetricalE-LeadDetectorM-LeadDetectorChannelBankor

CiscoVoiceEquipmentME&MTypeIIIPBX-48VDC-48VDCMEEBattery(closed)off-hookSBSBSGGround(open)on-hookGround(closed)off-hookOpenon-hook4-wire,partiallyloopedSGE-LeadDetectorM-LeadDetectorChannelBankor

CiscoVoiceEquipmentME&MTypeIVPBX-48VDC-48VDCMEEGround(closed)off-hookSBSBSGOpenon-hook4-wire,symmetrical,leastnoiseGround(closed)off-hookOpenon-hookE-LeadDetectorM-LeadDetectorChannelBankor

CiscoVoiceEquipmentTrunkSupervisionSignaling—

WinkStartDigitsForwardedWinkRequestforServiceRegisterFoundCalledNumberAnswersLocalEndHangsUpRemoteEndTerminatedM-Lead-48V0VE-Lead-48V0VLocalPBXTrunkSupervisionSignaling—

DelayStartDigitsForwardedRequestforServiceRequest

AcknowledgementRegisterFoundCalledNumber

AnswersLocalEnd

HangsUpRemoteEnd

TerminatedM-Lead-48V0VE-Lead-48V0VLocalPBXTrunkSupervisionSignaling—

ImmediateStartWinkM-Lead-48V0VE-Lead-48V0VLocalPBXRequestforServiceLocalEnd

HangsUpRemoteEnd

TerminatedCalledNumber

AnswersDigitsForwardedRegisterFoundCentralOffice2w-4wHybrid2-to4-WireConversionandEchoEchoisduetoareflectionImpedancemismatchatthe2w-4whybridIsthemostcommonreasonforechoReceiveDirectionTransmitDirectionRxandTxsuperimposed2-WireLocalLoopEchoinVoiceNetworksDelay