思科VOIP语音技术培训.ppt

Chapter2:

IntroductiontoAnalogTelephony2-1Copyright?1998,CiscoSystems,Inc.

ObjectivesUponcompletionofthischapter,youwillbeabletoperformthefollowingtasks:Givenananalogtelephonynetwork,identifytheroleofeachcomponentwithinthenetwork.Thecomponentsaretelephones,lines,loops,switches,andtrunks.Givenananalogtelephonynetwork,describethetelephonysignalingonlinesandtrunksGivenatelephonynetwork,tracethepathofatelephonecall

TelephoneCallComponents2-3Copyright?1998,CiscoSystems,Inc.

TelephoneCallComponentsTelephoneLocalloopVoiceswitchCO(centraloffice)PBX(privatebranchexchange)Trunks

TelephoneComponents2-5Copyright?1998,CiscoSystems,Inc.

Handset(receiverandtransmitter)SwitchhookHybrid(2-to-4wireconverter)SidetoneDialerRingerTelephoneComponentsTelephone

CompanySwitchTelephone2-WireLocalLoopRingerSwitchHookLoopLengthComp.Dialing(PulseorTone)BalanceNetwork2-Wire4-WireHybridReceiverTransmitter

TelephoneSignaling2-7Copyright?1998,CiscoSystems,Inc.

TelephoneSignalingSupervisorysignalingReleaseconnection(on-hook)Requestforservice(off-hook)RingingAddressing(dialeddigits)PulseDTMF

On-HookTelephoneSwitchLocalLoopLocalLoop-48DCVoltage(Battery)DCOpenCircuitNoCurrentFlowHandsetoncradle

andswitchhookisopen

LocalLoopLocalLoopOff-HookClosedCircuitDCCurrentDialToneTelephoneSwitchOff-Hook

RingingLocalLoopLocalLoopOff-HookClosedCircuitRing-BackToneDCCurrentRingingVoltageTelephoneSwitch

Ringing(cont.)UnitedStates

Cadence

Europe

Cadence

0.40.40.22Sec2Sec4Sec

PulseMake(CircuitClosed)Break(CircuitOpen)Off-HookDialingInterdigitNextDigitPulsePeriod50ms—20pulsespersecond

100ms—10pulsespersecondUS:60/40Break/Make700ms

DualToneMultifrequencyDTMF123456789*0#120913361477697770852941Timing:60msBreak40msMake

InformationalSignaling—CallProgressIndicators(UnitedStates)ToneFrequency(Hz)OnTime(sec)OffTime(sec)DialBusyRing-back,lineRi