思科VOIP語音技術(shù)培訓(xùn)02CVO課件

1、Chapter 2:Introduction to Analog Telephony2-1Copyright 1998, Cisco Systems, Inc.2-2CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.ObjectivesUpon completion of this chapter, you will be able to perform the following tasks: Given an analog telephony network, identify the role

2、 of each component within the network. The components are telephones, lines, loops, switches, and trunks. Given an analog telephony network, describe the telephony signaling on lines and trunks Given a telephony network, trace the path of a telephone callTelephone Call Components2-3Copyright 1998, C

3、isco Systems, Inc.2-4CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.Telephone Call Components Telephone Local loop Voice switch CO (central office) PBX (private branch exchange) TrunksTelephone Components2-5Copyright 1998, Cisco Systems, Inc.2-6CVOICEIntroduction to Analog

4、TelephonyCopyright 1998, Cisco Systems, Inc. Handset (receiver and transmitter) Switch hook Hybrid (2-to-4 wire converter) Sidetone Dialer RingerTelephone ComponentsTelephone CompanySwitchTelephone2-WireLocal LoopRingerSwitchHookLoopLengthComp.Dialing(Pulse or Tone)BalanceNetwork2-Wire4-WireHybridRe

5、ceiverTransmitterSwitchTelephone Signaling2-7Copyright 1998, Cisco Systems, Inc.2-8CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.Telephone Signaling Supervisory signaling Release connection (on-hook) Request for service (off-hook) Ringing Addressing (dialed digits) Pulse D

6、TMF 2-9CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.On-HookTelephoneSwitchLocalLoopLocalLoop-48 DC Voltage (Battery)DC Open CircuitNo Current FlowSwitchHandset on cradleand switch hook is open2-10CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.Loc

7、alLoopLocalLoopOff-HookClosed CircuitDC CurrentDial ToneSwitchTelephoneSwitchOff-Hook2-11CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.RingingLocalLoopLocalLoopOff-HookClosed CircuitRing-Back ToneDC CurrentRinging VoltageSwitchTelephone Switch2-12CVOICEIntroduction to Anal

8、og TelephonyCopyright 1998, Cisco Systems, Inc.Ringing (cont.)United States CadenceEuropeCadence2 Sec2 Sec4 Sec2-13CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.PulseMake(Circuit Closed)Break(Circuit Open)Off-HookDialingInterdigitNext DigitPulse Period50 ms20 puls

9、es per second 100 ms10 pulses per secondUS: 60/40 Break/Make700 ms2-14CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.Dual Tone MultifrequencyDTMF123456789*0#120913361477697770852941Timing:60 ms Break40 ms Make2-15CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco S

10、ystems, Inc.Informational SignalingCall Progress Indicators (United States)ToneFrequency (Hz)On Time (sec) Off Time (sec)DialBusyRing-back, lineRing-back, PBXCongestion (toll)Reorder (local)Receiver off-hookNo such numberConfirmation tone350 + 440480 + 620440 + 480440 + 480480 + 620480 + 6201400 + 2

11、060 + 2450 +2600200 to 400Continuous0.50.524Continuous, Freq. Mod 1 HzLocal Loops2-16Copyright 1998, Cisco Systems, Inc.2-17CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.Telephone CompanySwitchLocalLoopLocalLoopLocal Loops A loop is the physical pair of

12、 wires from the subscriber to the telephone company switchSwitchVoice Switches2-18Copyright 1998, Cisco Systems, Inc.2-19CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.Voice SwitchesTelephone Company2-20CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, In

13、c.Central Office Switch All private phones are directly connected to a CO switch Two-wire connection to individual analog phones Calls take one of the following paths Switched within the CO Sent to another CO Sent to an intermediate switch (scalability)2-21CVOICEIntroduction to Analog TelephonyCopyr

14、ight 1998, Cisco Systems, Inc.Intermediate Switch Switch calls between switches Connects trunks SwitchSwitchSwitchSwitchSwitchSwitchSwitch1000900080003000700020002-22CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.Private Branch Exchange Used in private sector Remote branch

15、subsystem Switches (eXchanges) calls locally Keeps “l(fā)ocal” calls off public network Fewer trunks to CO Private line between PBXsTrunks2-23Copyright 1998, Cisco Systems, Inc.2-24CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.TrunksTelephone CompanyCO TrunkInteroffice TrunkCO

16、 TrunkPrivateTrunk LineInteroffice Trunk2-25CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.Foreign Exchange Trunks Foreign exchange office Plugs directly into the line side of a switch Acts like a phone/switch, thinks it is a phone Foreign exchange station Sits at the remot

17、e site Acts like a switch/phone, thinks it is a switch2-26CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.DID/DOD TrunksTelephone CompanyDIDYou have a callTelephone CompanyDOD9 527-XXXXTrunk Signaling2-27Copyright 1998, Cisco Systems, Inc.2-28CVOICEIntroduction to Analog Tel

18、ephonyCopyright 1998, Cisco Systems, Inc.Trunk/Line Seizure Signaling Types CO to phone/FXO/FXS Loop start Ground start PBX to PBX E&MType I to VStart signalingWink startImmediate start Delay start 2-29CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.Loop Start SignalingC

19、O or FXS ModuleTelephone, PBX,or FXO Module.RingGen.-48 VDCBatteryCO or FXS ModuleTelephone, PBX,or FXO Module.RingGen.-48 VDCBatteryIdle State (On-Hook):Telephone or PBX has open 2-wire loop.CO or FXS module has battery on ring, ground on tip.PBX Seizure (Off-Hook):Telephone or PBX closes 2-wire lo

20、op.CO or FXS module detects current.CO will return dial tone.TipRingTipRing2-30CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.Loop Start Signaling (cont.)CO Seizure:CO applies AC ring voltage, superimposed over the -48 VDC.When phone goes off-hook, CO removes ring voltage a

21、nd completes circuit.CO or FXS ModuleTelephone, PBX,or FXO ModuleRingGen.-48 VDCBatteryTipRingCO or FXS ModuleTelephone, PBX,or FXO ModuleRingGen.-48 VDCBatteryTipRing2-31CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.Ground Start SignalingIdle State (On-Hook):PBX/FXO monit

22、ors tip for ground.Battery from CO/FXS appears on ring lead.CO or FXS ModulePBX orFXO ModuleRingGen.-48 VDCBatteryTip GroundDetectorTipRing2-32CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.PBX Seizure:PBX/FXO senses tip ground from CO/FXS, closes the 2-wire loop, and remov

23、es ring ground.CO or FXS ModulePBX orFXO ModuleRingGen.-48 VDCBatteryTip GroundDetectorTipRingPBX Seizure:PBX/FXO grounds ring lead.CO/FXS senses ring ground and then grounds tip lead.CO or FXS ModulePBX orFXO ModuleRingGen.-48 VDCBatteryTip GroundDetectorTipRingGround Start Signaling (cont.)2-33CVO

24、ICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.Idle State (On-Hook):PBX/FXO monitors tip for ground.Battery from CO/FXS appears on ring lead.CO or FXS ModulePBX orFXO ModuleRingGen.-48 VDCBatteryTip GroundDetectorTipRingCO/FXS Seizure:CO/FXS grounds tip lead and superimposes r

25、inging voltage over ring lead battery.CO or FXS ModulePBX orFXO Module-48 VDCBatteryTip GroundDetectorTipRingRingGen.Ground Start Signaling (cont.)2-34CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.PBX Seizure:CO/FXS senses DC current from the PBX and removes the ring groun

26、d.PBX Seizure:PBX/FXO tip ground and ringing are sensed, and PBX closes the loop, then removes the ring ground.Note: The PBX must sense the incoming seizure (tip ground) within 100 ms. This timing requirement helps to prevent “glare.”CO or FXS ModulePBX orFXO ModuleRingGen.-48 VDCBatteryTip GroundDe

27、tectorTipRingCO or FXS ModulePBX orFXO Module-48 VDCBatteryTip GroundDetectorTipRingRingGen.Ground Start Signaling (cont.)2-35CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.E&M SignalingPBX to Intermediate DeviceTypeLeadOn-hookOff-hookIMGroundBattery (-48 VDC)IIMOpenBat

28、tery (-48 VDC)IIIMGroundBattery (-48 VDC)IVMOpenGroundVMOpenGroundIntermediate Device to PBX TypeLeadOn-hookOff-hookIEOpenGroundIIEOpenGroundIIIEOpenGroundIVEOpenGroundVEOpenGround Separate signaling leads for each direction E-lead (inbound direction) M-lead (outbound direction) Allows independent s

29、ignaling2-36CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.ME&M Type I-48 VDCOff-hook-48 VDCMEEOpenOn-hookOn-hookOff-hookE-LeadDetectorM-LeadDetector2-37CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.ME&M Type V-48 VDC-48 VDCMEEOpenOn-hookO

30、ff-hookOff-hookOpenon-hookE-LeadDetectorM-LeadDetector2-38CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.ME&M Type II-48 VDC-48 VDCMEEBattery(closed)off-hookSBSBSGSGOpenon-hookGround(closed)off-hookOpenon-hook4-wire, fully looped, nonsymmetricalE-LeadDetectorM-LeadDetec

31、tor2-39CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.ME&M Type III-48 VDC-48 VDCMEEBattery(closed)off-hookSBSBSGGround (open)on-hookGround(closed)off-hookOpenon-hook4-wire, partially loopedSGE-LeadDetectorM-LeadDetector2-40CVOICEIntroduction to Analog TelephonyCopyrigh

32、t 1998, Cisco Systems, Inc.ME&M Type IV-48 VDC-48 VDCMEEGround(closed)off-hookSBSBSGOpen on-hook4-wire, symmetrical, least noiseGround(closed)off-hookOpen on-hookE-LeadDetectorM-LeadDetector2-41CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.Trunk Supervision SignalingWi

33、nk StartDigits ForwardedWinkRequestfor ServiceRegisterFoundCalledNumberAnswersLocal EndHangs UpRemote EndTerminatedM-Lead-48V 0V E-Lead-48V0V Local PBX2-42CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.Trunk Supervision SignalingDelay StartDigits ForwardedRequest for Servic

34、eRequestAcknowledgementRegister FoundCalled Number AnswersLocal EndHangs UpRemote EndTerminatedM-Lead-48V 0V E-Lead-48V0V Local PBX2-43CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.Trunk Supervision SignalingImmediate StartWinkM-Lead-48V 0V E-Lead-48V0V Local PBXRequest fo

35、r ServiceLocal EndHangs UpRemote EndTerminatedCalled Number AnswersDigits ForwardedRegister Found2-44CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.Central Office2w-4wHybrid2- to 4-Wire Conversion and Echo Echo is due to a reflectionImpedance mismatch at the 2w-4w hybridIs

36、the most common reason for echoReceiveDirectionTransmitDirectionRx and Txsuperimposed2-Wire Local Loop2-45CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.Echo in Voice NetworksDelayTalkerListenerTalker EchoListener Echo2-46CVOICEIntroduction to Analog TelephonyCopyright 1998, Cisco Systems, Inc.Echo Is Always Present Echo as a problem is a function of the echo delay, and the magnitude of the echo(dB)Echo Path LossEcho Path Delay (ms)2-47CVOICEIntroduction to Analog