思科VOIP语音技术培训02_CVO.ppt

1、Chapter 2:Introduction to Analog Telephony,2-1,Copyright 1998, Cisco Systems, Inc,Objectives,Upon completion of this chapter, you will be able to perform the following tasks,Given an analog telephony network, identify the role of each component within the network. The components are telephones, line

2、s, 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 call,Telephone Call Components,2-3,Copyright 1998, Cisco Systems, Inc,Telephone Call Components,Telephone Local loop Voice

3、switch CO (central office) PBX (private branch exchange) Trunks,Telephone Components,2-5,Copyright 1998, Cisco Systems, Inc,Handset (receiver and transmitter) Switch hook Hybrid (2-to-4 wire converter) Sidetone Dialer Ringer,Telephone Components,Telephone Company Switch,Telephone,2-Wire Local Loop,R

4、inger,Switch Hook,Loop Length Comp,Dialing (Pulse or Tone,Balance Network,2-Wire 4-Wire Hybrid,Receiver,Transmitter,Telephone Signaling,2-7,Copyright 1998, Cisco Systems, Inc,Telephone Signaling,Supervisory signaling Release connection (on-hook) Request for service (off-hook) Ringing Addressing (dia

5、led digits) Pulse DTMF,On-Hook,Telephone Switch,Local Loop,Local Loop,48 DC Voltage (Battery) DC Open Circuit No Current Flow,Handset on cradleand switch hook is open,Local Loop,Local Loop,Off-Hook Closed Circuit,DC Current Dial Tone,Telephone Switch,Off-Hook,Ringing,Local Loop,Local Loop,Off-Hook C

6、losed Circuit,Ring-Back Tone DC Current,Ringing Voltage,Telephone Switch,Ringing (cont.,United States Cadence,EuropeCadence,Pulse,Dual Tone Multifrequency,DTMF,Timing: 60 ms Break 40 ms Make,Informational SignalingCall Progress Indicators (United States,Tone,Frequency (Hz,On Time (sec,Off Time (sec,

7、Dial Busy Ring-back, line Ring-back, PBX Congestion (toll) Reorder (local) Receiver off-hook No such numberConfirmation tone,350 + 440 480 + 620 440 + 480 440 + 480 480 + 620 480 + 620 1400 + 2060 + 2450 +2600 200 to 400,Continuous 0.50.5 24 13 0.20.3 0.30.2 0.10.1 Continuous, Freq. Mod 1 Hz,Local L

8、oops,2-16,Copyright 1998, Cisco Systems, Inc,Telephone Company Switch,Local Loop,Local Loop,Local Loops,A loop is the physical pair of wires from the subscriber to the telephone company switch,Voice Switches,2-18,Copyright 1998, Cisco Systems, Inc,Voice Switches,Telephone Company,PBX,CO,Intermediate

9、,PBX,CO,CO,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,Intermediate Switch,Switch calls betwe

10、en switches Connects trunks,1000,9000,8000,3000,7000,2000,Private Branch Exchange,Used in private sector Remote branch subsystem Switches (eXchanges) calls locally Keeps “local” calls off public network Fewer trunks to CO Private line between PBXs,Trunks,2-23,Copyright 1998, Cisco Systems, Inc,Trunk

11、s,Telephone Company,PBX,PBX,CO,CO Trunk,Interoffice Trunk,CO,CO,CO Trunk,PrivateTrunk Line,Interoffice Trunk,Intermediate,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

12、remote site Acts like a switch/phone, thinks it is a switch,DID/DOD Trunks,Telephone Company,PBX,CO,DID,You have a call,Telephone Company,PBX,CO,DOD,9 527-XXXX,Trunk Signaling,2-27,Copyright 1998, Cisco Systems, Inc,Trunk/Line Seizure Signaling Types,CO to phone/FXO/FXS Loop start Ground start PBX t

13、o PBX E&M Type I to V Start signaling Wink start Immediate start Delay start,Loop Start Signaling,CO or FXS Module,Telephone, PBX, or FXO Module,Ring Gen,48 VDC Battery,CO or FXS Module,Telephone, PBX, or FXO Module,Ring Gen,48 VDC Battery,Idle State (On-Hook): Telephone or PBX has open 2-wire loop.

14、 CO or FXS module has battery on ring, ground on tip,PBX Seizure (Off-Hook): Telephone or PBX closes 2-wire loop. CO or FXS module detects current. CO will return dial tone,Tip,Ring,Tip,Ring,Loop Start Signaling (cont.,CO Seizure: CO applies AC ring voltage, superimposed over the -48 VDC. When phone

15、 goes off-hook, CO removes ring voltage and completes circuit,CO or FXS Module,Telephone, PBX, or FXO Module,Ring Gen,48 VDC Battery,Tip,Ring,CO or FXS Module,Telephone, PBX, or FXO Module,Ring Gen,48 VDC Battery,Tip,Ring,Ground Start Signaling,Idle State (On-Hook): PBX/FXO monitors tip for ground.

16、Battery from CO/FXS appears on ring lead,CO or FXS Module,PBX or FXO Module,Ring Gen,48 VDC Battery,Tip Ground Detector,Tip,Ring,PBX Seizure: PBX/FXO senses tip ground from CO/FXS, closes the 2-wire loop, and removes ring ground,CO or FXS Module,PBX or FXO Module,Ring Gen,48 VDC Battery,Tip Ground D

17、etector,Tip,Ring,PBX Seizure: PBX/FXO grounds ring lead. CO/FXS senses ring ground and then grounds tip lead,CO or FXS Module,PBX or FXO Module,Ring Gen,48 VDC Battery,Tip Ground Detector,Tip,Ring,Ground Start Signaling (cont.,Idle State (On-Hook): PBX/FXO monitors tip for ground. Battery from CO/FX

18、S appears on ring lead,CO or FXS Module,PBX or FXO Module,Ring Gen,48 VDC Battery,Tip Ground Detector,Tip,Ring,CO/FXS Seizure: CO/FXS grounds tip lead and superimposes ringing voltage over ring lead battery,CO or FXS Module,PBX or FXO Module,48 VDC Battery,Tip Ground Detector,Tip,Ring,Ring Gen,Groun

19、d Start Signaling (cont.,PBX Seizure: CO/FXS senses DC current from the PBX and removes the ring ground,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

20、 requirement helps to prevent “glare.,CO or FXS Module,PBX or FXO Module,Ring Gen,48 VDC Battery,Tip Ground Detector,Tip,Ring,CO or FXS Module,PBX or FXO Module,48 VDC Battery,Tip Ground Detector,Tip,Ring,Ring Gen,Ground Start Signaling (cont.,E&M Signaling,PBX to Intermediate Device,Type,Lead,On-ho

21、ok,Off-hook,I,M,Ground,Battery (-48 VDC,II,M,Open,Battery (-48 VDC,III,M,Ground,Battery (-48 VDC,IV,M,Open,Ground,V,M,Open,Ground,Intermediate Device to PBX,Type,Lead,On-hook,Off-hook,I,E,Open,Ground,II,E,Open,Ground,III,E,Open,Ground,IV,E,Open,Ground,V,E,Open,Ground,Separate signaling leads for eac

22、h direction E-lead (inbound direction) M-lead (outbound direction) Allows independent signaling,M,E&M Type I,PBX,48 VDC Off-hook,48 VDC,Channel Bank or Cisco Voice Equipment,M,E,E,Open On-hook,On-hook,Off-hook,M,E&M Type V,PBX,48 VDC,48 VDC,M,E,E,Open On-hook,Off-hook,Off-hook,Open on-hook,Channel B

23、ank or Cisco Voice Equipment,M,E&M Type II,PBX,48 VDC,48 VDC,M,E,E,Battery (closed) off-hook,SB,SB,SG,SG,Open on-hook,Ground (closed) off-hook,Open on-hook,4-wire, fully looped, nonsymmetrical,Channel Bank or Cisco Voice Equipment,M,E&M Type III,PBX,48 VDC,48 VDC,M,E,E,Battery (closed) off-hook,SB,S

24、B,SG,Ground (open) on-hook,Ground (closed) off-hook,Open on-hook,4-wire, partially looped,SG,Channel Bank or Cisco Voice Equipment,M,E&M Type IV,PBX,48 VDC,48 VDC,M,E,E,Ground (closed) off-hook,SB,SB,SG,Open on-hook,4-wire, symmetrical, least noise,Ground (closed) off-hook,Open on-hook,Channel Bank

25、or Cisco Voice Equipment,Trunk Supervision SignalingWink Start,Digits Forwarded,Wink,Request,for Service,Register,Found,Called,Number,Answers,Local End,Hangs Up,Remote End,Terminated,M-Lead,48V,0V,E-Lead,48V,0V,Local PBX,Trunk Supervision SignalingDelay Start,Digits Forwarded,Request for Service,Req

26、uestAcknowledgement,Register Found,Called Number Answers,Local EndHangs Up,Remote EndTerminated,M-Lead,48V,0V,E-Lead,48V,0V,Local PBX,Trunk Supervision SignalingImmediate Start,Wink,M-Lead,48V,0V,E-Lead,48V,0V,Local PBX,Request for Service,Local EndHangs Up,Remote EndTerminated,Called Number Answers

27、,Digits Forwarded,Register Found,Central Office,2w-4w Hybrid,2- to 4-Wire Conversion and Echo,Echo is due to a reflection,Impedance mismatch at the 2w-4w hybrid Is the most common reason for echo,Receive Direction,Transmit Direction,Rx and Tx superimposed,2-Wire Local Loop,Echo in Voice Networks,Delay,Talker,Listener,Talker Echo,Listener Echo,Echo