思科VOIP语音技术培训02_CVO

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
1209
697 1
DTMF 1336
2
1477
3
770 4
5
6
852 7
8
9
941 *
0
#
Timing: 60 ms Break 40 ms Make
2-14—CVOICE—Introduction to Analog Telephony
Copyright © 1998, Cisco Systems, Inc.
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:
2-22—CVOICE—Introduction to Analog Telephony
Copyright © 1998, Cisco Systems, Inc.
Trunks
2-23
Copyright © 1998, Cisco Systems, Inc.
Trunks
CO Trunk
PBX
Telephone Company
2-17—CVOICE—Introduction to Analog Telephony
Copyright © 1998, Cisco Systems, Inc.
Voice Switches
2-18
Copyright © 1998, Cisco Systems, Inc.
Voice Switches
2-2—CVOICE—Introduction to Analog Telephony
Copyright © 1998, Cisco Systems, Inc.
Telephone Call Components
2-3
Copyright © 1998, Cisco Systems, Inc.
Telephone Call Components
• 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
Off-Hook
Off-Hook Closed Circuit
DC Current Dial Tone
Local Loop
Telephone Switch
Switch
Local Loop
2-10—CVOICE—Introduction to Analog Telephony
Copyright © 1998, Cisco Systems, Inc.
Frequency (Hz)
On Time (sec) Off Time (sec)
350 + 440
Continuous
480 + 620
0.5
0.5
440 + 480
2
4
440 + 480
1
3
480 + 620
0.2
0.3
480 + 620
0.3
0.2
1400 + 2060 + 2450 +2600 0.1
Copyright © 1998, Cisco Systems, Inc.
Pulse
Make (Circuit Closed)
Off-Hook
Dialing
Interdigit Next Digit
Break (Circuit Open)
700 ms
US: 60/40 Break/Make Pulse Period
• Given an analog telephony network, describe the telephony signaling on lines and trunks
• Given a telephony network, trace the path of a telephone call
converter) • Sidetone • Dialer
Receiver
2-Wire Local Loop
Balance Network
2-Wire 4-Wire Hybrid
Loop Length Comp.
Switch Ringer Hook
Switch
Transmitter
Dialing (Pulse or Tone)
Ringing
Off-Hook Closed Circuit
Telephone Switch
Ring-Back Tone
DC Current
Switch
Ringing Voltage
Local Loop
Local Loop
2-11—CVOICE—Introduction to Analog Telephony
Local Loops
Telephone Company Switch
Local Loop
Switch
Local Loop
• A loop is the physical pair of wires from the subscriber to the telephone company switch
Copyright © 1998, Cisco Systems, Inc.
Ringing (cont.)
United States Cadence
2 Sec
4 Sec
Europe Cadence
0.4
0.2
0.4
2 Sec
2-12—CVOICE—Introduction to Analog Telephony
• Telephone • Local loop • Voice switch
– CO (central office) – PBX (private branch exchange)
• Trunks
2-4—CVOICE—Introduction to Analog Telephony
Copyright © 1998, Cisco Systems, Inc.
• 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)
0.1
200 to 400
Continuous5—CVOICE—Introduction to Analog Telephony
Copyright © 1998, Cisco Systems, Inc.
Local Loops
2-16
Copyright © 1998, Cisco Systems, Inc.
Telephone Company
Intermediate
CO
CO CO
PBX
PBX
2-19—CVOICE—Introduction to Analog Telephony
Copyright © 1998, Cisco Systems, Inc.
Central Office Switch
• All private phones are directly connected to a CO switch
2-20—CVOICE—Introduction to Analog Telephony
Copyright © 1998, Cisco Systems, Inc.
Intermediate Switch
1000
Switch
7000
Switch
2000
Switch
Switch
8000
Switch
3000
Telephone Company
Switch
• Ringer
2-6—CVOICE—Introduction to Analog Telephony
Copyright © 1998, Cisco Systems, Inc.
Telephone Signaling
2-7
Copyright © 1998, Cisco Systems, Inc.
50 ms—20 pulses per second 100 ms—10 pulses per second
2-13—CVOICE—Introduction to Analog Telephony
Copyright © 1998, Cisco Systems, Inc.
Dual Tone Multifrequency
Informational Signaling—Call Progress Indicators (United States)
Tone Dial Busy Ring-back, line Ring-back, PBX Congestion (toll) Reorder (local) Receiver off-hook No such number Confirmation tone
Switch
Local Loop
-48 DC Voltage (Battery) DC Open Circuit No Current Flow
2-9—CVOICE—Introduction to Analog Telephony
Copyright © 1998, Cisco Systems, Inc.
Switch
9000
Switch
• Switch calls between switches • Connects trunks
2-21—CVOICE—Introduction to Analog Telephony
Copyright © 1998, Cisco Systems, Inc.
Private Branch Exchange
• Given an analog telephony network, identify the role of each component within the network. The components are telephones, lines, loops, switches, and trunks.
Intermediate
CO
Interoffice
CO
Trunk
Interoffice Trunk
CO
CO
Trunk
Private Trunk Line
PBX
2-24—CVOICE—Introduction to Analog Telephony
Copyright © 1998, Cisco Systems, Inc.
Telephone Components
2-5
Copyright © 1998, Cisco Systems, Inc.
Telephone Components
• Handset (receiver and transmitter)
Telephone
• Switch hook • Hybrid (2-to-4 wire
2-8—CVOICE—Introduction to Analog Telephony
Copyright © 1998, Cisco Systems, Inc.
On-Hook
Handset on cradle and switch hook is
open
Local Loop
Telephone Switch
– Sits at the remote site – Acts like a switch/phone, thinks it is a switch
Telephone Signaling
• Supervisory signaling
– Release connection (on-hook) – Request for service (off-hook) – Ringing
• Addressing (dialed digits)
– Pulse – DTMF