tdc 461: basic telecommunications
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TDC 461: Basic Telecommunications. DePaul University 9 April, 2001 LoriLee M. Sadler. Telephone Network Telephone Numbering Format Signaling on Subscriber Loop Analog vs. Digital Information. Central Office Switch Technologies How is a Voice Call Made? Carrier Services. Agenda. - PowerPoint PPT PresentationTRANSCRIPT
TDC 461: Basic Telecommunications
DePaul University
9 April, 2001
LoriLee M. Sadler
Agenda
• Telephone Network
• Telephone Numbering
Format
• Signaling on Subscriber
Loop
• Analog vs. Digital
Information
• Central Office Switch
Technologies
• How is a Voice Call
Made?
• Carrier Services
Public Switched Telephone Network:
AmeritechCentral Office
AmeritechCentral Office
PBX
Subscriber LinesCentrex Lines
IXCPOP
AmeritechTandem Office
IXCPOP
Inter-Office Trunks
Dir
ect
IXC
Tru
nkPOP = Point of PresencePBX = Private Branch Exchange
The PSTN:
• Topology of Connections
• Network=>– Demarcation point (Demarc)=>also called
station drop.
Network Configuration
• Star configuration from the Central Office (CO) to the demarc
• Star or ring configuration from the Central Office to other COs or higher-level offices
• Wire Center or FrameSwitch
• Physical vs. logical connections• Facilities
The Subscriber (Local) Loop
Outside Plant
• Demarcation Point (Demarc)
• Feeders:
• Lateral distribution:
• Branch feeders:
Subscriber Loop Signaling
• Carrier Sense=>
Battery
CentralOffice
-48 v.
The Subscriber Loop
• The Subscriber Line or Subscriber Loop is made up of 2 copper wires twisted together (wires called “tip” and “ring”)
Battery
CentralOffice
-48 v.
The Subscriber LoopIdle Line
• Central Office provides battery power (48 volts DC) to subscriber loop.
• When telephone is ON-HOOK, it keeps loop open (wires are not connected) and there is no current flow.
Battery
CentralOffice
-48 v.
The Subscriber LoopService Request
• Off-Hook signals request
• Request fulfilled by CO
Battery
CentralOffice
-48 v.
North American Numbering Plan (NANP)
• Determines format for dialed numbers.• Administered by BellCore• Format before 1995:
Prefix + 0/1 + N(0/1)X - NNX - XXXX (N digits are 2-9, X digits are 0-9)
• Format as of January, 1995:Prefix + 0/1 + NXX - NXX - XXXX
(N digits are 2-9, X digits are 0-9)
Address Signaling Rotary Pulse Dial
– After pulling dial for digit ‘N’, telephone opens and closes subscriber loop ‘N’ times as dial returns to its original position.
• Dual Tone Multifrequency (DTMF) or Touch Tone– One frequency assigned to each
row and each column.
– Pressing any key sends a 2-frequency signal tone.
ABC
2DEF
31
Oper
0 #*
TUV
8WXY
9PRS
7
JKL
5MNO
6GHI
4
1447 Hz
852 Hz
770 Hz
697 Hz
1209 Hz 1336 Hz
941 Hz
Business Station Set Features
• Access to multiple lines:– Multiple Directory Numbers– Multiple Access to single Directory Number (MADN)– Call Pickup privileges to other lines– Call status indicator lamps and display– Intercom dialing
• Speakerphone• Voice Mail Access
– Message Waiting lamp
Business Station Set Features
• Calling Features:– Hold– Drop– Conference– Transfer– Speed Dial– Call Forward– Call Waiting
TrunksAmeritech
Central OfficeAmeritech
Central OfficeInter-Office Trunks
Repeaters Repeaters
• • •
Analog TrunksAmeritech
Central OfficeAmeritech
Central OfficeInter-Office Trunks
Repeaters Repeaters
• Trunk types:– 2-wire analog trunk– 4-wire analog trunk
Digital TrunksAmeritech
Central OfficeAmeritech
Central OfficeInter-Office Trunks
Repeaters Repeaters
• 1962 (T-1 carrier)
Digital TrunksAmeritech
Central OfficeAmeritech
Central OfficeInter-Office Trunks
Repeaters Repeaters
• Advantages of Using Digital Trunks:
Voice Digitization1 Voice Channel = 64,000 bits/second
Sample Quantize 100111011
8000 samples/sec 8 bits/sample
Call over Digital TrunkAmeritech
Central OfficeAmeritech
Central OfficeInter-Office Trunks
Regenerators Regenerators
• Codec (Coder/decoder) circuits in COs do analog-digital conversion.
• Analog Central Office Switch:– Analog signal is switched internally.
• Digital Central Office Switch:– Digital signal is switched internally.
Channel BanksAnalogSwitch
AnalogSwitch
T-1 TrunkRepeater Repeater
T-1Channel
Bank
T-1Channel
Bank
......
24 AnalogVoice Channels
• T-1 Channel Bank converts between 24 analog voice channels and a single T-1 trunk.– Digitizes 24 voices (codec function)– Combines 24 DS0 signals into a DS1 signal
(multiplexing function)
Central Office Switch Technologies
AmeritechCentral Office
Wire Center Components
• Central Office Switches
• Main Distribution
Frame (MDF)
• Cable Vault
Main Distribution Frame (MDF)
C.O. Switch
Central Office / Wire Center
Switch Side
Cable Side (Protected)
Switch Matrix
ServiceCircuits
CommonControl
DataStore
Trunk Cards
Cable Vault
OutsidePlant
Line Cards
Wire Center Components
• Central Office Switch Components– Common Control
– Data Store
– Service Circuits
Main Distribution Frame (MDF)
C.O. Switch
Central Office / Wire Center
Switch Side
Cable Side (Protected)
Switch Matrix
ServiceCircuits
CommonControl
DataStore
Trunk Cards
Cable Vault
OutsidePlant
Line Cards
Wire Center Components
• Central Office Switch Components– Switch Matrix
– Line Cards
– Trunk Cards
Main Distribution Frame (MDF)
C.O. Switch
Central Office / Wire Center
Switch Side
Cable Side (Protected)
Switch Matrix
ServiceCircuits
CommonControl
DataStore
Trunk Cards
Cable Vault
OutsidePlant
Line Cards
Wire Center Components
• Distribution Frame– –
• Cable Vault• Outside Plant
– –
Main Distribution Frame (MDF)
C.O. Switch
Central Office / Wire Center
Switch Side
Cable Side (Protected)
Switch Matrix
ServiceCircuits
CommonControl
DataStore
Trunk Cards
Cable Vault
OutsidePlant
Line Cards
How is a Voice Call Made?
A Voice Call
• Originating phone goes off-hook.
Central Office
Switch Matrix
ServiceCircuits
CommonControl
DataStore
MDF
LineCards
TrunkCards
A Voice Call• Customer dials number.
Central Office
Switch Matrix
ServiceCircuits
CommonControl
DataStore
MDF
LineCards
TrunkCards
A Voice Call
Phones go on-hook.
Central Office
Switch Matrix
ServiceCircuits
CommonControl
DataStore
MDF
LineCards
TrunkCards
Inter-Office Calls
Central Office
Switch Matrix
ServiceCircuits
CommonControl
DataStore
MDF
LineCards
TrunkCards
Central Office
Switch Matrix
ServiceCircuits
CommonControl
DataStore
MDF
TrunkCards
LineCards
Inter-Office Trunk
Network Structure
AmeritechCentral Office
AmeritechCentral Office
PBX
Subscriber LinesCentrex Lines
IXCPOP
AmeritechTandem Office
IXCPOP
Inter-Office Trunks
Dir
ect
IXC
Tru
nkPOP = Point of PresencePBX = Private Branch Exchange
Residential Services
• Direct Distance Dialing or DDD service
• Party Line Service
Business Services
• Line vs. Trunk Service
• Private vs. Switched Service
Private Line Services• Private Line Service provides a dedicated
circuit between two locations
Private Line ServicesCentral Office
Switch Matrix
ServiceCircuits
CommonControl
DataStore
MDF
LineCards
TrunkCards
Central Office
Switch Matrix
ServiceCircuits
CommonControl
DataStore
MDF
TrunkCards
LineCards
Inter-Office Trunk
• Private Line / Leased Line / Dedicated Line
Private Line Services• Foreign Exchange (FX) Line
• Off Premises Extension (OPX)
Private Line ServicesCentral Office
Switch Matrix
ServiceCircuits
CommonControl
DataStore
MDF
LineCards
TrunkCards
Central Office
Switch Matrix
ServiceCircuits
CommonControl
DataStore
MDF
TrunkCards
LineCards
Inter-Office Trunk
• Foreign Exchange (FX) Line
Private Line Services
Central Office
Switch Matrix
ServiceCircuits
CommonControl
DataStore
MDF
LineCards
TrunkCards
Central Office
Switch Matrix
ServiceCircuits
CommonControl
DataStore
MDF
TrunkCards
LineCards
Inter-Office Trunk PBX
• Off Premises Extension (OPX)
FX Line Example• LhasaLabs Corporation in Chicago has many
customers in New York
– DDD Chgo-NY costs 15 cents per minute
– FX line Chgo-NY costs $800 per month
– LhasaLabs makes about 25 calls to NY each day, each
call lasting about 10 minutes
– SHOULD LhasaLabs GET AN FX LINE?
Private Line Services• Tie Line
• Dedicated Access Line to IXC POP
Private Line ServicesCentral Office
Switch Matrix
ServiceCircuits
CommonControl
DataStore
MDF
LineCards
TrunkCards
Central Office
Switch Matrix
ServiceCircuits
CommonControl
DataStore
MDF
TrunkCards
LineCards
Inter-Office Trunk PBXPBX
• Tie Line
Private Line Services
• Dedicated access to IXC POP
LEC Sw itch
Switch M atrix
ServiceCircuits
CommonControl
DataStore
M DF
LineCards
TrunkCards
IXC Sw itch
Switch M atrix
ServiceCircuits
CommonControl
DataStore
M DF
TrunkCards
LineCards
IXC T runkPBX
Switched Line Services• Direct Distance Dialing (DDD)
• Wide Area Telecommunications Service (WATS)
• IN-WATS (800, 888 services)
WATS, IN-WATS
• WATS=>Wide-area telecommunications services; Refers to outbound calls only, not inbound.
• old style with banded service rates
• Full-time WATS=>
• Measured WATS=>
WATS Example
• Lhasa Labs is located in Chicago and many customers in New York. Lhasa Labs wants to offer a toll free number to its New York customers. Lhasa Labs anticipates using 200 hours per month.– $37.50 per line per month; additional usage at $.15 a
minute –
– Compare to DDD?– Compared to a T1?
Switched Line Services• 900 Services
–
• International WATS–
• Remote Call Forwarding– –
Switched Line Services• Directory Services
–
• Wide Area Telecommunications Service (WATS)–
• IN-WATS (800, 888 services)–
RCF Example• LhasaLabs Corporation in Chicago has many
customers in New York. LhasaLabs wants to offer a local New York number.– DDD Chgo-NY costs 15 cents per minute
– RCF service costs $50 per month
– FX line Chgo-NY costs $800 per month
– Customers in NY make about 10 calls to LhasaLabs each day, each call lasting about 10 minutes
– SHOULD LhasaLabs GET AN FX LINE?
Residential and/or Business Features
• Call Forwarding• Call Waiting• Three-Way Calling• Call Transfer• Calling Card• Speed Calling• Automatic CallBack• etc. etc.
Network Structure
AmeritechCentral Office
AmeritechCentral Office
PBX
Subscriber LinesCentrex Lines
IXCPOP
AmeritechTandem Office
IXCPOP
Inter-Office Trunks
Dir
ect
IXC
Tru
nkPOP = Point of PresencePBX = Private Branch Exchange
Business Services
• Line vs. Trunk Service – Is access to network directly through telephone
sets or through customer switch (Private Branch Exchange or PBX)?
• Private vs. Switched Service – Does network just provide connection (private)
or dial tone (switched)?
Line vs. Trunk Addressing• Each line has a telephone number
associated with it.– –
• A trunk does not have any telephone number associated with it. –