Building Blocks of Telecommunications Networks

1
Building Blocks of Telecommunications Networks

• End-users
• Connections
• Nodes

to/from other nodes or end-users
Telephone Network
CO
CO
Trunk
End-user
End-user
Node
Node
End-user Any device which acts as an
input/output device. Connection An association
of channels, switches and other functional units
used to transfer voice signals or
information. Node A point or junction of a
transmission system where end-user Connect.
to/from other nodes or end-users
Data Network
Router
Router
WAN Link
End-user
Node
Node
End-user
2
Ballad of a Telephone Connection

• Use a Telephone set/Modem
• Setup the call establish and activate the
  circuit
• Complete the conversation/ Transfer Information
• Disconnect/Take down the call.

What is a Telephone Set? It is a device which
converts human speech in the form of sound waves
produced by the vocal cord to electrical
signals. These signals are then transmitted over
telephone wires and then converted back to sound
waves for human ears.
Receiver
Audio Sound Wave
To Central Office
Voice Sound Wave
Transmitter
Loop Current Flows When Switch Hook Closed
Call Setup
Switch
CO (Battery) -48V
Telephone
Tip Ring
Closed When Switch Receiver off hook
3
Dial Tone
A combination of 350 Hz and 440 Hz sine waves
sent to the Telephone from the CO indicating
that the network is ready to receive calling
instructions.
Dialing Modes Pulse and Touch Tone or
Dual-Tone-MultiFrequency
Each button sends a dual frequency sine wave
indicated by the corresponding row and column.
Telephone Numbers are decided by CCITT (ITU)
internationally and NANP in North America NP
numbering plan
4
Call Routing
Other Area Codes
CO
CO
972-883
214-516
Trunk
214-516-3999
972-883-2344
Other Exchanges
A call is normally routed through different
carriers boundary
IXC to LEC Connectivity
5
Carriers Boundaries
RBOC
D
POP
LATA3
IXC
POP
POP
B
LATA1
LATA2
CO
CO
C
RBOC
RBOC
A
Call from A to B Local or Intra-LATA Call Call
from A to C Inter-LATA Call Call from A to D
Long Distance Call
IXC Inter-exchange Carrier LATA Local Access
and Transport Area RBOC Regional Bell Operating
Companies POP Point of Presence