Telephone System Overview
 

 This slide presentation is a HTML version of a lesson plan originally built in Macromedia for CDA-2502 by L. Scott Freudenthal. It is intended to be presented in a classroom environment with the accompaniment of a lecturer (i.e. Scott) and a ~52 inch monitor (thus the large font selections).  
 


Why are we studying the phone system?
 


 Why are we studying the phone system?

The Phone system is the largest network in the World with over 170 million terminals (phones).
 



 
 Three major components:

  Central Switches

  PBX's

  Phones 


  Implementation media:

  Twisted Pair               Fiber optics

  Microwave                 Satellite links



Access and Control

  Access on demand

  Centralized control



Implementation Topologies:

  Star

  "Snowflake"
 


 
 

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What is a PBX? 

Switching Device, may be analog or digital.

Reduces cables to Central office switch.
 
Internal calls handled internally.

Reduces dependence on phone company.


 
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Digital PBXs

  Faster than Analog.

  Higher data rates.
 
   More Features.
    - Call Back
    - Call Fwd
    - Least cost routing.



 
Digital PBXs

"Codec" - Coder-Decoder.
 
Digitized voice on digital phones.
 
May use analog devices witha digital switch.


Digital PBXs
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Bandwidth for Voice call

Analog call requires 4kHz bandwidth, spaced by 4kHz.

Digital call requires 64kbps.

WHY??



 
Bandwidth for Voice call

Codec digitizes at 8kHZ.

8 bits used to represent each sample.

8,000 samples x 8 bits/sample = 64,000 bps



 
Phone Systems

Integrated Services
Digital Network
 



 
ISDN

Integrated Services

Digital Network

-End to end digital network

 



 

ISDN

        Two types:

        1) PRI - Primary Rate Interface.

        2) BRI - Basic Rate Interface.
 



 
ISDN

Primary Rate Interface.

  Interconnects switches with ISDN link.

   Typically a T1 line.

   23B + D



 
ISDN

Basic Rate Interface.

  Connects ISDN terminals (phones) to the switch.

  Typically a twisted pair.

  2B + D



 
ISDN

        What is 2B + D?



 
ISDN

        What is 2B + D?

         2 - 64,000 bps clear channel

         1 - 16,000 bps control channel 

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ISDN

  Possible Applications
  Simultaneous Voice and Data Calls
  Automatic Call Distribution
  Automatic Call Return
  Call Screening
  Selective Messages
  Selective Forwarding
  Caller Authorization
  Automatic Database access / Voice Response



 
Phone Systems 

 isdn-wo
 



 
Data over phone systems 

Analog phone lines: must convert digital data (computer) into analog data.
 



 
Data over phone systems 
 
Modem:
Modulator/Demodulator.
 



 
Data over phone systems 
 
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Data over phone systems 
 
Speeds from 300 up to 56,000 bps with compression over analog phone line.
 



 
Data over digital phone lines 
 
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Data over digital phone lines 

Using switched digital end to end phone line, up to 64,000 bps.

Modem not required, data access (DSU) can be built into the phone.
 



 
Carrier data services 

Dedicated analog circuits.

Up to 19,200 bps

Higher throughput with compression
 



 
Carrier data services 

Dedicated digital circuits.

DS-0 : 64 kbps, usable 56
DS-1 : (T1) 1.544 Mbps (24 x DS-0)
DS-2 : 6.312 Mbps (3 x DS-1)
DS-3 : 44.736 Mbps (7 x DS-2)
DS-4 : 274.176 Mbps (6 x DS-3)
 



 
Carrier data services 

Variations, other data offerings:

Switched-56
Fractional T1
Frame Relay
SONET
Native LAN Link
 



 
Phone Systems 

 FCCJ's Phone System

Northern Telecom Meridian

One switch per Campus
"Snowflake" topology
ISDN to every desk
 



 
Phone Systems 

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Phone Systems 

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Phone Systems 

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