Telephone Networks (PSTN)

Public switched telephone networks (PSTN) is a worldwide telephone system that manages telephone calls.

PSTN use one of the following technique to establish a communication link

  • Fiber optic
  • Telephone lines
  • Satellite communication
  • Microwave transmission links
  • Cellular networks

It is also use in computer communications through internet by using dial-up lines or dedicated lines.

Dial-up lines

  • It uses the PSTN to establish the connection to internet by dialing a number over mobile phone.
  • It requires some time to establish the telephone connection (depending on location)
  • Configure the protocols before to data transfer
  • Slower communication can’t be used for media streaming. Data transfer rate is in Kbps.
  • Connection of dial up lines is explain below

Dedicated lines

  • It is a connection that is always establish between two communication devices
  • These lines may be analog or digital. But the speed of digital is higher than analog.
  • They are used to connect home and business users to network all over the world

Types of dedicated lines

1. ISDN Lines

  • ISDN stands for integrated service digital networks.
  • It uses ISDN modems for Data transmission is over the telephone line.
  • ISDN modem must be present at both ends with in the range of 3.5 miles for communication.
  • It provides faster transfer rate than dial-up telephone lines for small business and home users. It provides transfer rate up to 1.54 Mbps.

2. DSL

  • DSL stand for digital subscriber line. It uses the telephone lines for digital data transmission.
  • Faster transfer rates (upto 10MBps) than ISDN.
  • It allows a user to use phone and internet at a time.
  • In DSL, any computer which is close to service provider office will work batter.
  • It is batter for small business and home users.
  • ADSL (asymmetric) is a type of DSL which provide the faster transfer speed.

The rate of receiving data from internet is called downstream rate and sending data is called upstream rate.

3. Cable

Cabling service also provides internet connection by transmitting data over television network.

Faster transfer rates (up-to 50MBps) than DSL.

  1. T-carrier lines
  2. A synchronous transfer mode.

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