What is ISDN? Integrated Services Digital Network

Rapid advanced in computer and communication technologies have resulted into the increasing merging of these two fields.

The lines have blurred among computing, switching and digital transmission equipment and the same digital technique are being used for data, voice and image transmission.

Integrated Services Digital Network (ISDN) is intended to be worldwide telecommunications networks to replace existing public telecommunications networks.

Now, let’s see, what is ISDN?

ISDN means;

  • ISDN is a communication line that allow digital communication, i.e. Data, voice, video and graphics at very high speed.
  • Support wide range of services over a channel
  • Provides single common interface with which to access digital communication services that are required by various devices while remaining transparent to a user’s.

Services that ISDN supports

The all services that ISDN supports are;

  1. ISDN supports voice calls
  2. Data transmissions and Voice
  3. Video conferencing
  4. Fax transmission
  5. Linking to the internet

ISDN is not restricted to Public Switched Telephone Network (PSTN) alone, it may be transmitted via packet switch network.

Types of ISDN network

There are two types of ISDN which are;

  1. ISDN BA / BRI
  • Basic Access / Basic Rate Interface
  • Consisting B channel and D channel based on 64 kbps used for transmitting and controlling information
  • Formula: 2B + 1D
  • For KOBI’s and Home Users.
  1. ISDN PA / PRI
  • Primary Access / Primary Rate Interface
  • It consist 23B channels and 1D channel (use in US) based on 64 kbps
  • It consist 30B channels and 1D channel (use in Europe) based on 64 kbps
  • Formula: 30B + 1D
  • For Internet Service Providers (ISP) and Big Companies.

BroadBand ISDN

BroadBand ISDN is a BroadBand counterpart to integrate services digital networks which provides digital transmission over ordinal telephone company copper wires on the narrow band.

The main purpose of using BroadBand ISDN is to provide transmission over ordinary telephone company copper wires on the narrow band and having speed of maximum 2MBits/Sec to 1GigaBits/Sec. Also related with Asynchronous Transfer Mode (ATM).

Advantages of ISDN

So the advantage of using Integrated Services Digital Network (ISDN) are;

  1. Digital services (digital services having less errors)
  2. Connection is fast
  3. Higher bandwidth
  4. Voice, data and video can all be sent over a single ISDN line.

Disadvantages of ISDN

  1. ISDN is very costly than other typical telephone system
  2. ISDN requires specialized digital devices just like Telephone Company.


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