What is ISDN in the Computer Network?

ISDN stands for Integrated Services Digital Network. It is used to bridge the Central Office's local loop and the premise connection (home). ISDN uses the existing wiring so that no new cabling is required. It is a digital service that restores the analog plain old telephone set.

An Integrated Digital Network (ISDN) is a network in which digital switching connections are used to transmit digital signals. Integrated Services refers to ISDNs ability to deliver two simultaneous connections, in any merging of data, voice, video and fax, over an individual line. Multiple devices can be connected to the line and sent as needed.

An ISDN is a network, in general evolving from telephony ISDN, which provides end-toend digital connectivity to provide a broad range of services such as voice and non-voice services, to which customers have to create by a limited set of standard multipurpose user network interfaces.


  • ISDN is a mature technology, and it has been around since the late 1980s. It has been tried, tested and works.
  • A worldwide set of standards governs it.
  • It offers symmetrical transfer rates− the transmit rate is the same as the receiving rate.
  • It has consistent transfer rates. If you have a 64 Kbps bearer channel, then it is the speed that you transfer at.
  • It is a competitive price compared to other technologies.


  • An external power supply is required. The telecommunication doesn't supply power for ISDN lines. If the power fails, the mobile phones won't work.
  • Unique digital phones are necessary or a terminal adapter to talk to the existing plain old telephone set devices.
  • It is costly to upgrade a central office switch ($500,000+) to ISDN.
  • If the ISDN fails-the phone fails.

Updated on: 04-May-2021

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