Advantages of ISDN

• ISDN offers variable, responsive transmission speeds.
  

Two or more channels can be combined into a single larger transmission "pipe."
Channels can be assembled as needed for a specific application (a large video conference, for example), and then broken down and reassembled into different groups for different applications (normal voice or data transmissions).
Combining B-channels in this manner is called inverse multiplexing, or "bonding".
ISDN is a network architecture that compines all of the advantages of the digital network and digital common-channel signaling and makes them available to the telecommunications user.

• It handles all types of information.

Unlike some other digital communications technologies, ISDN handles all types of information - voice, data, studio-quality sound, still and moving images. They are all digitized, and transmitted at high speeds in the same flow of data.

• ISDN handles many devices and many telephone numbers, on the same line.
  

Up to eight separate telephones, fax machines or computers can be linked to a single ISDN connection, and have up to 64 "call appearances" of the same or different telephone numbers.

As many as eight separate devices (telephones, computers, fax machines, and more) can be connected to the same ISDN line and each given as many separate telephone numbers as needed.

This means that it is no longer necessary to have multiple telephone lines to handle multiple telephone devices, or multiple telephone numbers, or multiple telephone calls. One ISDN line does it all.

• It can support up to three calls at the same time.
  

Two voice, fax or PC "conversations," and one data "conversation" can take place at the same time, through the same ISDN connection.

Perhaps the most important single feature of ISDN, is that it offers inexpensive dialed digital access to the worldwide telecommunications network.

It is no longer necessary to lease costly dedicated lines for high-speed digital transmission, or to limit data speed and accuracy by using modems to convert digital signals to analog pulses.

• Digital-to-analog conversions will go away.
  

Modems to convert the digital signals of PCs, computers, LANs, and other devices to the analog signals needed for an analog network will be replaced.

Instead, high-speed pulses will flow directly from one digital device to another through a totally digital network.

• Many digital connections will become dialed, not dedicated.
  

It will no longer be necessary to lease expensive dedicated digital lines simply to link a high-speed data device to the network.

The deciding factor will be the economics of how fast the line must be and how frequently it is used.

for more details...

reference url s are...

1. http://www.teach-ict.com/
2. http://www.alumni.caltech.edu/~dank/isdn/
3. http://www.alumni.caltech.edu/~dank/isdn/isdn_ai.html#RFCS
4. http://www.data.com
5. http://www.pacbell.com/products/business/fastrak/networking/isdn/info/isdn-guide
6. http://www.adtran.com/support/isu/mpfaq.html