If your computer is equipped with an ISDN card,  you can use it,  provided there is a hardware level driver for that specific type of card.

In order to find out for which ISDN cards a driver is available,  you will have to consult the documentation.

You will find the information about the supported ISDN cards in README documents.

Attention:
Many cards (for example Teles,  AVM,  ELSA) use the HiSax driver,  although none of these cards is called HiSax.

The HiSax driver is a driver for passive ISDN cards,  equipped with a certain type of Siemens chipset.  Read the document README.HiSax for a list of these cards.

ISA Plug & Play cards have to be configured first with isapnp.

There are also some cards that have to be loaded with firmware before use.

After you have added the driver to the kernel,  you will need some programs to make use of your ISDN card.
You will find them in the packages isdn4k-utils and conf-isdn-account.

One of those programs is the script isdn.

It adds the driver of your ISDN card to the kernel and uses your ISDN card to:

1. Make a connection with the Internet
2. Make a call-out connection with other systems (branches,  customers,  etc.)
3. Allow other systems (branches,  customers) to call in on your Linux system.

In the first and second case the connection can be completely transparent.  Which means:

• that an automatic connection is made if you want to approach the Internet or another system.
• that the link will be disconnected automaticaly,  if there is no traffic over the link during an adjustable amount of time.

This script is configured by a number of configuration files which are created with the program /usr/bin/conf-isdn-account.