isdn4linux is a set of kernel modules which are part of the Linux
kernel. It consists of the main module
isdn and the
actual hardware driver that control some specific card.
In addition, the package
isdn4k-utils contains utilities to
make use of ISDN specific features.
Please note that since kernel 2.6.0 isdn4linux is considered legacy.
It has been superseded by the new mISDN drivers (see question
mISDN is the successor of isdn4linux, and also consists of kernel modules that are part of the Linux kernel. The mISDN modules have been rewritten from scratch since the old isdn4linux modules were difficult to maintain.
The new mISDN modules are based on the CAPI interface (see question feature_capi for more details on the CAPI interface). Not all ISDN cards supported by isdn4linux have been/will be ported to mISDN. However, it is planned to create a compatibility layer to allow migration of the existing isdn4linux drivers. Also, ipppd would be replaced by the standard pppd once pppd works as well as ipppd currently does. For the moment, isdn4linux can still be used in parallel with mISDN, but this may change in the future.
For more technical and configuration information about the mISDN driver see question config_misdn.
Generally, isdn4linux can control ISDN cards that are connected to the PC's ISA or PCI bus. Also a few PCMCIA cards are supported. However, isdn4linux can not make use of any devices connected via a serial or parallel interface (which are called 'terminal adaptors'), with only a few exceptions: the Creatix/Teles S0 box for the parallel port, and the Gazel 128 USB. For more details on which cards are supported see section hardware.
Basically, isdn4linux can receive and transmit data via ISDN in several ways
(X.75, HDLC, raw ip, synchronous ppp, asynchronous ppp, V.110). Some of its
utilities offer additional features. Two examples are
allows logging of and reaction to ISDN events (including calculating any charges);
vbox, which provides voice answering machine capabilities. For more
details see the section
At least all countries which use Euro-ISDN are supported, however some pecularities apply. To find more about your country, check the section countries.
Besides this FAQ, take a look at the various man pages and Readme's that come with the isdn4linux package. Then there is the isdn4linux website: http://www.isdn4linux.de. There is also a mailing list on isdn4linux which will give you the most up to date information. To find out more about these great information sources, see section docu. And: check out all the great links listed in question config_links! You may find information in your language, or information specific to your linux distribution.
The latest version of the kernel drivers should be found in the Linux kernel. However, sometimes the Linux kernel does not have the latest version or does not yet support your ISDN card. Additionally, you may need to use the isdn4k-util package. In those cases you could try to get the very latest version that is currently in development. See the section distrib.
You can contact the isdn4linux developers through the www.isdn4linux.de website. Have a look at http://www.isdn4linux.de/contacts.shtml.