The Care and Feeding of ISDN4BSD
3.3 The Kernel Components	The Care and Feeding	5 Installation and Kernel

4 Prerequisites

In order to use isdn4bsd, you need at least the following:

• a working ISDN BRI S0 bus. For using passive cards this bus must must be a BRI conforming to the DSS1 standard or so-called Euro-ISDN Protocol; if you intend to use a supported passive card, the S0 bus protocol must be one of the protocols supported by the active cards' microcode.
• one of the cards supported by isdn4bsd
• a free slot in your PC, a free IRQ, a free i/o port address range and/or a free memory address range
• some time to configure and recompile your kernel
• and some time to install and configure the userland programs

The most important thing is to read the various man pages, installation instructions and the FAQ!

Some people report that it takes less than an hour to get isdn4bsd up and running but this time usually depends on the experience you have with kernel configuration and ISDN experience in general. I think its safe to say that it takes one to two hours to read the documentation and man pages, one to two hours to configure and compile a new kernel and one to two hours to setup the isdnd configuration file and then test the connection to a remote site.