This is a *source* package for ISDN support (it really doesn't work
well to precompile this, as you need to set it up specifically for
your hardware), so untar it somewhere like this:

tar xzvf isdn4k-utils.v3.1pre1.tar.gz

Then configure it:

cd isdn4k-utils
make

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NOTE:  For 2.2.x kernels, use isdn4k-utils.v3.1pre1.tar.gz.
       For 2.4.x kernels, use isdn4k-utils-CVS-2001-06-09.tar.gz