This is the kernel part (userland to follow soon) of the latest (and
very probably last) release (version 0.96) of ISDN4BSD. ISDN4BSD has a
homepage at http://www.freebsd-support.de/i4b/.
It gives the user various ways to use the isdn connection: raw data (via
the i4brbch "raw b-channel" device), ppp (via the isp "isdn PPP" device),
voice/answering machine (the i4btel "telephone" device) and ip over isdn
(the ipr device, "IP over raw ISDN").
Supported are a bunch of common and older cards, more to be added soon
after some cleanup. Currently only the european E-DSS1 variant of the
ISDN D channel protocol is supported.