The libpri is a C implementation of the Primary Rate ISDN specification.
It was based on the Bellcore specification SR-NWT-002343 for National
ISDN.  As of May 12, 2001, it has been tested work with NI-2, Nortel DMS-100,
and Lucent 5E C ustom protocols on switches from Nortel and Lucent.

WWW: http://www.asterisk.org/downloads/libpri/