The Care and Feeding of ISDN4BSD
12.6 DTMF Decoding	12 Setting up the	13 Setting up i4b

12.7 300 Baud Soft-Modem

Poul-Henning Kamp contributed code to convert the i4b telephone facility into a 300 Baud V.21 Software modem. It is available in the V.21 subdirectory of the i4b distribution. Please note, that the kernel patch has already applied, so the README is not quite correct here.