ANT is a desktop ISDN telephony application written for GNU/Linux. It supports
OSS (Open Sound System) and I4L (ISDN4Linux). It directly interfaces OSS and
ISDN devices, so there is no need to install extra software or hardware like
PBX (Private Branch Exchange) or telephony cards, if you've got direct access
to an audio capable ISDN card (teles or HiSax chip-set, e.g. AVM Fritz Card)
and a full duplex sound card or two sound devices.