IAXmodem is a software modem written in C that uses an IAX channel (commonly provided by an Asterisk PBX system) instead of a traditional phone line and uses a DSP library instead of DSP hardware chipsets.
Callware VoiceOne is an easy to use web based GUI for the Asterisk PBX. It gives full control over settings through a simple admin panel. You can manage extensions, preferences, POTS/ISDN/VoIP trunks, queues, and rules sets and dynamically create IVRs.