Spencer is the inventor of Asterisk, a free software program that establishes phone calls over the Internet. handles voicemail, caller ID, teleconferencing and other features for the phone.a decent-size company can rip out its traditional phone switch, even some of its newfangled Internet telephone gear, and say good-bye to 80% of its telecom costs
http://www.forbes.com/forbes/2006/0410/063.html