Excerpt of my next piece:
Asterisk started life as a cheap voice mail system written by Mark Spencer in 1999 for his startup company Linux Support Services. The Linux company eventually folded in 2001, but Spencer saw that the future was bright for what was to become the open source PBX project. Spencer teamed up with Jim Dixon of the Zapata Telephony Project, and together they formed Digium, a company that provided products and services around Asterisk. Spencer continues to be the lead maintainer for Asterisk.
System requirements for Asterisk are modest and really depend on the number of simultaneous call that need to be supported. Hobby systems with no more than five concurrent channels can run on a PC with a 400-MHz x86-compatible processor and 256MB RAM. More realistic workloads for small businesses with up to 15 simultaneous connections requires PC with 3-GHz x86-compatible processor and 1GB of RAM. Other factors for the choice of hardware are support for voice encoding, call conferencing, and filtering.
Hmmm, I'm on a roll as a starving writer. Yeah, yeah, looking at my tummy, it doesn't look it, but it's true.