The Asterisk PBX platform has been around for nine years and has drawn interest from a wide range of end users as well as businesses looking to expand on the basic software or add peripherals to make it more attractive to potential users.
Here are a few questions and answers to help get grounded in Asterisk.

What is Asterisk?
Asterisk is an open source PBX written by Mark Spencer that is available for free download. A free beta trial version of a simplified version called AsteriskNow also is available.

The software supports a stand-alone PBX or can function as a gateway between older TDM PBXs and IP networks. It includes features such as voice mail, conferencing, call distribution and voice phone menus, among many, many others.

Asterisk runs on Linux, Solaris, Mac OS and NetBSD, FreeBSD and OpenBSD servers.

The platform supports SIP, MGCP, H.323 and the Inter-Asterisk Exchange protocols.

How popular is Asterisk?
Digium, the company created by Spencer to capitalize on Asterisk, reported more than 1 million downloads in 2007 alone, and the company has been around since 1999. That doesn’t mean all of those downloads are actually used to support phone networks, but it does show considerable interest.

Vendors that incorporate Asterisk into commercial PBX platforms don’t report sales statistics, according to Infonetics Research, which tracks IP PBX sales. Anecdotally, in a 2007 survey of businesses about IP PBXs, just two out of 240 respondents said they used an Asterisk platform.

How many phones can Asterisk support?
The largest deployment Digium knows about is at the University of Pennsylvania, which has more than 10,000 phones.

Why would I want to use an unsupported PBX platform?
The main reason is price -- zero for the software. If you have the time and technical savvy, you stand to save a lot of money initially deploying the system. Over time you can save even more if you have the wherewithal to maintain the system, update it and modify it to your needs. Even with the hardware thrown in, the cost savings can be significant, as much as 90% off the price of a commercially available PBX.

That being said, there are potential downsides, the main one being support. For businesses the size that Asterisk can serve -- up to several hundred -- telecom staff may be lacking. It may be necessary to use professional help no matter what phone system they choose.