One reader asks: "My company is expecting to make the move to VoIP in the next year or so. I would like to learn some basics before the move is made and hopefully be able to ask the rights questions as the selection is made. Without hocking the family jewels, is there a way that I can build some experience?"
A good place to start is an open-source project called Asterisk . This is a package that can let you work your way through the process of building a VOIP PBX that will talk SCCP and SIP. Depending on your Linux experience, you might want to look into something called Trixbox . This is an install CD that installs a version of Centos (a binary compatible OS with Redhat Enterprise Server), Asterisk and several add-on packages that will enhance your learning environment by integrating CRM and IVR (Interactive Voice Response) to mention just a couple of possibilities of what you can work with.
You should be able to run Asterisk on some pretty basic hardware without breaking the bank I have installed this on an AMD Sempron 2 Ghz processor with 512MB memory. You will need a card to connect the Asterisk to a phone line. The economical way to do this is to get a X100P card (or clone) that will run you anywhere from US$10 to US$30. This is good for testing but you probably wouldn't want to put this in a production environment. For multiple phone line installations, you can look at more expandable cards from companies such as Digium that can support 4 or more phone lines. If you were to take this type of setup live, you can install a card that will take a T1 trunk input so that you can get things working with a single card instead of one or more cards with individual phone connections.
Connecting to a phone provider doesn't just have to happen over a conventional copper connection. As you learn more about how Asterisk and VoIP works, you will find a variety of companies interested in your potential business. Several are very willing to set you up with a temporary or low-cost account so that you can become familiar with the process of interfacing Asterisk to an external dial-tone provider. Having this experience is also handy in that in a disaster recovery situation, all you will need is some type of internet connection and you stand a good chance of having some degree of phone service until your regular service can be restored.
You will need to have some phones to test with. There are softphones that run as an application on a computer with a sound card that can get you started with minimal cash outlays. You can purchase phones that will run on SIP and/or SCCP that will allow you to experiment with phones that could be very similar to what you may end up using when your company goes down the VoIP trail. Having multiple phones to work with will allow you to work with ring groups, transfer between extensions, etc. You can even find some of the more popular Cisco VoIP phones that will give you a variety of phones to learn/work with while you are building experience working with this new technology.