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To get your AAH VoIP PBX up and running you'll need four things:

  • a dedicated computer
  • a broadband connection
  • VoIP-capable phones
  • a suitable account with a VoIP service provider

The main thing that determines computer and Internet connection requirements is the number of simultaneous calls you'll want to support. This number determines both the computer that will be needed to run AAH and how big an Internet pipe you'll need.

One of the great benefits of AAH is that it doesn't need a very powerful computer for a small number of lines. The Dimensioning an Asterisk system section of contains claims of handling 3 lines with a Pentium 133 MHz and 16 MB of RAM, but it's much safer to go with a more current system.

I was able to successfully run five lines at once on a Pentium Pro 200MHz with 154MB of RAM, with my Internet connection being the limiting factor. A 700MHz Athlon with a gig of RAM comfortably handled eight lines at once, and was only limited by my VoIP provider. Check the Dimensioning article for more examples.

As noted above, the ability to support more simultaneous calls is more likely to be limited by your Internet connection bandwidth than the processing power you can get your hands on. Depending on factors such as the audio codecs, phone types, and calling features supported, each VoIP call can use anywhere from 20 to 90kbps in each direction (upstream and downstream).

If your VoIP traffic data is routed through your normal Internet connection, you could end up with unhappy voice and data users, especially with the relatively puny upstream bandwidth doled out by most broadband ISPs. So for an office of ten or twenty people, it might be wise to have a DSL line (preferably symmetric) dedicated solely to VoIP traffic.

Once you have the AAH CPU lined up and broadband connection in place, the next piece will be the phones themselves.

A software phone is the cheapest option - since many of the leading soft phones are free - but you do have to have your computer on for it to work, and you'll also want to invest in a decent headset, which isn't free. A SIP phone will run you anywhere from $60 for a Grandstream BudgetTone 101 to $300+ for a Cisco 7960G, but there are plenty of other selections available between $100 and $150.

If you already have traditional phones that you want to keep, you'll have to buy an ATA (Analog Telephone Adapter) for each phone. ATAs are also referred to as FXS gateways and convert the traditional phone's analog interface to Ethernet-connected VoIP. (See this part of our VoIP NeedToKnow for more info.) You can buy single-port FXS gateways / ATAs like the Sipura SPA-1001 for about $60.

Yet another alternative are multi-port FXS gateways, which are basically a bunch of ATAs bundled together in a box with a single network connection. I include this alternative for completeness, but don't recommend it, since multi-port FXS gateway vendors don't seem to have gotten the memo yet about declining prices for VoIP hardware. Examples are $530 for a four-port from Mediatrix to $2,300 for a 24-port gateway from Audiocodes. Some gateways also allow a connection to a PSTN line (this is called an FXO connection), which provides backup during power or Internet outages.

The last item on the shopping list is to line up a VoIP service provider. Most of the "name" VoIP providers like Vonage, AT&T CallVantage, etc. are happy to sell you "business" VoIP service that they host and therefore control. But this isn't what you need to run your own VoIP PBX.

Two companies that do know how to deal with VoIP DIYers are Voicepulse and Broadvoice. Voicepulse describes its VoicePulse Connect! as a "commercial-grade origination and termination service that supports both SIP and IAX". Connect! is a pre-paid service and charges $11/month for each U.S. incoming phone number. Broadvoice's BYOD plan lets you choose from any of their rate plans (from $9.95 to $29.95 / month), but use your own device - including an Asterisk PBX.

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