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Totek - Asterisk VoIP (SIP) News & Technology Source

Would You Like A Professional Telephone System For Your Office Or Home For Free? PDF Print E-mail
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Written by Mike Furlong   
Tuesday, 10 July 2007
Skeptic or not, I can anticipate some of the questions that you're thinking.


"What's the catch?"

Well the software really can be downloaded and used for free. It's called Asterisk. It's available under the GNU Public License. It has developed its own following and even has an annual convention. Commercial systems have also been developed around Asterisk.

Asterisk was originally developed by Mark Spencer, who works at a company called Digium. But many others have now contributed to Asterisk. That's the beauty of open-source software. Running Asterisk gives you the capabilities of a private branch exchange (PBX). Some of the features include voicemailboxes, call forwarding, call screening, call blocking, automatic call distribution (ACD), music-on-hold, complete incoming and outgoing call-logging and reporting, wake-up calls, and interactive voice response (IVR). You know IVR right? The dreaded press 1 if you're impatient ... over and over. It allows you to attach telephones that can call each other extension to extension. Each extension is private and the calls you make from one to another are private. You can hold, transfer, and make conference calls with ease.

"What does Asterisk run on?"

It runs on a PC. The operating system it runs under can be Linux (its first and probably preferred system), or some other flavor of Unix, or even Windows now I believe. But before you ask. Linux is also available free under the GNU Public License. And many people run Asterisk and Linux on an old cast off PC that they bought for $50 on eBay (at least for small systems). Although like any program, the bigger and snappier your PC is, the better it runs. And the more users your system can support.

"How do I make calls from one extension to another?"

You can run a software program on a PC that communicates with the server and functions like an extension on a PBX. The communications between your PC and Asterisk use industry standard Voice Over Internet Protocols (VoIP). Actually there are different protocols available. You can configure which one Asterisk will use for most of the available devices it can communicate with. Session Initial Protocol (SIP) is a widely-used and popular one. You need a PC with a sound card. And you need either microphone and speakers. Or instead of speakers you can use a headset. Most of these programs put a picture of a phone on the screen and you click on the buttons to dial. If there is another PC on your network running a similar program, you call it just like you would on a real PBX. The program digitizes your voice and sends it over your computer network using VoIP.

"Only extension to extension?"

No, of course not. But remember the "catch" that you asked about? Well I never answered that. There may be a number of "catches" with Asterisk and this is the first.

To make calls outside your private phone system you need some sort of connection to the public switched telephone network (PSTN). PSTN that's the existing phone network as you know it, or remember it. Sometimes people also call this plain ol' telephone service or POTS. There are two primary ways to do this. I'll cover the first now and the second later.

Have you seen all the ads on TV lately for VoIP companies? With a VoIP phone you can connect to one of these companies and make and receive phone calls. The VoIP phone digitizes your voice and sends it over the Internet to the VoIP company. The VoIP company has PSTN connections to allow you to make your call to real telephone numbers. And the reverse is also true. The VoIP company has real telephone numbers they assign to receive calls that will automatically go through their system and be routed over the Internet to your VoIP phone. Well Asterisk can be a VoIP phone to those companies. Many of the companies already know about Asterisk and will tell you how to set up your Asterisk system to work with them so any PC in your house can call a real telephone. The "catch" is that these services cost money. And you will need an Internet connection (high-speed). However, you may save money over what your local telephone company charges.