Category Archives: asterisk

Using the Linksys SPA-3102 as a VOIP ATA

In other blog entries I’ve been discussing a larger project of setting up a personal Voice over IP (VOIP) Asterisk server using the Linksys SPA-3102 VOIP gateway device.

An ATA (Analog Telephone Adapter) allows one to use old fashioned phones on a voice over IP network, or you can just use IP phones. An ATA like the SPA-3102  does not have to connect to an Asterisk PBX though. In a simple form, it can connect to any SIP VOIP provider for cheap Internet calls.   This is the same idea as other Internet phone plans like Vonage, Comcast, and Verizon, but you pay for only what you use, which can be as low as $0.00 a month.

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Personal VOIP/PBX using Asterisk, part 2

This is part two of my series on how to set up an asterisk server for home use on a Linode VPS — but is applicable to any host that doesn’t have additional hardware telephony devices installed in the server. Please refer to Part 1 for how to set up the dummy timing module.

Also, before continuing, please read my little sidebar post about IP telephony codecs. Most specifically the part on adding iLBC codec to the asterisk config. Then “read more” below for the rest of this post.

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IP Telephony Codecs

My first stumbling block when installing and trying to get Asterisk PBX working were the codecs and mismatching. If both ends of a connection can’t negotiate the same codec, the call won’t complete.

I grabbed the recommended asterisk config for gizmo5 and when attempting to place a call to my gizmo call-in number which should have landed it into my PBX I got the following errors and it disconnected:

[Jan 14 01:40:20] WARNING[23334] channel.c: Unable to find a codec translation path from 0x400 (ilbc) to 0x4 (ulaw)
[Jan 14 01:40:21] WARNING[23334] channel.c: Unable to find a codec translation path from 0x400 (ilbc) to 0x2 (gsm)

When trying to determine what went wrong, I found that ilbc is no longer part of Asterisk config, and ulaw is actually G.711 using the  µ-law algorithm. I also found that one can add iLBC codec to Asterisk by agreeing to a license agreement and running a script.

So hence this blog post, so I can document what I’ve learned and hopefully prevent someone else from having same frustrations.

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