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Making Analog calls from a Linksys SPA941/942 IP Phone using the Sipura 3000 ATA PDF Print E-mail
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Written by Web Master   
Tuesday, 14 August 2007

Note: How to instructions are at the end of the article. 

The first thing that might pop into your mind is why would you want to do this? As much as I like VOIP it doesn't work all the time. Most business are not ready to give up their reliable PSTN lines and completely switch over to VOIP.


And why should they have to if they can enjoy the best of both worlds. They can add VOIP lines for long distance savings and still keep PSTN lines for local calls and emergency backup.


I have been using my Linksys SPA941 phone for almost a year now and I have nothing but great things to say about this phone. It feels solid, sound quality is excellent, and it's very reliable. The Linksys SPA941/942 phones also work great with Asterisk/Trixbox deployments.


Recently one of our AtlasVoice clients wanted to implement some redundancy for their virtual PBX setup. I went to talk to them about some options and also configure a Linksys WIP300. The WIP300 quality seems to have improved with the most recent firmware in comparison to the last WIP300 I configured.


The original idea the client had was for the SPA3000 to call forward his current PSTN number to his new VOIP number. If for any reason SPA3000 couldn't forward the PSTN calls it would start forwarding them to either a cell phone number or voice mail. This all sounded great to the client but I have also been using the SPA3000 and in order to do what he wanted it would involve more than one PSTN line and more than one SPA3000 without using a VOIP/Internet setup.

Instead I suggested a much simpler solution. Since the client was using AT&T for PSTN I let him know that he can use what is called “Call Forward No Answer” service. This would allow him to forward his current PSTN number to his VOIP number. In case the VOIP service went down the “Call Forward No Answer” service would ring to either to his cell phone or forward the caller to voice mail. He seemed much happier with this solution as it eliminated an additional piece of hardware.

This got me thinking...if the VOIP service did go down it would be nice if the call forwarding on the PSTN could be deactivated and calls could be answered using one of the office IP phones. I knew about IP dialing but never gave it much thought about using it in this scenario. I looked on the internet to find out if someone had done this. At first I didn't find anything because I was mostly searching for the wrong keywords. I ended up posting what I wanted to do in the Linksys Forums and I quickly got a reply with some helpful information.

I ended up doing some additional searching and I ended up finding the information I really needed on the Sipura site. Sipura is the company that made the SPA3000 before it was acquired by Cisco/Linksys. Reading Sipura's FAQ on the SPA3000 what I wanted to do was called a hotline. And there was some simple examples on how to do what I wanted using two SPA3000 ATA's.

I took the information and made a few changes to implement a hotline using my SPA941 and SPA3000. I configured my Ext2 line on the SPA941 to IP dial the SPA3000 analog line. I also configured the SPA3000 to forward all PSTN calls to the SPA941. I have my Ext1 line configured to use my VOIP account and if that ever goes down I can just hit Ext2 line to dial out using the PSTN line, all this from one IP phone.

I never did hear back from the client if he wanted to implement anything more than the “Call Forward No Answer” service. I did however end up with a nice solution that I can suggest to other Virtual PBX customers.