VoIP at home with a Linksys SPA3102, trails, tribulations but it's working now

Posted on Fri 30 November 2007 in Business


So far my experiments with sipgate VoIP have been good. The next step has been to buy an adapter that will convert our home phone into a VoIP phone. There are two reasons for this. Firstly, the sipgate softphone is fine for me when I'm using my laptop but it doesn't have the same convenience of picking up a phone and dialing. Secondly, we make quite a few calls between the family (my house, mums house and the office) and all those calls soon add up. If VoIP works, we should be able to call each other for free (or at least no more than the one off hardware costs).

Just making and receiving VoIP calls isn't the whole objective though, I need our home phone to continue to ring on our home phone number. We're still keeping the line (it's our broadband connection too) and many of our friends know to reach us on this number. So, I wanted to use VoIP when it works for us, and our traditional line if ever it doesn't.

This is where choosing the right adapter comes in. I had to find an adapter that had an FXS port, and FXO port and an ethernet port. What do all these acronyms mean?

  • **update - read Gareth's comment below!**
  • Your normal analog phone plugs into an ~~FXO~~ port (eg the BT Plug on the wall) You could think of the O meaning 'office phone system' if you like, or perhaps 'O'h what a big phone company.
  • The BT Plug on the wall can only be connected to ~~FXS~~ equipment, that is your regular phone. ~~You could think of FX'S' as 'S'imply my desk phone or 'S'ubscriber/customer to the networks plug on the wall~~
  • I didn't mention it earlier, VoIP = Voice over Internet Protocol if you didn't already know
  • and SIP = Session Interaction Protocol, which is one method for VoIP to work, much the same as you can send a letter in a white envelope or a brown envelope and it's still a letter, you can SIP or you can Skype and it's still a VoIP call

I needed an adapter that had both an ~~FXO~~ port (so I could plug our regular phone into it) as well as an ~~FXS~~ port (so the adapter could be plugged into the wall like a normal phone).
Via the Ethernet cable it gets plugged into our home network (and onto broadband internet via our home router). The adapter has to log into the SIP service (sipgate in my case) so that it can receive calls over VoIP. You'll notice that from my earlier post I now appear to be online( 7808060 ) all the time. That's because our home phone is logged into sipgate ready for the next call.

Anyway, onto which adapter I chose.
I found a linksys SPA3102 which had all the required features. It's the latest incarnation of devices from a company once called Sipura who specialise in Voice of IP products. Sipura were bought by Cisco (Cisco are big in business networks, Linksys is their lower end home/small office brand of networking equipment) and are now a part of Linksys. Most importantly I could find users with some experience of the linksys/sipura devices amongst various forums. Although lots were having problems and there seemed to be a fair few needing to do or waiting for firmware updates, many of the replies were giving solutions. I am always more worried when there is a a lack of forum/troubleshooting activity than I am to see it, I don't like being at the leading edge of technology any more than I have to and forum activity shows a product is being well used. It was also within my budget (free wasn't an option, but the 50 price tag was close enough for me to give it a whirl). Being part of the huge Cisco corporation probably isn't a bad thing either, at least I can have an expectation that the device will be around and supported for a while.

I consider myself a pretty network savvy person but this little grey box (photo at the top) had me confused for several hours.

  • Step 1: open the box, gasp in awe at the simple instructions.
  • Step 2: plug the provided wire from SPA3102 into phone, plug original phone wire from SPA3102 into BT wall outlet (well, actually, the broadband filter but let's not get picky).
  • Step 3: wonder why there is no dial tone and nothing happens.
  • Step 4: decide it must need to be enabled from within the web interface. The next problem was entirely of my own making. I departed from the instructions. The device has TWO ethernet ports. one for "internet" one for "computer". Now, if I had a cable modem that presented an ethernet port as it's connection to the world I could probably follow this part, but I, along with many others have ADSL and a wireless router. I plugged the "internet" part into my router and didn't bother moving my PC's ethernet wire from the router to go via the SPA3102. I couldn't connect to the web interface, I couldn't hear any dial tone on the phone (the instruction said I could configure things through a voice menu). I could see the unit had collected it's IP address from my router but I just couldn't connect.
  • Step 5: Decide to read the instructions and do it the strange way. Web configuration now working! Realisation now dawns, it's not strange at all, the device has a firewall and can only be configured from it's LAN side, not the Internet WAN side. It doesn't know that it is already behind a firewall router so the creators took the sensible approach of making it be configured only from it's own Ethernet side. It looks like
  • Step 6: Lesson learnt, now how to configure it so i get a dial tone...
  • Step 7: Realisation dawns that it is already configured to give the regular phone a dial tone. I don't hear a dial tone.... "Houston, I have a problem". Is the unit faulty? Not likely, electronics are pretty good in my experience, it's normally something obvious... like the wire. Unplug everything and look very closely... yes, it's the wire! The wire they provided is an RJ11 plug. It's a small squareish plug with 4 wires, or at least 4 slots where wires can connect. Except telephones only use 2 wires. My old cordless dect phone (a couple of years old BT Freelance XD 500 as it happens) uses the outside two slots of the connector. The SPA3102 uses the inner two slots. Ho hum, off to the web to order 9 worth of wire adapters, most of the cost made up from carriage (BT to RJ11 so the phone can use it's own wire to plug into the SPA3102, and an RJ11 to BT so I could plug the SPA3102's supplied wire into phone line).
  • Step 8: The instructions at this point became very vague. Well, actually, they didn't exist (note to self, never again gasp in awe when technical instructions look simple). I had to log on to the Linksys web site to find answers of how to do things. As the device needs broadband to work, that's not so big a deal but it would have been nice to have a PDF manual or at least where to go for a PDF manual.

On the plus side, the device is cleverer than I thought. It let's me:

  1. Receive a POTS (Plain old Telephone system) call - and ring my regular phone.
  2. Receive a VoIP call - and ring my regular phone
  3. Make a VoIP call - once configured
  4. Make a POTS call - once configured (I made it so we have to dial #9 to get the regular phone line for calling, VoIP is cheaper but POTS has tried and tested reliability)
  5. Receive a POTS call - forward it to another VoIP destination
  6. Receive a VoIP call - forward it to another POTS destination

There are hundreds of settings on this thing, but very little documentation. Without the Linksys web site I would have never been able to guess how to configure the dial string (so we dial #9 then phone number for POTS call).

So, was it worth the 50 (+ wire adapters!)? Yes. I just wish they'd made the instructions more available.

Next stage of my VoIP experiments, finish making our new Avaya IP Office 500 phone system work as a SIP endpoint