This is an update – I just realized that I had an old article in danish lying around, so this is both a translation and additional information.
Through an auction site I bought a german AVM Fritzbox for around 100 USD some time ago. What I wanted, was a direct ADSL connection, without the 10W overhead of my telephone companys ADSL adapter, plus something for playing around with VOIP.
First I learnt some hard lessons about telephone standards. ADSL runs over two different standards: POTS (Plain Old Telephony Services / analog) and ISDN (Integrated Services Digital Network). These are also known – which was new to me – as Annex A and Annex B connections, respectively. Most phone connections in this country are POTS, whereas in germany most connections are ISDN. So the box I had, being german, was Annex B which was probably why the guy who sold it never got it to work. Well, luckily my ADSL was Annex B, but first I had to make my own cable getting from the Fritz’s RJ45 to the RJ11 in my telephone connection – that wasn’t too hard though, just wiring the middle 4 wires straight through.
In my house at that time we actually also had an Annex A connection, and I did find some instructions on how to change the box from Annex B to Annex A in software (it seems to be Linux based), but I didn’t want to risk breaking it. Now I don’t want to give up my ISDN as I would have to get a new Fritz.
What does my Fritz do, then? To start with it does my WLAN and networking (my model unfortunately has only one Ethernet interface, and no USB printing). Then it has two ATA (Analogue Telephone Adaptor) ports, so I have two ordinary telephones attached. Through the ISDN interface these work as ordinary ISDN phones.
Now the magic begins. In addition to being able to use the telehones for ISDN telephony I can set up an arbitrary number of VOIP providers (and numbers). This means that by dialing a prefix, you can actually use any combination of ISDN and VOIP providers. After a run in period, having ISDN as the default, I simply switched over to making all outgoing calls via VOIP, while still being able to receive incoming calls on both ISDN and VOIP. Through a prefix I can manually select any provider other than the default for a specific call.
Furthermore you can reroute calls, so that you can for example have calls to one of your ISDN numbers reroute via a VOIP line to your mobile phone.
Incoming calls can thus come from a number of VOIP suppliers, for instance FWD who have access numbers that let you call via VOIP at local tariffs from a number of countries. I also have a free US phone number that goes straight to my Fritz via IPkall.
Add to this, that you can design your own vanity numbers (just dial **8LOVE for the woman in your life), shortcut numbers (**701), prefixed selections (like always using a particular provider for any call starting with 0054).
It’s really incredible with all the possibilities offered through VOIP, but it does take quite a bit of work to find the solution that fits you. It does take a while to tame the beast, but then almost free telephony is really possible. It is no wonder that fixed line access is coming down.