I've had nearly a week of working with my SPA-3102 and I have to say that basic setup is a breeze. Within an hour of opening the package, I had it connected and was making and receiving VoIP calls. Another hour or so and I had my PSTN line connected and inbound calls were ringing on the phone I had connected to the FXO port. But this little piece of hardware has so many features and capabilities that I just couldn't stop there. It can handle a total of 2 inbound VoIP accounts and six, count 'em, 6, outbound accounts. OK, two of the outbound are associated with your two inbound but, still, that's a total of 6. And that doesn't include the phone line from your phone company.
Things start to get a little tricky when it comes time to configure these various accounts and choosing one or another to dial your outbound call. I have accounts with SIPphone, FreeWorldDialup, Callcentric and a few others. The only account so far that has any outbound calling credit on it, though, is my Callcentric account. So, I need to configure my router appropriately and that means dial plans. What are dial plans? You can look it up in this Wikipedia entry but, for our purposes, let's just say they're strings which tell the router how to interpret the keys you hit on your phone's handset. You could direct the router to
1) Send 311, 611 and 911 calls directly to your PSTN (i.e. dial the number through your telephone company's line),
2) send all calls that start with "9" to the PSTN line (ditto),
3) send all calls that start with "#1" to your primary SIP provider, making a VoIP call to either another VoIP user or a PSTN line,
4) send all calls that start with "#2" to your secondary SIP provider (ditto),
5) send all calls that start with "#3" to your tertiary SIP provider (ditto),
6) send all other calls to your primary SIP provider (ditto).
This is, in fact, a slightly simplified version of what I have set up as my dial plan. And let me say it took a lot of forum-reading, thinking, experimenting and, ultimately, having a conversation with a VERY good friend to rationalize and simplify it. As a matter of fact, if you live with somebody and share your phone with them and they're NOT a techno-nerd, I'd recommend you use something similar.
What else have I done? Calls that come to my PSTN line ring on the handset that's plugged into the SPA3102. That means I can take ALL calls with that one handset. And, as you can see from my dial plan, I can dial PSTN calls from that handset, too. And that means that, ecept for backup in the case of a power outage, I don't need to have a phone plugged into my PSTN line.
OK, time to back off again and let that all sink in. I'll have more later. I still haven't discussed all of this box's capabilities.