I went through a similar search a few months back and spent a considerable amount of time researching solutions. I also poseted in this group, but didn't find a suitable solution. I wanted a device that passthru incoming calls on either line to the sole equipment/handset line. I also wanted the handset to use the POTS landline by default (so visitors didn't have to "think" to get 911!) and use the VoIP line if a key prefix was entered before the number.
I did quite a bit of looking around. I didn't want a call forwarder, an Asterisk server, or a Mitel switch. I just wanted a little box I could hide in the closet and forget about.
power outage. Not what I wanted. I want the POTS to always be the default, power on or power off. BTW, the company will ship to you. Just write them an email. They got back to me in a couple days. You can also purchase this box online from France, where I believe it's used fairly extensively.
I also checked out this:
're outside the US too, but actually have a US ordering page. This device too came close but didn't exactly meet my needs.
(BTW, Mark Popek has been posting often to tout a device he markets. I'd look into it further before buying it though. It appears to require manual selection to switch between outgoing lines, although I may be wrong. I wanted completely automatic incoming switching, and at-the-handset selection of outgoing line.)
I finally settled on a relatively expensive US device
does precisely what I wanted. Incoming rings on either line ring my phone and make the other line appear busy to other callers. If you lift the handset to make an outgoing call, you get the POTS line. Dialing *# gives you the VoIP line, and you can proceed with dialing as usual. When you are using one of the lines for the outgoing call, the other line is made busy, just like in the incoming case. If power fails, it uses the POTS line. Perfect! But expensive: about $200. Still, I've dropped my POTS line to minimal service, under $10 per month including tax, and I'm saving a bundle by using VoIP for all else, so this device will easily pay for itself.
The setup is incredibly simple, as you might imagine. It's wired like this:
You're absolutely right, but then I'd have to replace all my phones. I have more than one multi-handset system in the house, all single line at present, and the total cost of replacement would have been greater. More importantly, I actually want a single line phone, so that when you pick it up you get the POTS line by default. I have visitors (including a nanny, other parents, babysitter, or housesitter) who I'd rather not have to educate on the phone system. Even choosing between just two lines is a hurdle that I'd rather not have them contemplate while trying to dial 911 if one of the kids gets hurt or some other emergency arises. In my setup, there's no thinking required in a panic situation when one needs help, no extra buttons to press, and no decisions - just turn the phone on and dial 911. Of course, for "normal" phone calls, you need to press *# first, but that's easily programmable into the speed dial slots. But then again, my case is fairly special. You're right to point out that a two line phone system is probably the way to go for most folks. Perhaps the original poster had a desire similar to mine for line forking/selection.
But why switching between two ANALOG lines? If one of these lines is bound to a VoIP then you need an ATA to convert IP telephony into analog phone signals. Then you need TWO devices. The ATA and this switching box.
But MANY GOOD ATA's really include this function with programmable access to an analog line. So you need only ONE device which cost around 100$.
As I mentioned before the Sipura SPA-3000 does exactly what you need! This device is connected to Ethernet for IP-telephony AND to a POTS line for analog calls. On the other side you connect the SINGLE LINE phone. And there is power-failure fallback to the analog line!
Then you can set up a dial plan, when to use which line. So easily 911 (in Europe 112) can use the analog line. And you can even choose between different VoIP Providers!
I think this point is lost on some folks. Devices like the Sipura offer some pretty flexible options on how it handles what happens when the handset line is picked up and numbers are dialed. A PBX system like asterisk is even more flexible. Dial plans can be QUITE sophisticated.