I've just switched from Comcast's VoIP to a third party VoIP provider (the company formerly known as VoIP.com, now a part of Phone Power). When I got my box (slightly smaller than a 3"x5" card and just thick enough to have phone and ethernet jacks on its back), I noticed it had Phone Line 1 and Line 2 as two separate RJ11 jacks. Why they didn't just use a single RJ14 jack is beyond me. It's not like line splitters are that expensive — they retail for a couple bucks and probably cost half that wholesale. But where splitters are apparently plentiful, a combiner, something that takes two separate single-line jacks and makes a single two-line jack out of it, is impossible to find in a store and even extremely rare online. So, how was I supposed to take these two RJ11 outputs and plug them into the single RJ14 jack that serves as input for my house wiring?
I found instructions for rewiring a CAT-5 ethernet cable to do the job, but I didn't want to have to buy a crimping tool to form the plugs, nor did I feel comfortable splicing it into existing phone cords (the last time I tried something like that, it ended badly). But then I had a sudden revelation.
You see, there's really nothing special about telephone cord accessories. A splitter just takes the pins in a given plug and wires them to the appropriate pins in the right jacks. In the splitter pictured above, the first pair on the RJ14 plug is wired to both the first (and only) pair on the L1 jack and the first pair on the L1+L2 jack. The second pair on the RJ14 plug is wired to the first (and only) pair on the L2 jack and the second pair on the L1+L2 jack. All those associated pins are interconnected; there is no special circuitry that separates the connections (i.e., nothing keeping the L1 jack and the first pair on L1+L2 from talking to each other) — that's why these things are so cheap. Further, wires are bi-directional. If you apply an input voltage to one end, it will carry it to the other end; conversely, if you apply an input voltage to the other end, it will carry it back to the first end. Wires don't care which end is labeled "input" and "output".
And neither does a splitter. With all the pins interconnected by wires, you can just as easily send a signal input into L1 and L2, and get the combined output in both the L1+L2 and the RJ14 plug on the back side.
So that's what I did. I connected the VoIP adapter's Phone 1 and Phone 2 jacks to the L1 and L2 jacks of a splitter, and connected the L1+L2 jack to my house wiring input jack. (I could've used the RJ14 plug on the splitter itself instead of another phone wire, but there wasn't enough room around the input jack on the patch panel for a splitter to fit.)
So why is this so important that I bothered writing a blog post about it? Because, as I was searching out a solution to this problem (which apparently plagues users of Vonage equipment as well), I couldn't find this very simple solution. Maybe someone else will stumble upon this blog post as they search for their own solution and discover just how easy it is.