Hello everyone. I'm new to the DC online scene and just recently hooked up my DreamPi setup and used it for the first time. Anyway, I think that I may have found an alternative to the diy and commercial line voltage inducer. While trying to get my setup working I realized that neither my A or B modem was going to work without some kind of line voltage. I decided to see if I had anything laying around the house that I could use before ordering the parts and building my own. Luckily I found an old expired Magicjack voip usb dongle that seems to work. I subscribed to the Magicjack service four times with four different dongles in the past and can say with confidence that the product provided dialtone, ringer voltage etc just like an actual analog phone line. Here are some specs that I found for the first generation dongle:
50VDC talk battery
4.1VDC off-hook battery
12.5ma loop current
85VAC ring voltage, but I also read 63VAC from one of the Version 1 Magic Jacks
Here's the website where I got the informationhttp://www.sandman.com/magicjackbull.html
The specs start about two thirds down from the top of the page.
Please keep in mind that I don't own any of the later generation Magicjack products and can't confirm whether they work or not. The specs on all of the units look similar so I think that there is a good chance that they will.
For those who are wondering, here is how you go about hooking it up. First, you'll need to plug the Magicjack dongle into an available usb port on your Raspberry Pi using a short usb extension cable. Unfortunately you can't plug it into the Pi directly because it ends up blocking all of the other ports. The Magicjack is powered by the Pi, so make sure that your power supply is up to the task. I used an iPad power adapter and it seems to work fine. Next, the Magicjack phone line needs to be connected in parallel to the phone cable running between your usb modem and the Dreamcast modem. This can be accomplished in one of two ways. One way to do it would be to use a 3 way phone line splitter/coupler. This allows three devices to share the same phone line. Make sure that the splitter or coupler that you use is for a single line, and not for two separate phone lines.
or here's another type
The other method, which is cheap or free, would be to take two phone cables and cut them in half (I used the type of cable that's provided with a dsl modem to connect the wall plate to the modem because the gauge of the wire was larger and the individual conductors were easy to identify) but be sure not to cut off the plugs. I wouldn't recommend using the type of cable that has the clear insulation due to the fact that the individual wires in the cable are extremely thin and not color coded. Once you have the two cables cut in half, take three of the half cables, strip the insulation back about two inches or so to reveal the four individual conductors within each cable. Next, strip enough of the insulation on each of the four conductors on the cut ends of the three cable pieces to allow them to either be twisted together or spliced using whatever method you choose. You want to connect the same colors together so that you have four three way splices with like colors connected together. If you don't have a soldering iron and heat shrink you could just twist the wires together and wrap black vinyl electrical tape or even scotch tape on the bare wires to prevent them from shorting out. That's basically it. Connect one end of your cable to the Dreamcast modem, one to the usb modem and the last one to the Magicjack.
Sorry for this being a little on the long side and not very detailed. I'll do my best to answer any questions and may try to post pictures of my setup.