With a few simple steps you can use the same wires and same phones that your POTS (Plain Old Telephone Service) use. You can have several phones plugged in and they will all ring when someone calls.
This will not allow you to use 2 phones at the same time, on the same call or even two separate calls. it just allows you to use your "normal" phones on your VOIP service through your existing wiring. And it allows you to use your VOIP service more like normal phones.
Do this at your own risk, you can get shocked or injured by doing this incorrectly. This system works for me and my configuration but it may not work for you. Make sure you understand enough about it and decided if it will work for your situation.
Step 1: Materials
You need a VoIP service that have supported phone adapters Skype and Vonage are some of the most well known.
A VoIP Phone Adapter. http://shop.ebay.com/i.html?_nkw=USB+VOIP+phone+adapter&_sacat=0&_trksid=p3286.m270.l1313&_odkw=USB+VOIP+adapter&_osacat=0
(2) Leviton Voice Grade 4-Conductor QuickPort connectors. You can use 6 or 8 conductor ports as well.
(1) Leviton QuickPort Single-Gang Wall plates (a 2 location cover plate)
If you have an older home you might need to buy a single gang electrical box.
Flat screw driver and
Wire insert tool for the quick connect adapters.
A volt meter will come in handy for testing "live" lines but isn't necessary but recommended.
Step 2: Disconnecting Your Land Line
Your POTS line is powered by your local telephone company, even when you don't have service through them. The voltage is about 9 volts when not ringing 40 volts while talking and nearly 120 volt or higher when ringing. If you don't disconnect your incoming line you will ruin your USB Phone adapter and possible your computer.
Start by unplugging every phone or answering machine in your house.
Find where your phone line enters your home (walk around outside if you need to) there will typically be 4 wires (two phone lines). There should be a point at which all of the wires connect. If this is outside your home you may want to relocate this terminal and move it to a more convenient spot. Be smart about this. As long as you don't cut the wires off at a stupid location or cut them too short this is fully reversible. Make sure you have room to work and make some more connections. When you're ready to cut, only cut one wire at a time these wire are still live, it's a good Idea to tape or wire nut the ends so they don't short out or electrocute someone.
Most new homes usually have all of your phone wires routed to one box where all of the wires from each phone jack all connect together. Unless they are labeled you need to test each line to find out which line is the incoming line, or another way to do this is to leave one phone connected, listen for a tone, and then disconnect one set of wires at a time. When the phone stops the line you disconnected last is your outside line. Or you can use a volt meter to test each separately. Identify which set of wires is incoming and leave the rest connected.
If you use DSL for internet you will need to keep the incoming line connected or you will no longer be able to connect to the internet. The incoming line will still need to be isolated and connected directly to your DSL Modem and nothing else. This is why we have to ports to connect. One is for DSL and the other is to connect the phone lines.
Step 3: The Wiring
In short connect one quick port to your incoming line and connect the port to the rest of the phone lines in your house.
Wire your land line to one of the quick port jacks. You do this by inserting one wire into each slot of the connector and using the press down tool or a small screw driver to press the wire down into the slot so that it makes good contact. If the person who wired your home used Cat 5 cable and followed normal wiring conventions each wire should be inserted into the corresponding colored slot. If they used 4 conductor wire, you'll need to figure out which line is line one. Usually it is the Red and Green wires. For line 2 it is the yellow and black wires. Insert the wires for line one into the blue slots and the orange slots for line 2
Its good practice to wire both lines, even if you only have one phone line.
Each phone location will have its own wire running to it, and they should all connect back to one location. If they are not connected already, connect each color of wire from each location together. Blue to blue, green to green, etc. A short piece of wire will need to be added to each color set, because only a single wire can be inserted into the quick port jacks. Wire together and insert each color of wire into its corresponding with all of the wires connected you can put the plate back on the b position. And make sure you tape or wire nut any of the bare ends.
You should have 2 quick ports connected. One to your outside line, and the other connecting to all of the phones jack in your home.
Step 4: Conclusion
This setup will also work for people who want to use a regular POTS phone and VoIP at the same time. (Your VoIP ADAPTER must support this)