The magic is done within the telephone system at my office (which is about 90 miles from where I live, but could be 900 miles, or 9,000 miles) does not make any difference.
My cable company is not even aware I have this phone, all they would know is data is being sent and received.
The phone is almost identical to the one on the desk at the office. I can do everything they can do. When I make a "local" call, it is actually local to my office. It would be long distance if I was to call my home number.
Up side, I work at home, and anyone in the office can call my extension number anytime day or night (if I did not put it in do not disturb at 5 pm, which I do).
Has nothing to do with my home phone line.
Down side, it is expensive. The IP card at the office is expensive, the phone is expensive.
When my internet connection goes down, the phone goes down.
Last, voice quaility varies. Some time it is excellent, most of the time it it ok, but sometimes (when internet traffic is high) it breaks up to the point you give up and use the land line. But when I think about the poor quaility I just think of all the money we are saving.
This is new technology, it will improve.
Now this is a business phone, but there are products on the market for home use, I don't know anything about them.
For any business's that may be interested, just talk to your phone system provider. This is the hotest thing since touch tone, and all major manufacturer are in the game.