Do you have phone jacks in the home? If you do, plugging in the telephone line from the modem to a phone jack will power up the other jacks in the home. If you have NID device from the phone company on the side of your home, you may need to disconnect the phone company's lines from your home. Those boxes are put on homes to techs can test to see if the problem is in your home or on their line.
If you home is wired for phone service, if you "backfeed" a jack in the room with the modem, you can plug in phones in other jacks in the home.
I had AT&T uVerse and that is how we did it when we had a land line. The gateway is in my office and feeds the phone jack in there. But the base/answering machine portion of my cordless phone system was in the kitchen. We just plugged in into the jack there and it all worked just fine.http://www.whoopis.com/howtos/telco-basics/