Exactly. If your voip (virtually any provider) goes down it has a "fallover" option which sends the call to any other number you prefer. Of course if the voip providers servers go down you are SOL. We had no power for 10 days during Sandy and never missed a call. We kept our cells charged (and our computer based hot-water heater working) by using one of the 3 battery back-ups we couldn't use to watch TV or used our cars when we went out to find food in the dumpsters behind restaurants (JK on that)!. We would have had no POTS line for 10 days since a pole came down in front of our house and took out all the land lines as well as our internet.