thecoalman - 11:33 am on Jan 14, 2013 (gmt 0)
Being in an earthquake zone I know the hard way that when they strike about the only thing left working is the landline as once the electricity goes offline, so does your routers, modems and VOIP phones unless you have a UPS on all that gear, which I have.
The VOIP modems come with a battery backup that is good for a few hours. We live in an area where if the power goes out it's going to be out a for a while. After hurricane Lee 5 days, during hurricane Sandy it never went out but about one mile away it was out for 2 days. We have a generator so the power issue becomes irrelevant.
The other thing to consider is lot of modern phones for landlines require power to operate even if it's a base phone. The one we have will operate without power but you lose all the extra functions. We also have an old phone with ringer that requires no power at all except the current on the phone line which the VOIP modem does supply.