VOIP is internet based telephone. Lose power, internet, router, lose phone. AT&T keeps trying to sell me VOIP service and I keep telling them "My POTS line never goes out, even if power's off for days. It just works." They'll argue and I'll simply ask "OK... if I don't have my VOIP phone on a UPS then how long will it work if my house is without power?" That usually shuts them up. The answer is "It won't."It's the phone company. I don't believe they use VoiP. I always thought VoiP needed Internet equipment to route your calls over the Internet not the phone lines.