Q: I'm thinking of switching to the cable company's phone service, but I'm a bit concerned about service during a power outage. What phone services can I count on when the power goes?
A: This used to be an easy question to answer, when the traditional wired telephone system was the only way of placing calls. With calling now possible via cellular networks, cable, the Internet and even optical fiber to the home, it gets more complicated.
The landline phone system remains the most reliable option during a power outage. The central offices, or switching stations, have backup power, and supply enough power through the lines to power corded phones.
Cordless phones, of course, need to be plugged into a wall outlet, so they don't work during a blackout. If you use a cordless phone, also keep a corded one on hand for emergencies.
By comparison, the adapters that connect phones to cable lines can't draw their power from the lines. Cable companies vary in their approach to dealing with the issue.
Comcast Corp. and Cox Communications provide backup batteries in their voice adapters, which should power them for four to eight hours in case of an outage. That's good enough for the typical outage, but not for a recurrence of the Northeast blackout of 2003.
Time Warner Cable, the cable company with the most voice customers, provides a backup battery, but only if the customer asks for it.
Cablevision Systems Corp. sells a backup battery for $45.
The most recent addition to the telephone market - optical fiber - is in this respect similar to cable, and needs power to work. Verizon Communications Inc., which is building out fiber connections under the FiOS brand, provides a four to eight-hour backup battery.
Keeping an Internet phone service like Vonage going in a power outage requires some preparation. You will need to keep both your broadband Internet connection and voice adapter alive. For this, you will need to buy a separate backup battery, also known as an Uninterruptible Power Supply, or UPS. Modems and voice adapters don't use much power, so a low-end UPS for $35 or so should be sufficient.
As with a landline phone, you need to have a corded phone to plug into the voice adapter that goes with your cable, fiber or Internet voice adapter.
Wireless phones have the advantage of having their own batteries, and low power consumption to boot. But they'll only work if the cellular base stations stay alive. Verizon Wireless said it has battery backup on its base stations that should keep them going for one or two days, and it has portable generators that can be deployed when the batteries run out.
Of course, cellular frequencies can get crowded in an emergency, as happened during the 9/11 terror attacks. To minimize usage of the airwaves and increase chances of getting through, try text messaging.
None of this advice will be much good if the power outage is due to an event that also cuts telecommunications lines, like an earthquake or hurricane. Even cellular calls run on land lines for most of the way. But phone and cable lines have a somewhat better chance of surviving a minor disaster, like a windstorm, than power lines, since they're mounted lower on the utility poles. There's also chance they'll keep working if blown down intact, unlike a power line, which shorts out.