Why Does the Phone Still Work When the Electricity Goes Out?

One of the relative miracles of modern times is the reliability of the phone system. The power goes out fairly often for most people. Sometimes it is only out for a second, but other times it can be out for minutes, hours or even days. Your telephone, on the other hand, is always working (as long as you pay the bill). Why is that?

The article How Telephones Work talks about the simplicity of phones and the telephone network. The article shows you how, with just a 9-volt battery and a resistor, you can create your own intercom system using two normal telephones. A phone will work as long as it is getting between 6 and 12 volts at about 30 milliamps. In other words, it takes very little power to operate a telephone.

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Between your house and the phone company's office there is a dedicated pair of copper wires for your phone. Those wires are almost always buried, so ice storms and hurricanes will not cut them. The phone company supplies the power that your phone needs using your dedicated copper pair.

So even if the power goes out in your house, the phone still gets the power it needs through the phone line. And at the phone company office there is an extensive battery system, as well as a backup generator, to supply power during a power failure. If the power goes out, the batteries and generators keep the office fully pow­ered. Therefore, all of the phones connected to the office are fully powered as well.

Originally Published: Apr 1, 2000

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Landline Phones During Power Cuts FAQ

Does a landline phone die when the power goes out?
All corded phones continue to work during power failures. Cordless phones don't.
Why do landline phones work during a power outage?
In order to work, phones require six to 12 volts at around 30 milliamps. Because they run on minimal power, the phone company has enough generators and batteries to make sure they continue to operate.
How do landlines get power?
Each landline has a pair of copper wires connected to it. These wires are underground, and so are protected from the elements. Phone companies supply power to these wires in order to keep your phone in working condition.
Do I still need a landline phone?
Because a landline phone continues to work during power failures, keeping one makes sense especially if you live in an area that's susceptible to storms and extreme weather conditions. That way, you will be able to stay connected with the outside world.
Do rotary phones work during power outages?
Rotary phones are corded phones, so they will continue to work during power outages.