Remember our article on the advantages of landline phones in a disaster scenario? If so, you probably also remember that landline phones receive power through the phone line, and can often stay operational for weeks—even if the rest of the power grid is down. That's because the phone company supplies the power necessary to operate the phone, and will continue to supply power via generators for as long as possible during a disaster.

DIY emergency power phone line

See the red and green wires? Those supply DC power to keep your landline phone operational.

Knowing this, we wondered if it's possible to use this power for anything else, such as keeping a cell phone (or other small USB electronic device) charged. The answer is yes, but it takes a little preparation, tinkering, and wire splicing to make it work.

Emergency phone line power 1

Disclaimer: Be aware that this DIY emergency power source should ONLY be used in legitimate emergencies, as it is highly illegal (as in a felony) to use phone line power for anything but powering a landline phone. This is also potentially dangerous, since you run the risk of shocking yourself or frying your electronic device if something goes wrong. Don't do anything stupid or illegal with this information, and if you do, we are not responsible.

If you'd like to read through the steps in more detail, check out the article on Instructables here. It has some complex-looking wiring diagrams, but the concept is simple: phone cord spliced to a LM7805 voltage regulator, spliced to a USB cable. You can also add a diode to protect your charger if you think anyone might call the phone line.

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