What do you do if the power is out and you need to charge your cell phone to make an emergency phone call? Don’t worry. There are plenty of potential power sources all around you. One of them is the phone line. In this instructable, I am going to show you how you can use the phone line to power your small electronic such as your phone or other USB devices in an emergency.
Note: This project is intended for emergency situations only. Please be aware of applicable local laws regarding phone lines in your area.
Source : http://www.instructables.com