Bogen Emergency Call Switch

what do you do if the power's out but you need to charge your cell phone to make an emergency phone call don't worry there's plenty of power sources all around you one of them is the phone line you may have noticed that corded phones don't need to be plugged into an electrical outlet that's because they're able to get the power that they need directly from the phone line itself when the phone is not in use there's a constant DC signal of about 50 to 60 volts in the phone line and when it is in use this drops to between 6 and 12 volts and when the phone rings it changes to a 20 Hertz AC signal of about 90 volts the phone lines generally even have power during a blackout this is because the phone companies maintain their own backup power system before you try and tap into the electricity in the phone line you should check it with a multimeter to see what you're working with at my house I