An automated external defibrillator is a special type of defibrillator which can be used by people without medical education. A defibrillator is used to treat certain kinds of heart problems using controlled electric shocks. Almost all heart problems are medical emergencies. For each minute, that such a heart problem is left untreated, the chance of survival drops by about ten percent. Even if they are alerted immediately, emergency teams take some time to arrive. For this reason automated external defibrillator have been placed in locations where they are easily accessible, such as airports, and railway stations.