Automated External Defibrillator (AED) is the electronic device which take cardiograph, in the case of the wounded's heart loses its pump function, give his or her heart strong electronic shocks for the time being and makes it normal.

It do not only analyzing wavy form of heartbeat but also indicating. In addition, because of it indicating with voices and lights or what we have to do is only sticking pads and pushing the shock button, we can use it easily and safety.

Moreover, after giving electronic shocks, AED also gives the indication of Cardiopulmorary resuscitation with voice and if you keep the pads on the wounded, it begins to analze electrocardiogram at every two minutes.

Probability that the life can be helped after the heart stopping beating is proportion to the time which pass between stopping beating and begining of artificial respiration.
The graph which shows this is Drinke's curve graph of lifesaving.

As above-mentioned, when four minutes pass after the heart stop beating, probability that the life can be helped becomes under 50%. But it is called that it takes about 6 minutes a emergency rescue team to reach where the wounded is.

In other word, it is necessary to give first aid earier than the emergency rescue team comes.
So, cardiopulmonary resucitation by the people who happens to be present at where the wounded is (by Stander) becomes important.