Ventricular fibrillation is the main reason for cardiac arrest. The probability for survival decreases by 10% every minute, therefore immediate resuscitation is necessary. Cardiopulmonary Resuscitation (CPR) by trained first responders is already established, when a doctor is not available. Today automated external defibrillators (AED) are available to first responders for an effective therapy of ventricular fibrillation. Thanks to the high reliability of today's automated external defibrillators they can be used by trained first responders without any legal reservations. If a defibrillator is available, a trained first responder is obliged to use it in an emergency.