The main aim of this article is to analysis about automated external defibrillators. An automated external defibrillator (AED) is a moveable electronic gadget that mechanically diagnoses the life threatening cardiac arrhythmias of ventricular fibrillation and ventricular tachycardia in a patient, and is capable to treat them through defibrillation, the application of electrical therapy which stops the arrhythmia, allowing the heart to reestablish an effective rhythm.