A defibrillator, also called an automatic external defibrillator (AED), is a medical device that delivers an electric shock to the heart during cardiac arrest. It restores normal heart rhythm by analyzing heart activity through electrodes attached to the patient's chest. If a dangerous cardiac arrhythmia is detected, the defibrillator delivers a controlled shock to restore normal rhythm. This increases the chance of survival by restoring blood circulation and oxygen supply to vital organs. Defibrillators are easy to use and they also provide voice instructions for quick first aid in emergency situations.