A heart defibrillator is used to send an electric shock to the heart in an effort to restore its natural rhythm. Various types of defibrillators are made that achieve this goal in different ways. The normal defibrillator seen on television or in hospitals is a manual external defibrillator.
An automatic external defibrillator is designed to monitor heart rate through electrodes attached to the patient's chest and delivers a shock when an erratic heart rate is registered. Pacemakers employ defibrillator technology as well. The pacemaker resides inside the chest wall of the patient and is wired to the heart. When an irregular heartbeat is registered, the pacemaker delivers an appropriate shock to re-establish regularity.