Sticky electrode pads are applied to the person's bare chest, which send information about the heart's rhythm to the machine's computer.Analyze Rhythm: The machine automatically checks the heart to see if a shockable rhythm (like ventricular fibrillation) is present.Deliver Shock: If a shock is needed, the device guides the user (either by voice prompts or by firing automatically) to deliver a high-energy electrical pulse that depolarizes the heart muscle.