How high is the voltage delivered by a defibrillator?

Defibrillator is a device used to shock the heart back into sinus rhythm when it has stopped working due to a life threatening rhythm disorder known as ventricular fibrillation. A high voltage direct current of the order of 2500 volts is delivered for the fraction of a second. The total energy delivered will be 200 Joules for a biphasic defibrillator while it is 360 Joules for the older variety monophasic defibrillator. Monophasic defibrillators are being gradually phased out as they are less effective.