Connect the defibrillator to a defibrillator analyzer with synchronization test feature. Set the defibrillator to deliver low output energy (50 J or less). Confirm that, with the ECG simulator off, the defibrillator does not discharge. Then apply an ECG amplitude sufficient to activate the marker or indicator. Depress the discharge buttons. The defibrillator should discharge in 60 msec or less following the R-wave peak. Most defibrillators will trigger on the first QRS pulse after the buttons are depressed, although some units are designed to delay until the second or third QRS to avoid unintentional discharges.