The Shock Advisory System or SAS is the standard analyzation system used by all LIFEPAK AEDs. It takes sample of the patients ECG and analyzes multiple attributes of the ECG sample. When the algorithm determines a shockable rhythm is present, the defibrillator begins charging. While the LIFEPAK 300 is charging after a Shock Advised decision with selected energy above 200 Joules, the defibrillator will give the operator the option to reduce energy to 200 Joules. This option will abort the charging sequence to the selected energy level and will instead stop charging when stored energy reaches 200 Joules. This option disappears when energy passes 200 Joules. There is no option to reduce energy to 300 Joules when charging to 360 Joules, only the option to reduce to 200 Joules appears on both 300 and 360 Joule energy selections. This feature is not present in manual mode.