The HeartSine samaritan PAD 500P Defibrillator combines the very best in public access AED technology. Offering the unique CPR feedback technology, the 500p gives real-time feedback to the rescuer thus maximising the chances of survival! In making a decision as to which Automated External Defibrillator (AED) to purchase, you need to carefully consider the 4 links in the internationally accepted chain of survival - otherwise your investment might be an unwise one.