Philips HeartStart FRx Trainer simulates how the HeartStart FRx Defibrillators will operate during a real-life sudden cardiac arrest event. Clear, confident voice instructions that provide easy-to-follow directions, and preconfigured scenarios, make training students easier. And for safety, the HeartStart FRx Trainer is sufficiently different to avoid inadvertent use in an emergency. Uses 4 "AA" batteries (not included).