HeartStart AEDs are designed to meet the needs of their users. Philips' shock is highly effective, yet gentle to a fragile heart...or the heart of a child. HeartStart OnSite (HS1), the only over-the-counter public access AED, features proven ease of use for lay responders. HeartStart FRx is easy to use and more rugged, featuring an easy transition between adult and infant/child mode.