This is the secret that makes the Philips HeartStart FR3 AED so cost effective to own. Other AEDs use pediatric electrode pads for use on children. It means you'll have to regularly replace them just like adult electrodes pads. The FR3 uses a "key" that when inserted into the device, converts the FR3 into a pediatric defibrillator.
The key can be used over and over again with no need to replace it. Compare that to the cost of replacing pediatric electrode pads on other AEDs and you'll experience the savings. The HeartStart FR3 Smart Pads III are used for all emergencies.