The Infant/Child Key is for use only with the HeartStart FRx Defibrillator to treat an infant or child who is under 55 pounds (25 kg) or 0-8 years old. If you are uncertain of the child’s exact weight or age, apply the defibrillator without the Infant/Child Key. Once the Infant/ Child Key is inserted, the FRx automatically reduces the defibrillation energy and provides voice and visual instructions and CPR guidance specifically geared for treatment of infants/children. Graphics on the key show proper pad placement for infants and children.