Philips Philips FRx Infant and Child Key Overview The FRx uses a "key" that when inserted into the device, converts the FRx into a pediatric defibrillator. It is intended for use on children up to 8 years of age and less than 55 lbs. Delivers 50 Joules. Package contains 1 Key. MSRP: Was: Now: $111.00 Add to Cart