The Pulse Oximeter Spo2 & Heart Rate Monitor is a reliable digital finger oximeter with infrared sensor technology. You will receive two devices in this bundle. The standard Adult SPo2 will require two AAA batteries and is designed for adults. The Peadiatric pulse oximitere is rechargeable and is supplied with a usb- charging cable to permit recharging from any mobile phone, tablet or laptop charger. The Peadiatric Spo2 is designed with children's fingertips in mind, it is light weight with a children's funny face design making it a little more suitable and bearable for them to tolerate. wide range of patients. Bith displays are digital and the power source again being batteries for Adult and rechargeable inbuilt battery with the Peads pulse oximeter.