High quality oximeter used for patient spot checks. This Oximeter reads in both directions with simply the touch of a button. It uses two AAA batteries (not included). Incredibly simple to use simple turn on and leave on the patient's finger for at least 10 seconds with the most accurate measurement after one minute. It has two modes, one for self use where the numbers appear toward the user and second mode if an HCP is utilizing it wherein the numbers appear in the direction of the secondary person. How an oximeter functions: The oximeter has two lights diodes one red and one infrared which flash and visible to a photo diode on the other side. The photo diode analyzes this light to read the amount of oxygen in your hemoglobin. This is a simple yet remarkable piece of technology!