5)PR sound indication (wired equipment).
2)Low-voltage indication: the low power indication symbol appears when the voltage is too low to work.0 millimeters (H) x 32.FDA Finger Tip Pulse Oximeter SpO2 Blood Oxygen Meter PR Heart Rates Bluetooth introduction CMS50D-BT Pulse Oximeter is a portable equipment adopting advanced technology it mainly checks SpO2 and PR value through the finger which provides advanced non-invasive and scientific means for quantitative measurement of oxygen saturation.