In “CIRCUL” APP, you can set the real-time alarm reminding function of turning on blood oxygen monitoring, and set the threshold of blood oxygen alarm. When the real-time blood oxygen is lower than the alarm threshold and lasts for several seconds, the alarm prompt sound will be issued. Using this function requires the mobile phone to be placed near the ring and the APP turns on the sleep monitoring mode. The Bluetooth connection between the mobile phone and the ring is normal. The blood oxygen alarm function is only used when the sleep monitoring mode is turned on.