Complex sentence: When the device is turned on, the sensor relays information about breathing patterns and rate, from which the device advances a melody (heard through the earphones, with visual cues on the LED screen) comprised of two tones.
Split into simpler sentences: When the device is turned on, the sensor relays information about breathing patterns and rate. The device plays a melody (heard through the earphones, with visual cues on the LED screen) comprised of two tones.