Shows range of Blood Oxygen (SpO2) measurements for yesterday and so far today (as recorded on your Apple Watch).

No longer used for communications (except by amateurs) morse code is used to identify beacons and repeaters

Squawk codes (four numeric digits) are issued by Air Traffic Control to help identify and aircraft on radar displays - they can also be seen on flight tracking apps such as Flightradar24. Note some special (pilot-selected) codes: 7500: Hijack; 7600: communications lost; 7700: general emergency (such as fuel low, medical issue, engine failure, structural damage); 1200: default for VFR in US/Canada; 7000: default to VFR in Europe

Q Codes originated in the morse code age when used for brevity; many have been retained in aviation; those presented here are searchable by code or content.

The phonetic alphabet is used to help receiving stations understand a message or call sign.

Callsigns are used in aviation and marine communications to identify the craft involved (for example, British Airways pilots use 'Speedbird' in front of their flight number