"Barometer & Altimeter: The air pressure value on the screen corresponds to the air pressure at the current location. The height value on the screen is the sea level of the current location. Press the [ALTI/+] button to toggle the use of the altimeter and barometer.Relative Altitude: Monitor the ascending or descending altitude from a certain location or the altitude relative of a mountain or object, etc. Weather forecast: In addition to detecting altitude, the barometer also helps predict the weather for the next 12 to 24 hours based on on changes in barometric pressure. The effective range is 30-50km.History altitude record: Press [HISTORY] button, you can view the altitude and air pressure records of the history. It will show the most previous record in this mode, then you can press [ALTI/+] or [-] button to view history records forward or backward. It can record most 256pcs records, the distance of records is five minutes and you can change the distance from 1 to 60 minutes if you hold the [HISTORY] button for 2 seconds.Design Power saving: When you don't want to use the device, press and hold the [SET] button for 5 seconds, the device will stop all displays and enter sleep mode. And then you press any button, it will resume previous display. Backlight: In any mode, it can give you backlight for 5 seconds when you press any button. Product Description Materials: ABS Historical altitude record: 256-piece record Thermometer: Celsius/Fahrenheit format Clock: 12 hour or 24 hour format Calendar, backlight Design Power Saving: Start automatic altitude measurement Power:1 CR2032 3V battery (battery included) "