Support battery-only use, get rid of the trouble of power cord restricting the usage location. Perpetual calendar setting: January 1, 2000 to December 31, 2099 Time format 12HR/24HR display selection Week display in five languages: EN IT FR SP GE 2 alarm clocks can be set, with a default 5-minute snooze function 12 moon phases Indoor temperature display range: 0+50 & +14+122, display resolution: 0.1 & Indoor humidity display range: 20%RH95%RH, display resolution: 1%RH Outdoor temperature display range: -20+70 & -4+158, display resolution: 0.1 & Outdoor humidity display range: 20%RH95%RH, display resolution: 1%RH Temperature display format selection (/) Level 3 comfort display for indoor environment 433MHz ASK receiving OUTDOOR transmitter, maximum receiving 3 effective RF channels Outdoor temperature upper and lower limit alarm and frost point alarm function. Temperature and humidity trend display Recording of maximum and minimum indoor and outdoor temperatures Air atmospheric pressure display range: 850 hPa/mb1050 hPa/mb & 25.10 inHg31.01 inHg, display resolution: 1 hPa/mb & 0.03 inHg Air atmospheric pressure unit selection: mb/hPa or inHg Air pressure change records in the past 1 to 12 hours Histogram display of trend changes in barometric pressure over the past 1, 2, 3, 6 and 12 hours Five-level weather forecast: sunny, cloudy, cloudy, rainy, rain+snow 3-level pressure trend display When using only battery, the screen data can be read normally without backlight. You can also use the button to light up the backlight for 5 seconds When using the power supply mode, the backlight is always on or the backlight is turned off power supply: Host: 21.5V AA (battery not included in shipment) or USB power cable (included) Transmitter: 21.5V AA (battery not included in shipment)