Function: Measure indoor and outdoor temperature and humidity, Celsius and Fahrenheit conversion Maximum and minimum temperature and humidity memory function Can view historical temperature and humidity data Up to 3 outdoor units can be connected (with one transmitter, choose one-to-one order, and with three transmitters, choose one-to-three order) There are two high magnetic magnets on the back shell of the host, which can be adsorbed on metal objects There is a stand on the back of the main unit, which can stand in a horizontal position High sensitivity touch button control, easy to operate Time, alarm clock, snooze function Temperature and humidity trend indicator HTN large-screen high-definition angle-free color screen LCD display With backlight, automatically turn off the backlight after 30 seconds without operation The outdoor unit can be hung using the hanging holes, or it can be placed on a standing table The outdoor unit is XP4 waterproof (in order to keep the outdoor unit in good use, the outdoor unit should be placed vertically to avoid direct sunlight and direct rain for a long time) parameter: Indoor Temperature Range: -4F - 158F (-20C - 70C) Outdoor Temperature Range: -40F - 158F (-40C-70C) Humidity range: 20%-95% Temperature display unit: C/F optional (default is C) Temperature Resolution: 0.1C/F Humidity Resolution: 1% Refresh rate: 10 seconds. Error: temperature plus or minus 1C, humidity plus or minus 5% Wireless receiving range: 100 meters RF wireless frequency: 433 MHz time function 1 set of alarm clock snooze function Backlight function (backlight duration 30 seconds) Power supply: indoor unit: 3 AA batteries, transmitter: 2 AA batteries (regular delivery does not include batteries)