OLLGEN Multifunctional 4 in 1 Car Digital Clock In/Out Thermometer Voltage Monitor with Stand and Magic Tape Portable and mini design, plug and play, easy to use and accurately measure. NOTE: If the power is supplied by the car cigarette lighter when plugged ,backlight will light up and all the functions(including the time,temperature and volt ) will be displayed on the LCD Screen.  If the power is supplied by backup battery when unplugged ,it will not have backlight and lcd screen will display the time ,outdoor & indoor temp only. It means if you use this item by backup battery in the daytime ,you may not be able to see  and  switch clealy . Date/Hour, Week/Sencond display, switch the display between 12-hour and 24-hour, inside and outside Celsius/Fahrenheit temperature reading, swith temperature display between  and ( Press "DOWN" Key ). NOTE: OG is orginal Green and BU is Blue backlight, there are two colors of backlight for switch,  you can choose the backlight as you like(Slilde the switch to the side of the color which you like). Snooze and Alarm Function,Outside sensor with 6.6 feet cable, warns driver of black-ice conditions by alarm.Press "DOWN" Key 2 seconds , it will turn on the outdoor Freeze-Alarm .