4 in 1 designed: clock, indoor and outdoor thermometer, voltmeter, frost alert. Supply car power and built-in memory battery which can continue to work without backlight after power off, supply car power. Indoor\/outdoor thermometer: can choose Fahrenheit and Celsius mode, with range of -50? - 70? \/ - 58? - 158?. Digital clock: 12 \/ 24 hour mode choose. Small and easy to install in your car, large LCD display and blue\/orange backlight makes it easy to see. s Display: Widescreen LCD; Blue and Orange backlight choose; Clock function of: Calendar: day and date 12 \/ 24 hour mode; Snooze function alarm clock and 5 minutes, snooze time: 5 minutes; Thermometer function: Adjustable degrees Fahrenheit and Celcius(?\/?); Outdoor and indoor temperature monitoring; Exact temperature: 1.0? Duration of temperature measurement: 60 s Voltmeter function DC: 12V Key functions: Time: change day and date. Press 2s to enter the time setting state; ALM: show alarm time. Press 2s to enter alarm setting state UP: key up + 1. Under set alarm state, press to turn on\/off the alarm sound. SNZ: Set snooze DOWN\/?\/?: key down -1, passage between ? \/?. Press 2s to activate the outdoor freeze-alert. What's in the box: 1 x 4 in 1 car tester.