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. Descriptions 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.