Spl-Lab Smart Voltmeter - is multifunctional digital car voltmeter. Although most of car electronics manufacturers state that their products have inbuilt protection from supply voltage sags or swells, in actual practice it turns out that not every, even expensive, amplifier is able to cope with this task. It means that another voltage overrun can end with expensive repairs or buying new unit. But if you add to your system an inexpensive device from Spl-Lab you can forget about such problems once and for all.