The Wolo BA-500 measures the ambient noise level and instantly self-adjusts to produce a three-(3) decibel beeping sound louder than the surrounding noise. Automatically adjusts to a voltage range of 12-48 volt vehicles. The electronics are sealed in rock hard epoxy for protection against dust, vibration and moisture. The reinforced plastic housing has been designed for easy and secure mounting. Wire leads make installation easy. Designed for heavy-duty commercial industrial applications. Includes mounting hardware and warning decal. Instructions in English / Spanish.