sentences:  The common 12-volt MR16 lamps, therefore, require a ferromagnetic or electronic transformer—sometimes misnamed as a "ballast"—to convert the 120- or 230-volt mains voltage to the extra-low voltage required by the lamp.Certain MR lamps can operate directly on the mains voltage.These lamps typically use a GU10 turn-and-lock base, so they cannot be accidentally interchanged with low-voltage lamps.