A Motorcycle Headlight Modulator (or simply Headlight Modulator) is an accessory device that oscillates the intensity of a daytime-illuminated motorcycle headlamp at 240 cycles per minute (4 Hz). The intensity is modulated between approximately 20% and 100% of normal steady-burning intensity. The headlight operates at full intensity 50-70% of the time. US and Canadian regulations require headlight modulators to include a light sensor that disables modulation when the ambient light level drops below a certain point. When this happens, the headlamps burn steadily.
