12 volt. Flashes the vehicle stop lights under emergency braking. The microprocessor control unit, triggered by the inertia switch at a deceleration of 6m/s2, flashes the vehicle stoplights at 3.5 flashes per second for up to 12 seconds, warning following vehicles of emergency braking. After 12 seconds, or when emergency braking ceases, the brake lights revert to normal operation. ECE approved.