The center of every LightScribe disc has a unique code that, together with a sensor in the drive, allows the drive to know the precise rotational position of the disc. This, in combination with the drive hardware, allows it to know the precise position from the center outwards, and the disc can be labeled while spinning at high speed using these references. It also serves a secondary purpose: the same disc can be labeled with the same image multiple times. Each successive labeling will darken the blacks and increase image contrast (see drawbacks). Successive burns are perfectly aligned.