Nightrotor unit
From Tardis Wiki, the free Doctor Who reference
Nightrotor units were Dalek secret weapon present on every Dalek flying saucer, though only in its experimental stages. The point of them was to somehow reduce lightbeams, plunging into darkness the planets revolving around the sun which the unit was turned upon. Little was known about the weapon to humans, though they were aware of its existence. (NOTVALID: Inside a Skaro Saucer)