Anti-dreaming device

The anti-dreaming device, (TV: Snakedance) also known as the sleep induction box (AUDIO: The Cradle of the Snake) or dream inhibitor, (PROSE: The Dreaming) was a contraption devised by the Fifth Doctor. The device used an earpiece that when worn, cancelled out the brainwaves associated with dreaming. The Doctor had Tegan wear it to stop her dreaming of the Mara. (TV: Snakedance)

The Eleventh Doctor later developed several dream inhibitors to keep the Mara's control from worsening over its victims. (PROSE: The Dreaming)