Telepathic barrier
From Tardis Wiki, the free Doctor Who reference
The telepathic barrier was a ring of six pylons which surrounded and suppressed the Ood Brain. The Brain subconsciously caused an Ood rebellion while focusing patience on Ood Sigma when Dr Ryder weakened the barrier to its minimum. The Ood told the Tenth Doctor and Donna Noble that "the circle must be broken", referring to the ring of pylons. Eventually the Doctor and Donna shut down the barrier. (TV: Planet of the Ood)
