Animal-language translation circuits
From Tardis Wiki, the free Doctor Who reference
Animal-language translation circuits were a component of TARDISes. Marnal mentioned the animal-language translation circuits as one of the important parts of the Doctor's TARDIS that wasn't working. (PROSE: The Gallifrey Chronicles)
It would appear that this function was eventually repaired, as the Eleventh Doctor claimed to speak 'horse' (TV: A Town Called Mercy).
