The Tardis is an acronym for Time And Relative Dimensions In Space. A Tardis is a very complex time and space machine invented by the Time Lords. It is capable of transporting its operator to any position in time and space. It is dimensionally transcendental and is almost indestructible, because it has many forcefields and the facility to dematerialise out of any situation. As the Tardis design is constantly updated by the Time Lords, but the Doctor stolen Type 40 remains the only model of its kind still functioning. Access to the Type 40 is via the operator's isomorphic key which only responds to those programmed to use it, though with the Doctor's Tardis this is not always the case. Its most obvious malfunction is the chameleon circuit which should transform the appearance of a Tardis to blend in with its surroundings. The Doctor's machine jammed in Totter's Yard, England in the 1960's and has since retained the form of a London police telephone box. The exact size and structure of the tardis changes, as rooms are occasionally jettisoned (such as Tegans room and the Zero Room), the ship also contains two control rooms, endless passageways, a huge swimming pool, the Cloisters and a costume room. Other Tardises encountered by the Doctor included those used by the Meddling Monk, the War Chief and The Master.
