Relative Dimensional Stabiliser

The dimensional stabiliser of a TARDIS (specifically one of the kind used by Mortimus) regulated the outer plasmic shell of the ship in relation to its exterior. By sabotaging Mortimus' dimensional stabliser, the Doctor made the inside of Mortimus' TARDIS the same size as the outside which meant that Mortimus could not squeeze in through the doors of his ship. (DW: The Time Meddler)

By using the dimensional stabliser of the Doctor's TARDIS, Drax and the Doctor reduced their own size. (DW: The Armageddon Factor)

At least after the Last Great Time War, the dimensional stabiliser was a large device activated by a lever, which helped in flight. (DW: Attack of the Graske)


 * On one occasion, space pressure reduced both the interior and the exterior of the Doctor's TARDIS to minute size, without affecting the passengers adversely. The space pressure may have possibily affected the ship's dimensional stabiliser, though the Doctor did not say whether it had or hadn't. (DW: Planet of Giants)