Emergency unit

The emergency unit was a part of the TARDIS which, according to the Second Doctor, "move[d] the TARDIS out of the time-space dimension — out of reality". He once reluctantly used it to avoid lava that was approaching the TARDIS on the planet Dulkis. Consequently, the TARDIS was instantly removed from time and space, rendering all the TARDIS' instrumentation dead. (DW: The Mind Robber)