TARDIS tracer


 * You may be looking for the tracer used to find the segments of the Key to Time.

The tracers were components in the Doctor's TARDIS. When the Doctor arrived on the planet of the Sevateem instead of in Hyde Park, he suggested that the error could be due to a nexial discontinuity and remarked that he must remember to overhaul the tracers. (DW: The Face of Evil)