Type 40

The Type 40 — or, formally, the Type 40 time travel capsule — was the class of TARDIS to which the Doctor's TARDIS belonged. (DW: Victory of the Daleks, The Pirate Planet, et al)

Little was actually known about the type, aside from the example provided by the Doctor's TARDIS itself. However, because he was prone to change the configuration of his machine — such as when he impulsively added a found tribophysical waveform macro-kinetic extrapolator for additional shielding (DW: Boom Town) — it was virtually impossible to say what the qualities of the standard Type 40 actually were, and how it specifically compared to other types.

The one quality on which most of the Doctor's Time Lord contemporaries agreed was that Type 40s were antiques. At one time or other, the Monk, the Master, and the Rani all described the Doctor's TARDIS as undesirably old. (DW: The Time Meddler, The Claws of Axos, Time and the Rani) Romana, likely the youngest of the Doctor's contemporaries, indicated that the type was no longer on the syllabus at the Time Lord Academy. (DW: The Pirate Planet) Indeed, once when the Doctor returned to Gallifrey, Commander Hilred called the type "obsolete" and noted that all had been pulled from service. (DW: The Deadly Assassin)

Another peculiar quality of the type was that they all were installed with the Record of Rassilon. (DW: State of Decay)