Type 40

Type 40 was the class of TARDIS to which the Doctor's TARDIS belonged.

History
Mortimus said that while the Doctor had a Mark I, the Monk himself had a Mark IV. We do not know if the Type 40 belongs to a Mark I class of TARDIS or whether Type 40 had more than one Mark. Probably the latter, as the Doctor found the technology of his own TARDIS almost entirely compatible with the Monk's. Also, the central consoles of the two craft looked almost identical, although the Monk's ship had a slightly taller supporting column. (DW: The Time Meddler)


 * The Master also possessed a TARDIS of more advanced model, though we do not know of what type.

During the Doctor's third incarnation, The Master characterized the Doctor's Type 40 as 'overweight, underpowered; a museum piece!' (DW: The Claws of Axos), and by the Fourth Doctor's era all other Type 40s had been decommissioned (DW: The Deadly Assassin). Romana also noted the fact of the Type 40's obsolescence and referred to the Doctor's TARDIS as an antique vintage vehicle(DW: The Pirate Planet)

Opening mechanism
The opening mechanism of the TARDIS is very important. Without it the door is permanently locked. (DW: The Sensorites) The Doctor recently discovered that he can open the doors of the TARDIS by clicking his fingers even though he stated "it doesn't work like that". He was told this fact by River Song, who had observed a future Doctor opening the TARDIS that way. (DW: Forest of the Dead)

Desktop Theme
Alluded to by the Doctor, the desktop themes are what seemingly change the interior design of the console room from time to time, explaining the many different variations over the years. Amongst the themes are the standard grey and white column look of many early seasons, a Gothic look, a "leopard skin" look, and a "coral" look.(DW: Time Crash)

Primary function
The Type 40, of course, was designed for time and space travel via the Time Vortex. It used its dematerialization circuit to de-materialise and re-materialize at will into the Vortex. The Type 40 was actually designed to be operated by six pilots working as a team. When fully crewed, it is capable of remarkable feats, including towing an entire planet through time and space (DW: Journey's End).


 * It seems a testament to the Doctor's piloting ability then, that he could even travel at all. Though nearly a century's worth of personal modifications probably contribute to that

Conventional transport
It could hover in the air (DW: Fury from the Deep, Logopolis) or fly through space like an aircraft or spacecraft. While in this mode it often spun, like a top. (DW: The Runaway Bride, Doomsday) It could also land and float on water. (DW: Fury from the Deep) It was also capable of overcoming seemingly any amount of gravity, up to and including that of a black hole. (DW: The Satan Pit)

Limits
A properly piloted and working Type 40 was capable of transporting its occupants to almost any point in space and time. Before the Time War, a Time Spiral corresponding to the end of the Humanian Era prevented craft from travelling too far into the future (MA: The Well-Mannered War). Following the destruction of Gallifrey, some of the limits on travel seemed to be removed, as the Doctor's TARDIS travelled to more than five billion years CE without difficulty (DW: The End of the World, New Earth).

The TARDIS managed to travel over 100 trillion years into the future, beyond where any Time Lord had been known to venture. However, Captain Jack Harkness touched the TARDIS at the point of dematerialisation, which, according to the Doctor, caused it to jump to the end of the universe trying to escape him. (DW: Utopia)

A Type 40 could go out beyond the edges of the universe. (DW: Logopolis).

Unusual functions
Pressing an emergency switch, the Doctor found himself in the Land of Fiction (DW: The Mind Robber). The Doctor believed that his TARDIS could materialize inside areas of the psyche. (DW: The Chase)

Before the destruction of Gallifrey, the Doctor, using the console of the TARDIS alone, found himself in an alternative timeline (DW: Inferno). Later, the Doctor said that the death of the Time Lords in the Last Great Time War had made crossing between worlds almost impossible. (DW: Rise of the Cybermen)

Finally, though this happened by accident, the TARDIS could shrink itself and its occupants. (DW: Planet of Giants) In another, unrelated instance, it got inside a miniscope and shrunk on that occasion, too. However, this presumably happened because of the technology used by the miniscope itself. (DW: Carnival of Monsters)

Camouflage
The TARDIS' outer plasmic shell had the properties of a solid conventional object. (DW: Logopolis) With its chameleon circuit (DW: An Unearthly Child) (once called a cloaking device by the Doctor, DW: Doctor Who: The TV Movie), it could change shape. The TARDIS seemed to weigh roughly the same as the object it was disguised as, rather than manifesting the immense theoretical weight the interior possessed. On several occasions the Doctor's ship was picked up and moved using only manual labour (DW: Full Circle, DW: The King's Demons, Time-Flight). While resting on an uneven surface it could relatively easily be blown over by high winds (DW: The Curse of Peladon). On one occasion it touched down onto the North Sea as if buoyant, presumably by design, after having already touched there like an aircraft or spaceship. (DW: Fury from the Deep) The Doctor's ship was almost impervious to brute force attacks. The Doctor once stated to Rose that "the assembled hordes of Ghengis Kahn couldn't get throught that door". (DW: Rose). It was effectively indestructible likely due to the "shields", the one time these shields were down the Tardis collided with both an earlier version of itself and the Starship Titanic, the latter being seen to burst through the interior wall.(DW: Voyage of the Damned). However, the Sensorites were able to cut the lock out of the external shell, effectively sealing the vessel. (DW: The Sensorites)


 * Only the exterior of the ship was breached on that occasion. There was not a penetration through to the interior.

The immense gravity field generated by the Tractators on Frontios initially warped the TARDIS interior before actually ripping the vehicle apart. (DW: Frontios) A Voracious Craw would have been powerful enough to destroy the TARDIS completely. (NSA: Sick Building) Time Lord technology was also able to force entry relatively easily on a number of occasions.

The Doctor described his Type 40 on many occasions as sentient. Therefore some empathy must exist between the user and the machine. (PDA: Heart of TARDIS) During one crisis, the Doctor's ship caused its crew to panic and behave irrationally and to manifest clues as to the emergency, such as melting clocks. (DW: The Edge of Destruction)

Basic defenses and temporal grace
A hostile Zarbi could not enter the Doctor's TARDIS, as if the ship itself would not allow it. (DW: The Web Planet) When the Shadow attempted to do so, the doors of the ship flooded with blinding light and stopped him. (DW: The Armageddon Factor)

The Doctor claimed that the interior of the TARDIS existed in a state of temporal grace where the Doctor's enemies could not hurt him. The exact nature and area of this effect has varied. One account claims that within a TARDIS it is literally impossible to die from unnatural causes, with anyone so killed being instantly resurrected (PDA: The Infinity Doctors). More commonly, energy weapons were simply rendered inoperative (DW: The Hand of Fear, DW: The Invasion of Time) and even then the effect seemed limited only to the console room.

On many other occasions it seems that no such defense existed. Cybermen (DW: Earthshock, Attack of the Cybermen) and a Dalek, for example, have discharged their guns in the TARDIS. (DW: The Parting of the Ways) It was possible that the device causing the effect often malfunctioned. When asked about this exact situation, the Doctor simply remarked that things don't always work as they're supposed to. (DW: Time-Flight)

Lock
The Doctor initially stated that there were multiple tumblers within the single TARDIS lock presented to the outside world. There were a total of 21 tumblers, and insertion of the key into the wrong ones would cause the entire assembly to melt, barring access to the TARDIS entirely. (DW: The Daleks)

As mentioned previously, the Sensorites were able to cut the lock from the TARDIS' outer shell, sealing the ship until the lock could be reinserted. (DW: The Sensorites)

Sabotage by the Monk later badly damaged the original complex lock system, which the Doctor replaced with a much less sophisticated lock. (DW: The Daleks' Master Plan)

Another account shows the Doctor removing the lock, but having to first disconnect the time rotor. With the lock removed almost anyone could walk into the TARDIS. (EDA: War of the Daleks)

There is some evidence to suggest that TARDIS keys are not vessel-specific (the Doctor was able to use his own TARDIS key to enter the Rani's TARDIS. (DW: The Mark of the Rani)

Also, it can be assumed that the lock of the TARDIS has a lock-out function, disallowing anyone entry regardless of whether or not they have a key. (DW: The Dalek Invasion of Earth, Utopia)

Isomorphic controls
The Doctor claimed to Sutekh that the TARDIS has isomorphic controls which would work only for him and no one else. (DW: Pyramids of Mars)


 * However, characters other than the Doctor have operated his TARDIS, both prior to and after this serial. Possibly, the Doctor was lying. (This was confirmed in the Fifth Doctor story "The Bride Of Peladon").

Emergency measures
Type 40s had many defensive devices, designed not only to protect the occupants, but also the ship itself. They included the HADS system (Hostile Action Displacement System) (DW: The Krotons).

It was also capable of "anchoring" itself onto another ship to not only stabilise itself, but also to allow the occupants to escape in the event of terminal instability ("break-up") This is invoked by an automatic safety cut out. (DW: Terminus)

Eye of Harmony
The Doctor's TARDIS had a (symbolic?) link with the Eye of Harmony and so derived its power from there. (DW: Doctor Who: The TV Movie)

Matter-energy conversion
The ship had, at one time, an ancillary power station, which on the Doctor's TARDIS existed in the form of an art gallery, the exhibited works apparently being converted from matter into raw energy when required. (DW: The Invasion of Time)

The TARDIS's architectural configuration controls could also delete rooms, apparently converting them and their contents into raw energy which was then dumped into the reactor core. This action could give the TARDIS the added thrust it might need to escape from areas of gravity strong enough to otherwise defeat the TARDIS's helm controls. (DW: Logopolis, Castrovalva)

Temporal rifts
After the destruction of Gallifrey, the Doctor recharged his ship with the energy from a temporal rift, in this case, the Cardiff rift. (DW: Boom Town, Utopia (TV story))

Other means
Once separated from the main universe on Pete's World the Doctor's Type 40 "died". After finding a glowing green crystal, the Doctor breathed on it, giving it, he said, ten years of his life. Within twenty-four hours, he said the TARDIS had enough energy to return home. (DW: Rise of the Cybermen)


 * We do not know how or why the Doctor's TARDIS lost its power when separated from the main universe. It may have something to do with the Doctor's new method of fueling it with the energy from temporal rifts
 * The Doctor does state that the TARDIS draws its energy from the universe, so being outside the "proper" universe cuts it off from that energy. He likens it to using diesel fuel in a petrol engine.

Required elements
Elements needed for the proper functioning of the Type 40 and requiring occasional replenishment include mercury used in its fluid links (DW: The Daleks, The Wheel in Space) and the rare ore Zeiton-7. (DW: Vengeance on Varos)

When the Doctor's TARDIS accidentally visited a parallel universe, it could not take its crew back immediately because its energy supply stemmed from the universe it was created in, so by removing it from its home universe its "life" energy supply was severed. (DW: Rise of the Cybermen)