This circuit is part of the TARDIS's Main Space-Time Element. TARDISes are built not to change history and this circuit is designed to prevent the operator from breaking the First, Second, Third, and Fourth Laws of Time. These protocols are not physical laws per se, but rather something built into the Governing Circuits of all Gallifreyan time travel technology.[/ref]
The Third Law of Time prevents anyone from travelling into Gallifrey's past, and ensure that a Time Lords personal time is always synchronized with Gallifrey's time. It also ensures that Time Lords will be synchronized when the meet outside of Gallifrey. In order for the Governing Circuit to function as it does, it's likely that TARDISes know significantly more about where they are going then their operator does. For example, they would need to know where other TARDIS and Time Lords have also travelled. To be effective, they would have to have the power to alter destination times to ensure that Time Lords never violate the Protocols of Linearity.
The Time Track Crossing Protection Protocol is a pre-set circuit that (in a normally functioning TARDIS) constantly prevents a TARDIS from crossing its own timestream by arriving before it left in the same general area. Due to the Blinovitch Limitation Effect, any time a TARDIS violates the 1st Law of Time by crossing its own time stream a large amount of chronal energy is released. This chronal energy can damage space-time. Some Type 40 TARDISes have faulty Protocol circuits that have unreliable connections, causing them to disengage and allow the TARDIS to break some of the Laws of Time.
Removal of the Relativity Differentiator will allow a TARDIS to travel into Gallifrey's distant past (before the Eye of Harmony), but it will prevent the TARDIS from changing its spatial coordinates relative to its current planet. The Temporal Limiter is also a key component of the Governing Circuit. A Temporal Limiter is required Vortex travel forward or backwards in time, and sabotage to it can effect the temporal aspect of a space-time jump.
It takes a major surge of power from the Prime Eye of Harmony to override this circuit (this must be authorized by the High Council). Despite this, a clever Time Lord will find these limitations easy to avoid. For example, the Time Track Crossing Protection Protocol can be overridden (though the operator then risks causing the TARDIS to vanish into a temporal nullity).
The following color code is used:
- Black: For information from the TV Series, including Dimensions in Time, and 1996 TV Movie.
- Blue: For information from the Novels and Audios including Target, Virgin, BCC, and Big Finish.
- Green: For information from 'licensed' reference sources such as the Technical Manual, Doctor Who Magazine, and the Role Playing Games.
- Red: For information from unofficial sources -The Faction Paradox series, behind the scenes interviews, author's speculation, and popular fan belief.
The TARDIS Technical Index is copyright Will B Swift.