Every time a TARDIS dematerializes it leaves behind a telepathic "thumb print" of the operator's Symbiotic Nuclei. These "thumb prints" make it very easy for the High Council of Gallifrey to track a TARDIS through Time and Space. Through extensive modifications it is possible to bypass the symbiotic relationship and distort the telepathic "thumb print," thus preventing a TARDIS from being tracked. To do so, a TARDIS's structure must be changed by installing controls and systems made of real matter and by drastically altering the operating system. This bypasses the Briode-Nebuliser, keeping it from automatically absorbing the Molecular/Dematerialization Codes from the operator's Symbiotic Nuclei.

These codes are essential for dematerialization and safe vortex travel. Thus to ensure an accurate trip the operator should input the codes manually. Usually this is done telepathically before dematerialization, but they can be permanently programmed into the console as well. These complex codes are kept secret from most Time Lords and are quite difficult to compute and memorize. Without this telepathic "coaxing" some TARDISes with a Symbiotic Bypass won't even dematerialize. Minor errors in the code will result in malfunctions in the Directional Unit, often leading to a misjump. When this occurs a TARDIS will emerge from the Vortex at the wrong point in space and time. It can take more than a dozen attempts to successfully navigate the TARDIS to a desired location. Another side effect of this system is that the Rassilon Imprimature isn't strictly required to initiate a space-time jump. The Symbiotic Bypass also allows a TARDIS a large amount of free will. Because of these side effects it is not unknown for such a TARDIS to allow any sentient that it "likes" to initiate a flight, assuming he has inputted the proper Coordinates.