Regeneration unit The regeneration unit ( also referred to as the regeneration tank and regen disc by Thorne and Starkey respectively ) was a maintenance device implanted in robots such as K9 Mark I . Properties . Although designed to repair small fault , such as a faulty wire or a clogged gear , the device could build a new robot from the wreckage of the original . The unit ' s specialty was critical energy levels . Backup power was stored in the device to recharge the robot ' s powercore . Under certain circumstances , it could reconstitute a lost accessory with the excess power . If a robot were only an inch from death and the regeneration unit worked , the robot would be resuscitated . The reconstitution of lost accessories was a result of the default setting . The robot would be returned to its default state , as good as new . One was installed in K9 Mark I at some point prior to his transport via the Space - Time Manipulator to 21st - century Earth . History . When K9 was infected by the Swarm , he went into " self - regeneration " to recover . ( TV : " The Invisible Enemy " ) It is not known whether this ability was related to the regeneration circuit . After K9 self - destructed to defeat four Jixen warriors , Starkey retrieved the unit and K9 regenerated into a new body . Following regeneration , K9 remembered his name but couldn ' t recall additional details of his past ; memories of his adventures with the Doctor and Leela , his two former masters , appeared to be at least temporarily lost . ( TV : " Regeneration " ) Thorne and Lomax knew of the Regeneration unit and decided to acquire it starting with Thorne ' s failed plot to cause K9 to regenerate with the use of a suicide bomber . ( TV : " Robot Gladiators " ) They eventually succeeded , Thorne coming to Darius Pike with a proposal , not giving the requested component ' s name and calling it " the cybernetic equivalent of an appendix " . He had him try to convince K9 to agree into surrendering the device in return for his missing memory chip , promising Darius his father would be released from his imprisonment if he complied . K9 thought it a trick , although he couldn ' t resist the opportunity to discover his lost memories and accepted ; it turned out to be a trick . Thorne gave the unit to an unknown force . ( TV : " Hound of the Korven " ) The unit was contained inside the Trojan , a behemoth created by mixing together DNA from aliens encountered by K9 . After K9 depleted his energy banks to defeat the Trojan , the absence of his regeneration unit signalled his demise . However it returned to him just in time , recharging his powercore and giving him a new lease on life , reconstituting him completely . ( TV : " The Eclipse of the Korven " ) Behind the scenes . The regeneration unit prop had writing on it which resembled the Greek - and - mathematics text used to represent Old High Gallifreyan in the classic series of " Doctor Who " . Specifically , it contained the phrase " ∂³∑x² " , which was used to represent the Doctor ' s name in the first edition of the 1972 behind - the - scenes book " The Making of Doctor Who " by Terrance Dicks and Malcolm Hulke . This would seem to suggest that K9 ' s regeneration unit was installed by the Doctor . Bob Baker , K - 9 ' s co - creator and executive producer of the " K9 " TV series , said that the regeneration unit was " put there presumably by the Time Lord s , but of course we ' re not allowed to mention that . "