Emergency Program One

Emergency Program One was a feature of the Doctor's TARDIS designed to return a companion home in case of extreme emergency. (TV: The Parting of the Ways)

The Tenth Doctor mentioned that Emergency Program One was automatically activated after five hours. (TV: Silence in the Library) He also said that the program would activate if anything happened to him. (COMIC: The Time of My Life) When activated, it projected a hologram recording which explained the program. (TV: The Parting of the Ways)

Usages
Believing that he would die on the Game Station, the Ninth Doctor used it to play a message for the benefit of Rose Tyler before the TARDIS returned Rose to the Powell Estate in 2006. He activated the program by pointing his sonic screwdriver at the TARDIS. (TV: The Parting of the Ways)

Donna Noble recorded a message on it as a way to say goodbye to the Tenth Doctor, in the event that she might not have a chance to do so herself. (COMIC: The Time of My Life)

The program was tripped by the Tenth Doctor when he tried to get Majenta Pryce to Panacea. It was then co-opted by Finn Dargo, who used it as a way to effect an arrest on the TARDIS' inhabitants. (COMIC: The Crimson Hand)

Behind the scenes
The term Emergency Program One is first heard in dialogue in the television story The Parting of the Ways, where its spelling is not shown on-screen. It later appears in the comic story The Time of My Life, where it is spelt Emergency Programme One, despite British English using the "programme" spelling for television broadcasts and theatre information leaflets, not computer programs.