Automated Protocol Epsilon Delta Rho

Automated Protocol Epsilon Delta Rho was a feature of the Doctor's TARDIS designed to allow the TARDIS to automatically respond to distress signals without the Doctor's input. When activating, it would be signalled by a siren noise and the letters "ΔΣΡ" or "ΕΔΡ" appearing on the TARDIS scanners before it dematerialised on its own. (COMIC: )

History
Upon entering the TARDIS after regenerating, the Fourteenth Doctor, whilst writing a letter, heard "a racket" coming from the TARDIS console. Finishing the letter, (PROSE: ) the Doctor approached the console, confused over the source of the noise, before recognising it as the protocol. He allowed it to take him to Wembley Stadium at the 1966 World Cup Final, where he discovered the distress signal was a trap set by the Daleks. (COMIC: )

Behind the scenes

 * In Liberation of the Daleks Part 1, Liberation, the TARDIS' screen shows the Greek letters "ΔΣΡ", meaning "Delta Sigma Rho", instead of the correct "ΕΔΡ". This error was fixed in Part 9, Deep in Hyperspace, in which the protocol is used again, displaying the correct "ΕΔΡ".