Sub-Wave Network

The Sub-wave Network was a piece of sentient software programmed to find anyone who could help to contact the Doctor. It used sub-wave communication to transmit, which means it is undetectable as it is below normal waves. It was created by the Mr Copper Foundation and further developed to Great Britain's former Prime Minister Harriet Jones.

The network found Jack Harkness at the Torchwood Hub, Sarah Jane Smith at 13 Bannerman Road and Martha Jones at the house of her mother in London. It also found Rose Tyler at Donna Noble's house but se was unable to communicate with anyone since the laptop she was using did not have a webcam.

As Martha Jones' superphone temporarily did not function, Torchwood 3 used the power of the Cardiff rift, Sarah using Mr Smith and using every single telephone on the planet to call the Doctor, they managed to get through to the TARDIS so that he could find where the Daleks had taken Earth. (DW: The Stolen Earth)