The Archangel Network was a series of 15 satalites put into orbit aroung the Earth and was diguised as a mobile phone network. It was, however, transmitting a telepathic field keeping the population of Eatrh in fear of the Master. The Doctor 'tuned himself into' the Network, and Martha travelled the world telling the story of The Doctor. Every one on Earth, thinking the same thing at the same time, 'Doctor', helped the Doctor rejuvenate and ultimatley stop The Master