Telegraph
From Tardis Wiki, the free Doctor Who reference
- You may be looking for the messages sent by telegraphy.
Circa 1900, at Fang Rock, there was an example of an early Marconi wireless telegraph, able to "send messages a long way". (TV: Horror of Fang Rock, PROSE: Doctor Who and the Horror of Fang Rock)
The Doctor gave a space-time telegraph to the UNIT, to be used to summon him to Earth in the case of an emergency. (TV: The Day of the Doctor)