Radio
Radios were communication device that transmitted or received sound over a short distance using radio waves. They were mainly used by Humans on Earth.
Radios were usually used to play music that people could dance, sing and "fall in love" to. To Daleks, however, a radio was just noise. (DW: Evolution of the Daleks)
In 1938, Orson Welles broadcast a radio play adaptation of The War of the Worlds. (BFA: Invaders from Mars)
Circa 1969, radios manufactured by International Electromatics played a part in the Cybermen's plans to invade Earth. (DW: The Invasion)
Research stations used radio waves for tests and often transmitted them out into space to search for signs of intellegent life. In the 1970s, the Nestenes attempted to materialise on Earth through radio waves at one station, but they were stopped by the Doctor and the Master. (DW: Terror of the Autons)
Radio transmitters were a form of communication. (DW: The Sea Devils)
