The Cylethian were an alien species from the planet Cylith.

They built distress beacons into their space ships. Once such a distess beacon was used an inter-galactic rescue team would be on it's way to the place the signal was sent from. However if it would be pressed on Earth it would take them about 100 years to go there, because Cylith was very far away. (PROSE: Day of the Clown)

Sarah Jane Smith had such a distress beacon in her attic at 13 Bannerman Road. (TV: The Day of the Clown)

Community content is available under CC-BY-SA unless otherwise noted.