distress signal
From Trekipedia
File:alert red-tos-08.jpg
Red alert[1]
"Old style" distress signals were keyed to cause interference and attract attention. When the U.S.S. Enterprise NCC-1701 intercepted an old style distress signal in 2254, it caused the ship's systems to react as though a solid object was approaching, setting off collision warnings and the red alert klaxon.[2]
