fire alarm vs smoke signal

fire alarm

noun
  • The sound or other warning made by a fire alarm. 

  • An electromechanical or electronic bell, klaxon, chime, horn, speaker, strobe light or other device which warns people in a building of a possible fire or other condition requiring evacuation. 

  • An emergency response to a fire by the fire department with manpower and equipment. 

smoke signal

noun
  • A type of flare or combustion device sometimes used as a distress signal. 

  • A method of long-distance communication sometimes used in ancient and undeveloped societies, consisting of messages conveyed by means of columns or intermittent puffs of smoke. 

  • A message or sign sent by this method. 

  • An indirect message or indication, especially concerning a future event. 

How often have the words fire alarm and smoke signal occurred in a corpus of books? (source: Google Ngram Viewer )