The term FOGHORN can be broken down into two crossword solutions: DIAPHONE (8 letters) and SIREN (5 letters). A diaphone is a type of foghorn that uses compressed air to create a loud sound. It is commonly used in lighthouses and other maritime locations to warn ships of nearby hazards. A SIREN is an auditory warning device that produces a loud, high-pitched sound. It is often used by emergency services such as police, fire, and ambulance to alert people of danger.