The building was designed to appear as an oversize Diaphone resonator. The stop is unique, because it is a reed/diaphone hybrid. The siren was replaced by a diaphone in 1926. In 1928, the steam whistles were replaced by a modern air diaphone. In 1935, an air diaphone supertyfone sound signal was installed. A diaphone fog horn is attached. The steam sirens were replaced with a Type F-2-T diaphone (be-you) type signal in 1936. Many Gamewell diaphone systems remain in use today. The majority of diaphone installations were removed or became disused during the 1960s and 1970s. In 1926 they were replaced by Type F diaphone fog horns. The Poe Reef diaphone fog horn is still in current service. The diaphone is a unique and uncommon organ pipe. The diaphone sounded three blasts every two minutes. The Gamewell diaphone has a range of about six miles () under optimum conditions. Diaphone horns were placed on top of the fog-signal room from 1935 to 1960.