Diaphone

The diaphone was a noisemaking device best-known for its use as a foghorn: it could produce deep, powerful tones able to carry a long distance. Diaphones were also used at some fire stations and in other situations where a loud audible signal was required.

History

The diaphone horn was based directly on the organ stop of the same name invented by Robert Hope-Jones, creator of the Wurlitzer organ. Hope-Jones' design, based on the vibrations in air created by a slotted piston moving within a correspondingly slotted cylinder, was adapted and patented by Professor John Pell Northey of Toronto University, who added a secondary compressed air supply to the piston to power it on both forward and reverse strokes and create an even more powerful sound. The entire horn apparatus was driven by a compressor.

A diaphone being tested by an employee of the United States Coast Guard.

To manufacture the new equipment, Northey set up the Diaphone Signal Co. at Toronto in 1903.^[1] It manufactured a range of diaphone models: the large "Type F", which created a tone of about 250 hertz, found worldwide use as a fog signal, especially in lighthouses. The mechanism of the diaphone created a noticeable low-frequency "grunt" at the end of each note produced, caused by the speed of the piston reducing as the air supply was cut. As this low-frequency sound could carry further, Northey's son Rodney redesigned the "Type F" model to sustain the second low tone, creating the familiar two-tone fog signal which was commonly used in lighthouses and lightvessels in the United States and Canada (as well as in a famous series of radio commercials for Lifebuoy soap). Installations in Europe generally used single-tone diaphones.^[2]

Building housing the two diaphones of Split Rock Light.

Rodney Northey sold the Diaphone Signal Co. in 1932, when it was bought by a Buffalo, NY company, Deck Brothers, working under contract for the United States Lighthouse Service.^[3] This company still exists, although it no longer manufactures diaphones. The European manufacturing rights were obtained by Chance Brothers of Birmingham in the United Kingdom, already a major supplier of Fresnel lenses and other equipment to lighthouse authorities.

The majority of diaphone installations were removed or became disused when lighthouses were automated during the 1960s and 1970s, though a few survive in working condition in lighthouses around the world.

The Gamewell Diaphone

This considerably smaller device was produced by the Gamewell Corporation, of Newton, Mass, for use as a municipal alarm, especially at fire stations, to alert firemen and the public during emergencies. Many Gamewell diaphone systems remain in use today.^[4] The Gamewell diaphone has a range of about six miles under optimum conditions.^[5]

Working diaphone installations

The following installations are still functional and are demonstrated from time to time as tourist attractions.

• Duluth South Breakwater Lighthouse, Duluth (MN): the F-2-T (two-tone) diaphones at this lighthouse were reinstated after a campaign by residents, and reactivated in 1995.^[6]
• East Brother Light Station, Richmond, CA^[7]
• Grand Traverse Lighthouse, Michigan
• Low Head Lightstation in Low Head, Tasmania possesses the last working Type G diaphone (one of the largest models constructed) in the world. It has a range of up to 20 miles.^[8]
• Portland Bill Lighthouse, Isle of Portland, United Kingdom: A Type F diaphone decommissioned in 1996, but restored in 2003 for the benefit of visitors.^[9]

References