of the wail of a lost soul, the moan of a bottomless pit and the groan of a disabled elevator." One of the first automated fog bells was the Stevens Automatic Bell Striker. Some later fog bells were placed under water, particularly in especially dangerous areas, so that their sound (which would be a predictable code, such as the number "23") would be carried further and reverberate through the ship's hull. For example, this technique was used at White Shoal Light (Michigan). This was an earlier precursor to RACON. Diaphone From the early 20th century an improved device called the diaphone, originally invented as an organ stop by Robert Hope-Jones, and developed as a fog signal by John Northey of Toronto, became the standard foghorn apparatus for new installations. Diaphones were powered by compressed air and could emit extremely powerful low-frequency notes. In 1982, the Dutch broadcaster VPRO aired a live foghorn concert on national radio composed by Marnie Bjornson, relaying the sound of the foghorns in Emden, Calais, Nieuwpoort, Scheveningen, Den Helder, Lelystad, Urk, Marken and Kornwerderzand, mixed with studio music by sound artist Alvin Curran. Obsolescence Since automation of lighthouses became common in the 1960s and 1970s, most older foghorn installations have been removed to avoid the need to run the complex machinery associated with them, and have been replaced with electrically powered diaphragm or compressed air horns. Activation is completely automated: a laser or photo beam is shot out to sea, and if the beam reflects back to the source (i.e. the laser beam is visible due to the fog), the sensor sends a signal to activate the foghorn. In many cases, modern navigational aids, including GPS, have rendered large, long-range foghorns completely unnecessary, according to the International Association of Lighthouse Authorities. Railway fog signals Fog signals have also been used on railway lines since the middle of the 19th century to indicate to the driver of a moving train that a broken down train, a work party, or some other unforeseen hazard is on the line ahead. Small explosive detonators or torpedoes are placed on the track, and detonated by the pressure of the wheels of the oncoming train. The loud report of the explosion provides the indication to the driver, which, in most cases, requires the train to be stopped immediately. During World War II, these devices were modified to detonate demolition charges during railroad