There are a number of ways diaphones are represented in literature. Installations in Europe generally used single-tone diaphones. The group were signed to Grudge/Universal/BMG, to reissue "Diaphones" in 1997. This company still exists, although it no longer manufactures diaphones. Diaphones can instead be represented with double slashes. Dual diaphones were provided for a fog signal, as well as a bell and radiobeacon. Diaphones were powered by compressed air and could emit extremely powerful low-frequency notes.