Pit phone
A pit telephone is a special telephone set , which is designed for the special conditions underground .
Due to their design, these devices are explosion and even firedamp proof . The loud chimes make them easy to hear even in the case of excessive ambient noise. Older models in particular are made of cast iron and therefore weigh around 15 kg. Technically, mine telephones do not differ from conventional telephones, which is why they can be connected to modern telephone systems without any problems.
Similar or structurally identical telephones were also used in other industrial companies or on the railroad (for example as a line telephone, in this case mostly with an induction crank).
Manufacturers of such systems are or were among others Fernsig Essen, Funke + Huster and Siemens & Halske . Fernsig Essen and Funke + Huster have now merged.
