As stated in a previous article, one of the considerations in building field telephone lines is providing a good ground connection. During WW2, away from the front lines, it was standard practice for the Germans to build field telephone lines with a single wire/ground connection. The “La” terminals were connected to the single wire, and the “Lb” terminals were connected to a grounding stake (Erdleitungsrohr).
In many cases, the soil was moist to more than 30cm in depth, and a good conductor of Earth currents (Erdströmen). As longs as the grounding stake was driven into the soil straight and to a good depth, the phone connection would be reasonably clear.
If the soil was dry, conductivity could be improved by pouring water, preferably urine or saline solution, into the funnel at the top of the stake. The liquid leaks out of little holes along the length of the stake into the soil.
If a grounding stake was unavailable, a K98k bayonet (Seitengewehr) could be used, although it is unclear how the bayonet was wired to the “Lb” terminal.
If the soil consisted of, for example, dryer sand (trockner Sand) then Earth current conductivity would be poor. Conductivity could be improved by digging a hole until moist soil (Boden wird feucht) is reached. A ground stake is then driven into the moist soil.
Sometimes the soil is a poor conductor of Earth currents no matter how much liquid is poured into the grounding stakes or how deep down a hole is dug. In this case, the Nachrichtentruppen had to make an Earth plate (Erdplatte). The plate could be made from a metal sheet, burst open tin can (Konservenbüchse), barbed wire (Stacheldraht), or wire mesh (Drahtgitter). The plate is connected to the “Lb” terminal by a wire. The wire is soldered to the plate.
The Earth plate is buried in a hole in contact with as much soil as possible to minimize resistance and improve conductivity.
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WW2 German Field Telephone Equipment 