Away from the front lines, the majority of German field telephones were connected by single wire (Einfachleittung). Communications were via this single wire and ground (Erde). This required the use of grounding stakes, as shown in the illustration below.
WW2 German grounding stakes are commonly available from militaria dealers for a reasonable price. The stakes have a wire terminal on the side for connecting to the Lb/E terminal on, for example, an FF33 field telephone.
To connect to ground, the stake is driven into the soil. Quality of the ground connection depends on the type of soil and the depth that the stake is driven into the soil. Moist, black dirt soil is best. Dry gravel is worst.
Small holes are drilled along the shaft of the stake. There is also a small funnel-shaped hole at the top of the stake. To improve the ground connection, pour water into the hole at the top of the stake. This water will flow out of the holes along the shaft and into the soil around the stake.
Connect the wire from the stake to the Lb/E terminal on the FF33. Connect the wire to the other FF33 to the La terminal.
Follow the same procedure on the other FF33. You should now be able to talk between the two field phones.
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WW2 German Field Telephone Equipment 