Each microphone plugged into the handset socket of a field telephone or switchboard. There were two, two-pin sockets in the sides of the microphone body to enable the operator to plug in a headphone (kopfhörer).
A neck strap held the microphone on the operator’s chest, for hands-free operation. The operator could then use both hands to manipulate the switchboard, fill out message forms, etc.
The back of the microphone has a clip for securing it to a tunic or great coat. The back cover slides off by turning a screw marked “öffnen” (open).
With the back cover removed, the microphone capsule can be accessed. A regular handset microphone capsule is used.
Various types of headphones could be used with the chest microphone. Single or double speakers were used. All headphones for telephone use had a special two-pin plug. The plug pins were closer together than plugs used on radio sets and armored vehicle intercoms.
The speakers for telephone headphones produce sound when an electro-magnet causes a steel diaphragm to vibrate. The magnet’s coils have a resistance of around 57 ohms. Radio and intercom headsets work the same way but have a much higher coil resistance… 2000 to 4000 ohms. They won’t work when connected to field telephone equipment.
Most WW2 German headphones sold by militaria dealers are for radios and intercoms. The dealers usually don’t list (or even know) what the headphones were used for. Some of the headphones are missing the plugs, so it is impossible to quickly tell if they were for field telephone use. Unless the dealer specifically states that the headphones were for use on field telephone systems, don’t buy them.
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