This French Army Fullerphone was probably developed in World War 1 after one the
British Fullerphone designs. It seems to have had a telephone embodied and probably
a potentiometer. When preparing this page no other information was found as in a
German World War 2 datasheet ‘Kennblätter fremden Geräts, Heft 13, Nachrichtengerät’.
(Foreign Equipment Data Sheets, Volume 13, Signal Equipment. See also WftW Compendium
I am still looking for an original photo and name of this instrument, including further
information such as its circuit diagram.