Page 179 - The Secret War in the Italian front in WWI (1915-1918)

CHAPTER EIGHT

above mentioned wire may allow to listen to a telephone communication that takes place on the
intercepted mixed circuit.
The electromagnetic induction adds to this phenomenon, whereby the telephone current in the
circuit to be intercepted generates a current with similar variations in the wire designed for
listening . The effect of induction between metal conductors had been well-known and used for
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decades also to try to transmit wireless telegraphic signals .
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The Austrian Army began to use this kind of eavesdropping in 1915 on the Italian front where,
in Ronge’s words “starting from August the Intelligence Service added a new branch: telephone
interception of enemy conversations” .
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Almost at the same time, starting from September 1915, the Italians began to detect in various
areas of the front line, the possibility of listening enemy telephone communications. Systematic
interception and tests to investigate the phenomenon took place the following month, with little
delay compared to the same activities carried out by the Austrian.

alMosT sIMulTaneous dIscoverIes In The ITalIan arMIes
The first Italian interception took place, in September 1915, in Cadore, near Cortina d’Ampezzo,
between Tofana and Col Rosà, in Carnia, on top of Zellon-Rofel and in Val Dogna, in areas
manned by the 4 Army . By early October, some eavesdropping happened also at Batognica, in
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the Julian Alps, occupied by the 33 Division of the 2 Army. Other tests were conducted within
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the 3 Army.
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All those interceptions occurred by chance, during conversations between ordinary field telephones
connected by single-wire connections and return in the ground (mixed circuits). Systematic
eavesdropping tests started within the 4 Army, in the Cortina d’Ampezzo area, in early October
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“on the right bank of the Fiorenza creek” where, following the casual listening occurred the
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previous month, Lieutenant Ludovico Fabbri was able to perfectly listen to enemy communications
by modifying the telephone appliance, as shown in picture 8.12. Lieutenant Fabbri performed
other tests also at different locations .
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After first systematic investigations, the 2 Army made some defensive tests to select the types of
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entirely ‘metallic circuits’ without return to ground, capable to reduce the intensity of the ground

89 Documents of this period allow one to infer that personnel involved in the first Italian interception activities considered the
effect of currents in the ground more relevant than induction. This general assumption at the time of mixed circuits, changed
with the transition to entirely metal circuits.
90 In 1892, William Preece had performed communications between two independent wires intelligible from approximately 5
kilometres. Yet he was not able to find practical applications for his system due to the length of conductors, which was almost
equal to the length of the connection. Moreover, the effects of mutual induction were known, as in the case of telegraph and
telephone circuits installed on the same poles.
91 M. Ronge, Spionaggio, op. cit., p.178. Ronge never mentions telephone interceptions on other fronts before the date in
question.
92 Chief Inspector of STM, Comunicazioni telefoniche tra stazioni italiane e austriache (Telephone communications between
Italian and Autrian stations), ref. no. 874, 20 October, AUSSME, Series B1, 105S, Vol. 87.
93 L. Fabbri, Memoria delle Intercettazioni telefoniche svolte dal Tenente Lodovico Fabbri dall’ottobre 1915 al dicembre 1916
(Report of telephone interceptions carried out by Lieutenant Lodovico Fabbri since October 1915 until December 1916),
Florence, 20 January 1917, ISCAG, Coll.222.
94 As the right side of the picture, the interception circuit includes a simple telephone receiver positioned between two wires
of adequate length, each one connected to the ground.

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