Page 229 - The Secret War in the Italian front in WWI (1915-1918)

CHAPTER TEN

Simple telephone equipment used during the first interception
activities were replaced by specific devices basically
structured as shown in picture 10.13. In January-February
1916, telegraphists of the 2 Army produced the ‘detectors
nd
of the 2 Army type’ along with a switching table for quick
nd
selection of the intercepting wires among the available ones .
78
Picture 10.14 shows the photographs of two portable detectors
of this kind including the switching devices, adopted in many
areas of the front .
79
In addition, in the course of 1916 the the Italians as well as
the Austro-Hungarians gradually adopted valve amplifiers ,
80
allowing higher receiver sensitivity needed to compensate the
reduction of the intercepted currents due to the replacement
of single wire earth return circuits (mixed circuits) with two-
wire circuits . In June 1916, upon returning from one of his
81
missions in England, Captain Guglielmo Marconi suggested
the application of a particular equipment to improve listening
in telephone interception. This device - most likely a valve
amplifier - was delivered to the Italian army because Marconi
was extremely busy with other experiments considered to be
more important and he could not attend to the tests personally .
82
10.14 Interception devices implemented In the autumn of 1916, the Telephone interception office of
by the 2 Army (ISCAG Archive) the 2 Army built the ‘amplifier - detector of the Gorizia type’
nd
nd
shown in picture 10.15 , using two triodes called ‘Gorizia
83
valves’ that were designed according to Professor Quirino Maiorana’s recommendations and
manufactured at an electric bulbs plant in Novi Ligure owned by engineer Giuseppe Longoni.
The ‘Gorizia valve’ was largely employed during the war for the radio-communications of the
Italian army and navy and included in Professor Giancarlo Vallauri’s famous experiments at the
Electro-technical and Radiotelegraphic Institute of the Navy .
84

78 A. Carletti, op cit., p. 17. The series condenser not only stops continuous currents or telluric currents, as well as other
disturbances generated by power supplies, telegraph currents, etc., but it also minimises the circuit impedance balancing the
headset inductance.
79 The picture is taken from G. Guasco, “Servizio d’intercettazione delle trasmissioni telefoniche” (Interception Service of
telephone transmissions), AUSSME, Series E1, env.111.
80 Supreme Headquarters, Office of the Chief of Defence, Fonogrammi di fonte austriaca, op. cit.; Chief Inspector of the
STM, Comunicazioni telefoniche, op. cit.
81 This replacement does not cancel all the causes of eavesdropping. Ground leakage caused by imperfect isolation of twisted
pairs, of insulators, etc. was difficult to eliminate in the uncertain conditions in war zones and generated currents in the ground
in addition to induction effects due to unbalanced current in the two wires.
82 Supreme Headquarters, Coordination and Deployment Office, Letter to the Ministry of War, Officer Personnel General
Directorate, Subject: Senatore Guglielmo Marconi, Ref. no. 24598 of 14 July 1916, ISCAG Library, G. Marconi folder. At
that time, Marconi was focussing on the mentioned revolutionary use of higher frequencies to increase, amongst other things,
the directionality of antennas.
83 A. Carletti, op. cit., p. 22. The name given to this equipment referred to the recent conquest of the city. Excluding valves,
Gorizia amplifiers were built in the electric laboratory of the 24 Telegraphist Company by servicemen with a background in
th
the State Telegraphic and Telephone Administration.
84 Vallauri’s tests verified an equation that expresses in an analytical form the electric behaviour of a triode valve. The Gorizia
valve was one of the valves used for this purpose.

227