Early '900
Tasto telegrafico Italiano per cavi sottomarini.
Italian submarine telegraph cable key

Comment from W1TP Tom Perera: " That is a wonderful Italian Submarine telegraph cable key. These submarine telegraph cable keys are very rare because there were only a few cables that went underwater from one country to another and so few such keys were made. The story of these keys is complicated. The cables were very long and acted like BIG capacitors. This slowed down the rate at which dots and dashes could be sent.  To speed this up, One key was used for dots and it put a POSITIVE (+) voltage on the submarine cable. The other key put a NEGATIVE (-) voltage on the cable. The positive and negative voltages worked against each other and this speeded up transmission. See my submarine telegraph cable keys number 190 and 192 in: http://w1tp.com/m1000.htm  and numbers 1010 - 1015 in http://w1tp.com/m3000.htm   and my diving expeditions to recover the cables: http://w1tp.com/mcable.htm "
 

On the knobs:

Note the use of capacitors C1 and C2

Alcune immagini da   " CAVI TELEGRAFICI SOTTOMARINI " Hoepli 1895, prima e unica edizione:
- Macchina di Posa 
- Scandaglio propedeutico alla posa dei cavi 
- Recupero cavi dai fondali
- Tipologie costruttive dei cavi sottomarini
- Officina cavi telegrafici sottomarini di "Spezia"

Altro:
- Carico sul vascello Great Eastern ( Grande Oriente) della gomena telegrafica dell'Atlantico
 

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