Inizi '900, Tasto telegrafico Italiano per cavi sottomarini.
Early '900, 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 "