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1868 The company was founded at the start of Government legislation for domestic telegraph companies and had a joint purse arrangement with the Eastern Telegraph Co . It was meant to succeed the Electric and International Telegraph Co. The company was registered in April, with the intention of completing a line between London and Calcutta. The cable would extend from Lowestoft and via Prussia, Berlin, West Prussia, Russia, Warsaw, Odessa; on through Persia to the Gulf, then sub-marine to Karachi, across India to Calcutta and then on to the Gulf of Bengal. 
The Siemens family were a major factor in the IETC and involved their three manufacturing companies, in Germany, Russia and London and used their influence to obtain the relevant concessions.
The line from London to Calcutta was to be 6,900 miles long.
1870 The cable was almost immediately broken by an earthquake in early July. It had to be replaced by a coastal land line during the following year.
After two years of construction, the circuit to Calcutta was completed in April. Messages could be sent from any office of the Electric and International Telegraph Co or from the offices of the Company to Calcutta, Bombay, Madras and all places west of Chittagong. Messages reached Teheran by automatic relay in just one minute; Calcutta was reached in twenty-eight minutes.
Apart from the halt to operations due to the First World War and its aftermath, it was in continual operation until the concession in Persia ended in 1931.
1931 The wires were then abandoned.
Siemens’ engineering was so substantial that its iron posts, still with three iron-capped insulators on each, were visible on the Caucasian coast and in the Persian desert over a century after they were installed.