The bicentennial history of the electromagnetic telegraph (from Ørsted’s experiments to social networks)

In 1820, Hans Christian Ørsted noticed the influence of electric current on the deflection of a magnetic needle. This discovery became the theoretical basis for the creation of electromagnetic telegraph. This review describes the previous methods of transmitting information. The contribution of Russian and foreign inventors to the development of telegraph communication, as well as the current state of this technology, is considered.