Through line-by-line scanning of a message written with special ink on a metallic surface, electrical impressions of the original and a telegraph circuit
could be used to transmit the information at a distance.
In the beginning the "hotline" was not a telephone, but rather teletypes and a duplex wire telegraph circuit
. (Indeed, in the beginning there was no voice element at all, over worries that verbal communications could easily lead to misunderstandings and potential gaffes).
In what seems to prefigure the inexorable rise of the mobile phone and global communication by at least seven decades, he added: "Wireless telephone and telegraph circuits
will span the world.