Clément Ader, a French engineer already known for his telephone patents and for the Avion III, presents in 1897 the first string galvanometer: a fine metal wire suspended between the poles of a magnet, designed to detect at high speed the pulses of telegraphic signals on transatlantic submarine cables. The instrument's sensitivity was too low for clinical use, but it is the direct technical precursor that Willem Einthoven adapts in 1901-1905 to record the human electrocardiogram.