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In
1884 began his studies around the electrical resistance and
conductivity of metal limature. And in the same year
discovered the properties of metal powders to buy a strong electrical
conductivity after several excitations as extra currents, electrical
shock, inductions electrostatic etc.. Based on this important
achievement and following the research carried in the field, Calzecchi
Onesti built the "tube
to
filings" that many years later, with the name "Coherer"
was used by
Marconi as a detector of electromagnetic waves in its first unit of
wireless telegraphy. This
appliance consists of a glass tube containing powdered nickel and
silver with traces of mercury, placed between two electrodes steel, in
a vacuum. When it is
hit by electromagnetic fields, the high resistance of powder, it
becomes relatively low and then loses conductivity for percussion
(decoherizzazione). |
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