The Navy gave Edison the use a
vessel and during the summer 1917 cruised the Long Island
Sound testing his listening devices.
Several other teams engaged the same line research
. Employing technology that had been developed
for the phonograph and telephone, Edison constructed simple
listening devices based phonograph reproducer attached to
a long speaking tube which was connected amplifying
device board ship. All the locaters then under
development could not distinguish between the noise a
submarine's screws and the background noise the search
vessel screw's and water turbulence.
Edison gave trying locate submarines distance
and concentrated detecting torpedoes they came close to
merchant ships. The problems Edison faced were increase
the scale the technology and work for corresponding
increase sensitivity. devised induction balance achieve
this end but was not sensitive enough. Much this experimental ground had been
covered the disc experiments and the development special
dictating machines. Edison
found out that the problem this type locater that
conditions are never perfect.XII- 8
changes magnetic fields caused its metallic bulk passing
through the water. The idea was good— it
is the basis excellent modern submarine locater— but the
right technology was not available.The listening device was
placed the water about feet from ship and perfect
conditions could detect submarine 5000 yards
