The Redwood gazette. [volume] (Redwood Falls, Minn.) 1873-1940, 1921-12-28
PhOtO-PhOne the
Latest Invention
ILLINOIS UNIVERSITY PROFES-
SOR MAKES IMPORTANT. DIS
COVERY, is DECLARED.

Will the moving picture industry re-
ceive a revolutionary addition through
a scientific discovery made at the Uni
versity of Illinois, basic patents for
which are held by that institution? 1t
seems possible that this discovery will
make the movies of the future talk, so
that there will no longer be "the silent
drama"
The scientific discovery is that of
an extremely sensitive and reliable
"photo-electric CELL" made about two
years ago in the physical laboratories
of the University by Professor Jakob
Kunz. The incident is good exam
pie of the unexpectedness by which
some great discovery may be made
years in advance before it can be
practically used.
Device For Turning Flashes.
The photo-electric cell is a device
for turning flashes Of light into cleo
trio pulses and is so sensitive that it
reacts to light from stars which can
not be seen with the naked eye. Be-
cause of this extreme sensitiveness,
the photo-electric cell promises to dis
place the selenium cell which has been
used up to the present time in expert
ments carried on to produce speech
accompanying moving pictures.
A Swedish scientist has developed
device which he calls the photo
phone" by which such speech is more
or less perfectly produced. This is
done by having second film on the
same spindle as the moving picture
film, on which are photographed var
ious curves and openings correspond
ing to the words which are to accom-
pany the pictures. A beam of light
sent through this film falls upon a
selenium cell. The selsnium cell de-
pends upon a discovery made many
years ago that the metal selenium
changes it's electric resistance when
light falls upon it. 1t is thus possible
to get variations in an electric current
by letting the beam of light from a
speech photograph film fall upon such
cell. These variations act in tele-
phone to produce speech.
The Selenium Cell.
The selenium cell is much inferior
to DIR. Kunz's photo-electric cell IN
Transforming light waves into electric
pulses. The photo-electric cell is not
only much more sensitive, but it has
no lag; that is it responds immediate
ly to a light wave even after hours
and days of use. The selenium cell is
not only as sensitive, but it has the
disadvantage of having this lag, or
fatigue.
CDR. Kunz has been working for
several years on the effect of light on
certain Of the alikali metals, such as
potassium and sodium" said the head
Of the department. "a layer Of any
one of these metals when in vacuum
or certain low pressure gases gives off
negative electricity; that is, current
of electricity can be produced by let
ting a beam of light fall upon a film
Of potassium which is properly pre-
pared inside of an exhausted glass
bulb. The current passes across the
evacuated space to a loop of platinum
wire and thus to the outside circuit.
While this electric current is very
small, it can be amplifed by methods
which are we'll known today in cleo
tro-etchnics, and so the size Of the
current is no detriment to the use of
the photo-electric cell.
"Just as the little currents, which
were set up at Arlington Cemetery on
Armistice Day by President Harding's
voice were magnified and reproduced
thousands of miles away, so can these
little photo-electric currents be mag
nifed and produce sounds in loud
speaking telephones"
It is therefore logical to expect that
the scientific discovery of sensitive
and reliable photo-electric cell will be
used to give US the perfect photo
phone of the future. One large COM
pany is said to be already developing
such use of this photo-electric CELL