Palisadian., 1925-07-17

of

For the actual operation of the
transmitter. the picture, printed matter
or whatever is to be sent. is first photo
graphed on an ordinary camera film.
This is developed and then placed on
a glass cylinder, being held firmly in
place by metal clips. The picture Is
now ready to be transmitted.
Inside this glass cylinder is an in
candescent lamp, the light from which
Is focused in minute beam onto the
film as the cylinder is set in motion.
AS the light and dark portions of the
picture are traversed by the light
beam, the intensity of the ray is
changed. This ever changing beam
after having passed through the film.
IS again focused through another lens
outside the cylinder onto the sensitive
element of phOtO-electric cell. a re-
cent development which transforms the
light waves into electrical impulses or
waves. which can be transmitted by
radio much the same as a regular dash
and dot message.
This photo-electric cell Is commonly
spoken of In the laboratory as the
'eye" of the transmitter. The cleo
trical resistance of this cell changes
in accordance with the amount Of light
which falls upon it, and in this way
takes care of the shading of the picture
in transmission.
The Photo-Eiectric Cell.
nj fr1n c
practically without any lost motion.
That is, the instant the slightest change
In the amount Of light reaches
the cell, corresponding change
in the output current of the cell takes
place. In this way the eye" of the
transmitter is able to "see" even the
tiniest light variations. In fact the
"eye" sees and records electrically mil
lions of different current impulses as
the film sweeps by the light beam from
inside the cylinder.
The photo-electric cell is, therefore,
responsible for reproducing an infinite
number of different electric current
values which correspond with the light
or dark areas of the picture being
transmitted
In order 10 cover all of the original
film, the glass cylinder is rotated back
and forth and in this way the entire
surface is eventually exposed to the
piercing light leam. The film rOtates
through an angle equal to the width of
the picture one notch at time. Thus,
line upon line, the whole picture Is
covered.
After the sigral impulses or electric
waves from the photo-electric cell pass
through series of vacuum tube am
plifiers, they are fed into mOdulating
device ready for transmission. The
electrical Interpretation of the picture
is then transmitted over land wires
from the London laboratory to the
Carnavon tWales) high-power trans
mtting station of the Marconi Wire
less Telegraph Company, Ltd. Here
the electric impulses ON the land wire
operate small relays which turn on and
off the high value currents flowing
from the 2O0-kilowatt generator to the
antenna system. This higll-power cleo
tTlCdl olltTSy iedNIHS lue ant emma III In
terrupted impulses, similar to dots and
dashes of the telegraph code. creates
the ether waves which carry the photo
graph through space 1900 miles to the
receiving station on this side of the
Atlantic. located at Riverhead, Long
Island.
No Special Circuits Needed.
The development of the ph0to-radiO-
gram transmitter has purposely been
carried on in connection with the eS-
tablished radio transmitting stations
now engaged in sending radlograms
daily between Europe and America
Thus the new device does not require
the preparation Of any special radio
circuits for efficient operation.
AT Riverhead. Long Island, in the
Radio Corporations central receiving
station the operator tunes in to the
Carnavon station. He receives the pic
ture just the same as lie would Il radio