For the light source for radio photographs a filament lamp is employed,
and in a single turn coil enclosed in a hydrogen atmosphere. This
miniature filament coil is imaged on a photo negative plate, and the
variation in the light is caused by putting the incoming radio signals
through this lamp, perhaps after the filament has been brought to a red
glow by a battery current. By adjusting the speed of the motor to the
temperature change of this filament soft gradations of light and shade
are obtained which probably can never be equaled by any other device, a
photograph of true photographic value, entirely free of lines.
The author wishes to take this occasion to express his appreciation of
the splendid assistance of the General Electric Company, under the
personal supervision and hearty cooperation of Mr. L. C. Porter, who
from the very first has shown his confidence in the ultimate successful
conclusion of this development.