evision: - Early Television Foundation

1 6 TELEVISION: THE REVOLUTION
America. Actually, the mathematics of what
goes on inside the iconoscope is enough to send
Dr. Einstein away for a rest-cure. But for all
practical purposes, this simple description covers
quite accurately the events which take place
inside the sealed glass tube of the tele-camera.
Miss Grable and the cathode
Now, back to
beam. After the "electronic milk-man" has completed
one sweep across the mosaic, it zigzags
back to the other edge and begins another sweep,
slightly lower than before. This zigzagging by
the cathode beam is called "scanning." At each
tiny electric eye along the way,
the cathode
beam says, in effect, "How much electricity do
you need?" And the electric eye, depending
upon how big a spurt of electricity Miss Grable's
picture has caused it to give out,
tells the
cathode beam how much current it needs to
come back to normal. And so the electronic
milk-man scans the whole mosaic giving a
charge of electricity to each electric eye in proportion
to the brightness of the light which fell
on that particular part of the mosaic. All in all,
the cathode beam makes five-hundred-andtwenty-five
zigzag sweeps across the mosaic
each line being slightly lower than the one be-