Movies for TV - Early Television Foundation

170
FUNDAMENTALS
The functioning of the circuit is extraordinarily ingenious and
provided that a number of serious physical difficulties can be over-
So far re-
come it may offer a practical solution to the problem.
sults have been rather unsatisfactory compared with colored mo-
tion pictures.
Time multiplex transmission is used with a band-width of four
MC for full modulation. The color camera at the transmitting
end produces three signals, green, red, and blue. These signals
are sampled electronically in rapid sequence, combined, and
broadcast as a single signal.
At the receiver, separation is performed, so that the signal
representing each color goes to an electron tube which produces a
picture in that particular color. The green, red, and blue signals
are applied to their individual kinescopes. The three colors are
then projected simultaneously and produce the complete picture.
One of the fundamental characteristics of the system is the
application of time multiplex transmission, which has been
adopted and applied to television from radio telegraphy. Other
innovations are the electronic sampler and picture dot interlacing.
The electronic sampler has to function with microsecond pre-
cision in sampling the colors. From the sampler the signals, representing
the three primary colors, are fed to an electronic combin-
ing device. Standard synchronizing signals from the synchronizing
generator are also applied at this point, and the principle of mixed
high frequencies
is also utilized.
Each color is sampled 3,800,000 times a second for the three
colors a total of 1 1 ,400,000 samples a second. The green signal is
sampled
and less than nine hundred-millionths of a second later
the red is sampled, and then the blue. This means that the signals
of each color are transmitted at an approximate rate of one every
four-millionth of a second. When viewed on the screen of a re-
ceiver, the recurrence of the signal is so rapid that the color appears
to be constant.
The three color signals from the camera are combined in an
electronic adder and then passed through a band-pass filter. The
output of this filter contains frequencies between two and four