Evening star. [volume] (Washington, D.C.) 1854-1972, 1930-04-27
TELEWS|ON STAGE
IS EXPERIMENTAL
Science Is. Bending Every e.
fort to Hasten Day of
Success.
BY the Associated Press.

NEW YORK.-Television that in
triguing subject, is making another try
for recognition as an adjunct to broad
casting.
When it will succeed cannot be FORE
cast, but scientists are bending every
effort to hasten the day. Demonstra-
tons designed to show Just where tels-
vision stands indicate that considerable
progress has ben made In the develop
ment of the more complicated appa-
ratus as well as In the simple equip
ment.
However, present television Is largely
of the experimental type. It might be
compared to the crystal detector stage
of radio or the movies when "one min
ute to change reels" was Important.
Radio fans, vitality interested in the
day when they will be able to see and
hear entertainers, probably will have to
be satisfied for some time to come with
simple apparatus and with views Of
heads only. Then, too, pair of sets
will be necessary to receive synchro-
niZed programs One Will be Tor SOUND
and the other for vision.
Television might be considered as the
transmission of light rays. Actually,
what is sent is a string of signals,
representing lights and shadows, which,
when put together in their proper Sc
ouence, give the impression Of a NOV
ing picture.
Vacuum Tubes Have Big Role.
Vacuum tubes play an important part.
The television transmitting tube Is the
photoelectric cell, sensitive to light.
which makes an electric photograph OF
the object being televised. The receiv-
ing tube, or neon lamp, changes these
electrical impulses back into light, func-
tioning similarly to the loud speaker
for sound.
Some means of interrupting the light
rays is necessary. This is the purpose
of the scanning disk. 1t is circular
plate containing tiny holes, equally
placed in the form of spiral. Each
hole admits a ray of light, its density
determining the type Of impulse.
In most televiSion systems, scanning
disks are used both at the transmitter
and the receiver. The one at the re-
ceiver must be kept in step with that
at the transmitter. The disk is oper-
ated at high speed, in front OF the
photoelectric cell or the neon lamp. In
the receiver the locker is actually gaz-
ing at a small plate In the neon lamp.
Radio Transmitter Required.
Lenses are used in transmission to
intensity the light cast upon the object
and reflected to the photoelectric cell;
and in reception to amplify the picture,
which, before being enlarged, is only an
inch or two square.
In addition to the television trans
uaitter, a radio tranSmitter also is re-
CURED at the sending end, while at the
receiver, a radio set with special ampi-
fer must be used in addition to the
teleRision reproducer.
In the Bell laboratory's demonstration
Of two-way television part Of the sue
cess was attributed to the use Of .
72-hole scanning disk which gives
greater detail This disk makes ID
revolutions per second, creating ID
photographs in that period and produc-
ing a moving picture. With each revo-
luton 70 electrical impulses are set up,
or 1895 per second.
Five telephone circuits were the con-
Meeting links between the two television
booths used in the test, although eng1-
neers explained that radio could have
been employed. Behind each oootn
were concealed a receiver and trans
mitter, each having its own scanning
disk and driving motor. Twelve photo
electric cells, sensitive to q blue light,
were hidden in the sides of the booths.
The neon lamp in this case was q new
type, being water cooled and with a
viewing" plate approximately 2 inches
square. The blue light was used as the
scanning beam, which bathes the face
of the sitter and is reflected to the cells.
Demonstration Experimental.
The frequency band for each tele-
vision circuit was AZ, 900 cycles, equal to
the space required by four broadcast
stations. Besides two circuits for tele-
vision, two others were used for the
voice, and q fifth carried 1257-cycle
signal to keep the scanning disks in
synchroniZation.
The demonstration, together with the
elaborate equipment, while giving an in
sight into what the future may hold
for telephone communication, must be
considered from no standpoint other
than experimental.