There was the identical apparatus with its marvelously sensitive
receiver, which, while installed in Scotland, had correctly registered
signals from an amateur radio station in America.
A little later they stood entranced in the Convention Hall before a
new, beautifully modeled radio amplifier, so massive that the volume
of music it poured forth actually seemed to cause vibration in the
walls of the great room in which they stood.
One of the most interesting features was the radio-controlled
automobile. The crowd before this almost incredible invention was
so dense that the operator was handicapped in his demonstration.
The car was about seven feet in length, with a cylindrical mass of
wire rising about six feet above its body. It was upon this that the
swiftly moving car caught signals from antennae stretched across the
hall. The boys watched, fascinated, as the inventor, opening and
closing the switches in its mechanism by use of a radio wave of one
hundred and thirty-five metres in length, caused the small car to
back out of its garage and run about the hall without a driver,
delivering papers and messages, afterward returning to the garage.
Then they saw the transmitters that could shoot radio messages into
space, and hung entranced over the moving pictures of what happens
in a vacuum tube.
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