Popular Electronics Magazine, June 1955
The cover of June, 1955, Popular Electronics depicts an
attractive young woman speaking over her "Beam of Light" transmitter.
Talking With Light Beams was the title of the cover article,
which contained construction plans for this device
The transmitter portion of this device was simplicity itself. You
simply wired a telephone carbon microphone in series with a 12-volt
battery powering an ordinary portable spotlight.
The receiver used a type 930 phototube and two other low-voltage
tubes (types 1S5 and 1S4). A concave shaving mirror was used to
concentrate the light for the phototube, allowing reception at
greater distances.
The Beam of Light
transmitter was not terribly practical. If you used it
in broad daylight, as the cover painting shows, it's doubtful whether
anything could be received at all. (The bright ambient sunlight would
drown out the weaker beams from a portable spotlight.)
Moreover, unlike radio waves, light waves
are limited to line-of-sight transmission. Like the child's "telephone"
made of string and two tin cans, the light-beam transmitter could
only talk to someone who was already in plain view!
The article tries to suggest a couple of plausible applications, such as using
a light-beam transmitter to talk to a next-door neighbor, thus freeing
up your regular phone line. Another idea was to use it as a "baby monitor,"
transmitting the sounds of children to a neighbor. I doubt that many people ever put this
device to practical use, however.
Articles such as this were really aimed
at experimenters, who built things for fun
and to learn about emerging technologies. And they illustrated techniques
that could be applied in more sensible ways. Phototubes, for instance, were
eventually used in automatic door openers and slave photoflashes.
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