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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