The young man in this drawing is now a senior citizen, but in 1965, he was taking part in the school science fair, using a project shown in the Winter 1965 issue of Elementary Electronics. He was communicating with a light beam, with a rudimentary setup consisting of two audio amplifiers. The output of one of them was hooked directly to a light bulb (in series with a 3 volt battery), and the input of the other one was hooked to a photocell.
According to the article, this unit was good for demonstration purposes only, and was only capable of a couple of feet. I’m surprised that they are so conservative in their estimate, since I made virtually the same setup when I was a kid, and it traversed the length of the house without much difficulty.
The only difference in my version was the addition of a transformer to the output of the first amplifier. The primary was hooked to the amp, and the secondary was wired in series with the battery. I used a flashlight, and just sandwiched two pieces of foil, insulated by cardboard, between the lamp and the battery terminal. I suspect my use of a flashlight, complete with its parabolic reflector, was probably an important factor in my success.
