On a recumbent bike forum that I frequent, the owner made reference to a Laser Spy System that was said to be invented in the Soviet Union by Leon Theremin in the late 1940s. The reference was to an article with instructions on making your own laser listening device. Point this laser toward a window and the laser will pick up the vibrations and transfer that into sound.
The first reaction I had to that was “I think I got one of those in a box of cereal when I was a kid”. That was right after I got my diving submarine with one box top and 50 cents sent to the Kellogg Company, Battle Creek, Michigan. Yeah, you spelled it all out. There were no 2 letter state abbreviations and oh, there was no zip codes in those days. After scanning the DIY laser article I wondered if I would still be able to find any information on my diving submarine powered by baking powder. Yep, sure nuff, a ton of em. First one I looked at was a vid on how to make one from a carrot and toothpicks. Good science fair project. This was followed by a whole slue of links from Amazon dot com and others selling replicas of the toy from the 50’s. http://www.torgo.org/bpsubs/index.shtml has instructions on how they work and where to buy them.
As I remember, the sub I got from Kellogg was only a couple of inches long, I see the ones they are selling now are 5 inches or larger. Then again, maybe I just don’t remember right.
Those were the good ole days.