[wonderous]

Anyone that finds this interest should look at how “The Thing” (1945) worked: https://en.wikipedia.org/wiki/The_Thing_(listening_device)

EDIT: Here are some diagrams of how it works:

https://hackaday.com/2015/12/08/theremins-bug/

[malikNF]

You should submit this as a HN link, really interesting story. Thanks.

[Tempest1981]

2 months ago: https://news.ycombinator.com/item?id=15498685

11 previous submissions: https://hn.algolia.com/?query=listening%20thing&sort=byPopul...

5 more: https://hn.algolia.com/?query=theremin%20soviet

[mxuribe]

I had heard of this, but didn't know its name, so never looked it up! Thanks for this link; very cool!