Peter Wright's book, "Spycatcher" from about 1987 described an early version of
this, at least in the context of a teletype printing.
         Jim Bell

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Can hackers tell what you’re texting or searching just by listening?: [1]https:/
/nypost.com/2019/06/05/can-hackers-tell-what-youre-texting-or-searching-just-by-
listening/

References

   1. https://nypost.com/2019/06/05/can-hackers-tell-what-youre-texting-or-searching-just-by-listening/