Our Vietnam POWs devised a way to communicate with tapping on the floor. I guess they used rocks or something. While writing this, I decided to look it up. HERE (videos don't work)
This was the first time I have seen the method they used.
Surprising to me, is the knowledge that while tinkering here at my desk last year, I came up with something similar on my own. I wanted to be able to encode dates. I used a grid myself.
QIY is today's date. Y/M/D I find these sorts of things fascinating.
Take care.
Coded language is a bit above my “pay grade” although I did enjoy the story of the enigma codes on a history channel once. The Navajo wind talkers rings a bell too.
Besides languages, I also find regional American accents to be interesting.
Keep those awesome elegant First Lady pics coming!