The Morse code for "A"
The Letter "A" with the 'Dit" and "Dah" placed on the letter as a memory aid.
In the event of a serious crisis, communication will be a challenge to say the least.
You will likely have to deal with power outages, inoperable cell phones, and the need to communicate covertly. In this kind of circumstance Morse code is a godsend. It requires little to no power or technology and very few people are able to interpret Morse code communication. In this day and age Morse Code is a lost skill, yet fortunately it is very easy to learn!
The above based mnemonic Braden-Powell included in the Girl Guides handbook in 1918
https://en.wikipedia.org/wiki/Morse_code_mnemonics
Infographic source: http://survivalized.com/morse-code-alphabet/