While not frequently used in today’s world, I believe Morse code is a nice “old” skill to know for survival purpose or to be employed as an assistive technology. Please read about it below.
Excerpt from Wikipedia:
‘Morse code’ is a type of character encoding that transmits telegraphic information using rhythm. Morse code uses a standardized sequences of short and long elements to represent the letters, numerals, punctuation and special characters of a given message. The short and long elements can be formed by sounds, marks, or pulses, in on off keying and are commonly known as “dots” and “dashes” or “dits” and “dahs”. The speed of telecommunication transmission is often measured in baud. However, in the case of Morse code, it is measured as WPM speed.
Excerpt from Scouting Resources:
In Morse code, timing is important to ensure that a coherent message is received. The actual length of a dot can be as long as you like, but obviously it should be short enough that messages can be sent quickly and long enough to be heard over great distances. Once this standard unit of time has been established, a dash should last three times as long as a dot. The pause between individual dots and dashes should take as long as a single dot, the pause between two characters should take as long as a dash and the pause between two words should be twice as long as a dash (six times as long as a dot).