You may like to read the article on Morse code before attempting this question. Morse's letter analysis was done over 150 years ago, so might there be a better allocation of symbols today?
This article for teachers looks at some suggestions taken from the
NRICH website that offer a broad view of data and ask some more
probing questions about it.
Written for teachers, this article discusses mathematical
representations and takes, in the second part of the article,
examples of reception children's own representations.