Boy thinking with coloured light and code background

Operation Decode

Mission Four: Morse Code

Before electronic communication, messages had to be sent physically. Information travelled at the speed of the fastest runner or quickest horse. This all changed with the introduction of Morse code in 1838. Named after its inventor, Samuel Morse, Morse code allowed messages to be sent very quickly over long distances using electricity.

While not encryption in the strictest sense, Morse code can still be described as a form of substitution cipher. In this case the letters of the alphabet, along with the numbers 0 – 9 are replaced with set sequences of dots and dashes.


Morse code uses dots and dashes (sometimes called dits and dahs) to represent different letters and numbers. These can be sounds, flashes of light, or just about anything else that can be clearly turned off and on.

Regardless of what is being used to transmit the code, it is the relative length of dots and dashes that is important.

  • A dash is generally three times as long as a dot
  • Dots and dashes within the same letter are separated by a blank space that is the same length as a dot
  • Letters in the same word are separated by a blank space equal to three dots
  • Words in a message are separated by a blank space equal to seven dots

Watch the flashing lights below, and see if you can use the Morse code alphabet to work out what the message says…

Morse Code Alphabet

Activity 4:

Try and figure out the secret code shown in Morse code below by using the Morse code alphabet. Each circle that lights up represents each letter in the secret word.

Tip: Try and focus on one word at time and write it down so you don’t forget it.

Strengths and Weaknesses


  • Versatile. Morse code can be transmitted using light, sound, or even blinking your eyes
  • Can be used to send messages of any length
  • Can be learned and used easily


  • Morse code is more a language Widely known, so messages can be easily understood by anyone who knows Morse code