The works like model uses an Arduino Nano with a buzzer and 5 LED lights. Inside the code, each letter of the alphabet is numbered and then mapped to its Morse Code sequence. Once the telegram is pressed, the button hidden inside triggers the Arduino. A 4-letter code is randomly generated and immediately begins sounding and flashing.
While there is a clear pause between letters, there is no clear distinction between the start and end of the 4-letter code. This is to give added difficulty as players may have found an order for the 4-letter code but may not know which letter is the beginning of the code.
To have the looks like model trigger the alarm, a button is hidden underneath a small cylinder by the hinge so when the telegram is pressed, a wooden dowel push down and presses the button.
Here is a video of the model in action. If you listen/watch closely, you'll be able to make out
J [.---] O [---] S [...] H [....]