https://www.codewars.com/kata/decode-the-morse-code-advanced
In this kata you have to write a Morse code decoder for wired electrical telegraph.
Electric telegraph is operated on a 2-wire line with a key that, when pressed, connects the wires together, which can be detected on a remote station. The Morse code encodes every character being transmitted as a sequence of "dots" (short presses on the key) and "dashes" (long presses on the key).