Morse code is a type of character encoding that transmits telegraphic information using rhythm. Morse code uses a standardized sequence of short and long elements to represent the letters, numerals, punctuation and special characters of a given message. When captured by the Travelers, Lt. Colonel John Sheppard modified a damaged Subspace communication array to send a SOS message through subspace using morse code. (SGA: "Travelers")
Lt. Matthew Scott with the help of Eli Wallace used the Stargate on Novus colony to send a message in Morse code to Destiny. (SGU: "Common Descent")