Editing SOS (section)

===World War II suffix codes===
During [[World War II]], additional codes were employed to include immediate details about attacks by enemy vessels, especially in the [[Battle of the Atlantic]]. The signal "SSS" signaled attacked by submarines, while "RRR" warned of an attack by a surface raider, "QQQ" warned of an unknown raider (usually an [[Armed merchantman#Auxiliary cruisers|auxiliary cruiser]]), and "AAA" indicated an attack by aircraft. They were usually sent in conjunction with the SOS distress signal. All of these codes later switched from three repeats of the letter to four repeats, e.g., "RRRR".

None of these signals was used on its own. Sending SOS as well as the urgency signal ("XXX" in [[continuous wave|CW]], and "PAN-PAN" in voice)<ref>[https://babel.hathitrust.org/cgi/pt?id=mdp.39015021093961&view=1up&seq=173 "1421. Urgent Marine Information Broadcast Format"], ''United States Coast Guard Communication Manual'' (CG-233), 1959 edition, page 14-3.</ref> and safety signal ("TTT" in CW, and "SECURITE" in voice)<ref>[https://babel.hathitrust.org/cgi/pt?id=mdp.39015021093961&view=1up&seq=174 "1422. Safety Marine Information Broadcast Format"], ''United States Coast Guard Communication Manual'' (CG-233), 1959 edition, page 14-4.</ref> used similar procedures for effectiveness.