Q code

The Q-code is a standardized collection of three-letter codes that each start with the letter "Q". It is an operating signal initially developed for commercial radiotelegraph communication and later adopted by other radio services, especially amateur radio. To distinguish the use of a Q-code transmitted as a question from the same Q-code transmitted as a statement, it is suffixed with the standard Morse question mark UD (dit dit dah dah dit dit).

Although Q-codes were created when radio used Morse code exclusively, they continue to be employed after the introduction of voice transmissions and are commonly used on CW (Morse code), digital, and, to a lesser extent, phone modes in amateur radio. To avoid confusion, regulations are in place that prevent call signs containing Q codes from being issued.