The
Q code is a standardized collection of three-letter message encodings, also known as a
brevity code, all of which start with the letter "Q", initially developed for commercial
radiotelegraph communication, and later adopted by other radio services, especially
amateur radio. Although Q codes were created when radio used
Morse code exclusively, they continued to be employed after the introduction of voice transmissions. To avoid confusion, transmitter
call signs are restricted; while an embedded three-letter Q sequence may occur (for instance when requested by an amateur radio station dedicated to
low-power operation), no country is ever issued an
ITU prefix starting with "Q". The codes in the range QAA–QNZ are reserved for aeronautical use; QOA–QQZ for maritime use and QRA–QUZ for all services.