Editing Q code (section)

==Later use==
Over the years the original Q-codes were modified to reflect changes in radio practice. For example, QSW / QSX originally stood for, "Shall I increase / decrease my spark frequency?", but in the 1920s [[spark-gap transmitter]]s were gradually being banned from land stations, making that meaning obsolete.<ref>{{Cite web|url=https://books.google.com/books?id=sEeaJC_y22EC&q=spark&pg=PA14-IA15|title=Contact at Sea: A History of Maritime Radio Communications|first=Peter B.|last=Schroeder|date=December 29, 1967|publisher=Ardent Media|via=Google Books}}</ref> By the 1970s, the ''Post Office Handbook for Radio Operators'' listed over a hundred Q-codes,<ref>{{cite book |title=Handbook for Radio Operators |date=1975 |publisher=Her Majesty's Stationery Office |location=London |isbn=0118804626 |pages=[https://archive.org/details/HandbookForRadioOperators/page/n172 155]–174 |url=https://archive.org/details/HandbookForRadioOperators |access-date=16 April 2019}}</ref> covering a wide range of subjects including radio procedures, meteorology, radio direction finding, and search and rescue.

Some Q-codes are also used in [[aviation]], in particular QNE, QNH and QFE, referring to certain [[altimeter setting]]s. These codes are used in radiotelephone conversations with [[air traffic control]] as unambiguous shorthand, where safety and efficiency are of vital importance. A subset of Q-codes is used by the [[Miami-Dade County, Florida]] local government for law enforcement and fire rescue communications, one of the few instances where Q-codes are used in ground voice communication.<ref>{{cite magazine |magazine=National Communications Magazine |url=http://bearcat1.com/radiofl.htm |title=Radio codes & signals – Florida |access-date=2010-01-30}}</ref>

The QAA–QNZ code range includes phrases applicable primarily to the aeronautical service,<ref>{{cite web |url=http://www.airwaysmuseum.com/Q%20code.htm |title=The Q-Code |access-date=5 September 2016}}</ref> as defined by the [[International Civil Aviation Organization]].<ref>{{cite book |publisher=[[ICAO]] |series=Procedures for Air Navigation Services (PANS) |id=Doc 8400 |title=The ICAO Q-Code}}</ref> The QOA–QQZ code range is reserved for the maritime service.  The QRA–QUZ code range includes phrases applicable to all services and is allocated to the [[International Telecommunication Union]].<ref>{{cite web |url=http://www.globalsecurity.org/military/library/policy/navy/nrtc/14244_ch4.pdf |title=SM |access-date=2016-09-06}}</ref> QVA–QZZ are not allocated.<ref>{{cite web |url=http://www.portland-amateur-radio-club.org.uk/resources/q-codes.pdf |title=portland-amateur-radio-club.org.uk |access-date=5 September 2016 |url-status=dead |archive-url=https://web.archive.org/web/20111006210352/http://www.portland-amateur-radio-club.org.uk/resources/q-codes.pdf |archive-date=6 October 2011}}</ref> Many codes have no immediate applicability outside one individual service, such as maritime operation (many QO or QU series codes) or [[radioteletype]] operation (the QJ series).<ref>{{cite web |url=http://kyalami.homeip.net/qcodes.htm |title=Q-Codes |access-date=2009-03-20 |archive-url=https://web.archive.org/web/20090323113250/http://kyalami.homeip.net/qcodes.htm |archive-date=2009-03-23 |url-status=dead }}</ref>

Many military and other organisations that use Morse code have adopted additional codes, including the [[Z code]] used by most European and [[NATO]] countries. The Z code adds commands and questions adapted for military radio transmissions, for example, "ZBW 2", which means "change to backup frequency number 2", and "ZNB abc", which means "my checksum is abc, what is yours?"<ref>{{cite web |url=http://www.armymars.net/ArmyMARS/DigitalOps/Resources/acp131-operating-sigs.pdf |id=ACP 131(E) |archive-url=https://web.archive.org/web/20111119091213/http://www.armymars.net/ArmyMARS/DigitalOps/Resources/acp131-operating-sigs.pdf |archive-date=2011-11-19 |series=Communications Instructions |title=Operating Signals |date=March 1997 |url-status=usurped |quote=Chapter&nbsp;2 contains a full list of 'Q' codes}}</ref>

Used in their formal question / answer sense, the meaning of a Q-code varies depending on whether the individual Q-code is sent as a question or an answer. For example, the message "QRP?" means "Shall I decrease transmitter power?", and a reply of "QRP" means "Yes, decrease your transmitter power", whereas an unprompted statement "QRP" means "Please decrease your transmitter power". This structured use of Q-codes is fairly rare and now mainly limited to amateur radio and military [[Morse code]] (CW) traffic networks.

Under U.S. F.C.C. Regulations, CFR 47 97.113(a)(4), Amateurs are not permitted to 'transmit codes or ciphers' (historical description), allowing only that 'plain- language communications' may be transmitted. The term 'Q-Signal' has been historically used in that context, not 'Q-Code,' - the use of 'Code' is technically a violation of F.C.C. Regulations. This essentially examples, in the U.S. the historic separation between Amateur and Commercial/Military radio services