Editing Morse code (section)

== International Morse code ==
Morse codes of one version or another have been in use for more than 160&nbsp;years — longer than any other [[electrical]] message encoding system. What is called Morse code today is actually somewhat different from what was originally developed by Vail and Morse. The Modern International Morse code, or ''continental code'', was created by [[Friedrich Clemens Gerke]] in 1848 and initially used for telegraphy between [[Hamburg]] and [[Cuxhaven]] in Germany. Gerke changed nearly half of the alphabet and all of the [[Numerical digit|numerals]], providing the foundation for the modern form of the code. After some minor changes to the letters and a complete revision of the numerals, International Morse Code was standardized by the International Telegraphy Congress in 1865 in Paris, and later became the standard adopted by the [[International Telecommunication Union]] (ITU). Morse and Vail's final code specification, however, was only really used for land-line telegraphy in the United States and Canada, with the International code used everywhere else, including all ships at sea and sailing in North American waters. Morse's version became known as ''[[American Morse code]]'' or ''railroad code'', and is now almost never used, with the possible exception of historical re-enactments.

===Aviation===
[[File:VFR Chart Cayo Largo Del Sur VOR-DME.png|thumb|Cayo Largo Del Sur VOR-DME]]
In [[aviation]], pilots use [[radio navigation]] aids. To allow pilots to ensure that the stations they intend to use are serviceable, the stations transmit a set of identification letters (usually a two-to-five-letter version of the station name) in Morse code. Station identification letters are shown on air navigation charts. For example, the [[VHF omnidirectional range|VOR-DME]] based at [[Vilo Acuña Airport]] in [[Cayo Largo del Sur|Cayo Largo del Sur, Cuba]] is identified by "[[call sign|UCL]]", and Morse code '''{{sc|UCL}}''' is repeatedly transmitted on its radio frequency.

In some countries, during periods of maintenance, the facility may instead transmit the signal {{nobr|'''{{sc|TEST}}'''}} ({{nobr|{{Morse|dash}} {{Morse|dot}}{{Morse|dot|dot|dot}}{{Morse|dash}}}}), or the [[call sign|identification]] may be removed, which tells [[Aviator|pilots]] and [[navigator]]s that the station is unreliable. In Canada, the identification is removed entirely to signify the navigation aid is not to be used.<ref name=FAA-2015-Air-Nav/><ref name=Canada-AIM-2003-COM-3-2/>

In the aviation service, Morse is typically sent at a very slow speed of about 5&nbsp;words per minute. In the U.S., pilots do not actually have to know Morse to identify the transmitter because the dot/dash sequence is written out next to the transmitter's symbol on aeronautical charts. Some modern navigation receivers automatically translate the code into displayed letters.[[File:NonDirectional Beacon WG.ogg|thumb|right|The sound of non-directional beacon '''{{sc|WG}}''', on 248&nbsp;kHz, located at 49.8992&nbsp;North, 97.349197&nbsp;West,<ref name=Pilotnav-sps-10404/> near [[Winnipeg James Armstrong Richardson International Airport|Winnipeg's main airport]]]]

===Amateur radio===
[[File:VibroplexBug.jpg|thumb|right|[[Vibroplex]] brand semiautomatic key{{efn|name=bug_op_note}} (informally called a "bug" since it vaguely resembles a [[stick insect]]). ]]
International Morse code today is most popular among [[amateur radio]] operators, in the mode commonly referred to as "[[continuous wave]]" or "CW".{{efn|
The name ''[[continuous wave]]'' was chosen to distinguish the single-frequency [[List of amateur radio modes|transmission mode]] from the sliding-frequency [[damped wave (radio transmission)|damped wave signals]] from now-banned [[spark-gap transmitter]]s. Although the modern {{sc|on}} / {{sc|off}} signal itself is interrupted, not continuous, it does (ideally) maintain a single, constant frequency [[carrier wave]] throughout any one transmission.
}}
Other, faster keying methods are available in radio telegraphy, such as [[frequency-shift keying]] (FSK).

The original amateur radio operators used Morse code exclusively since voice-capable radio transmitters did not become commonly available until around 1920. Until 2003, the [[International Telecommunication Union]] mandated Morse code proficiency as part of the amateur radio licensing procedure worldwide. However, the [[World Radiocommunication Conference]] of 2003 made the Morse code requirement for amateur radio licensing optional.<ref name=IARU-2003-07-03/> Many countries subsequently removed the Morse requirement from their license requirements.<ref name=ARRL-Letter-2005-08-12/>
[[File:2022-11-06 0204 40 Meter CW.ogg|thumb|Morse code recorded on the [[40-meter band|40&nbsp;meter ham radio band]] (31&nbsp;sec).]]
Until 1991, a demonstration of the ability to send and receive Morse code at a minimum of five words per minute ({{sc|wpm}}) was required to receive an amateur radio license for use in the United States from the [[Federal Communications Commission]]. Demonstration of this ability was still required for the privilege to use the [[shortwave|shortwave bands]]. Until 2000, proficiency at the 20&nbsp;{{sc|wpm}} level was required to receive the highest level of amateur license (Amateur Extra Class); effective April 15, 2000, in the FCC reduced the Extra Class requirement to 5&nbsp;{{sc|wpm}}.<ref name=ARRL-2000-Part-97-amended/> Finally, effective on February 23, 2007, the FCC eliminated the Morse code proficiency requirements from all amateur radio licenses.

While voice and data transmissions are limited to specific amateur radio bands under U.S. rules, Morse code is permitted on all amateur bands: [[2200-meter band|LF]], [[630-meter band|MF low]], [[160-meter band|MF high]], [[High frequency|HF]], [[VHF]], and [[UHF]]. In some countries, certain portions of the amateur radio bands are reserved for transmission of Morse code signals only.

Because Morse code transmissions employ an [[on-off keying|on-off keyed]] radio signal, it requires less complex equipment than other [[List of amateur radio modes|radio transmission modes]]. Morse code also uses less [[signal bandwidth|bandwidth]] (typically only 100–150&nbsp;[[hertz|Hz]] wide, although only for a slow data rate) than voice communication (roughly 2,400~2,800&nbsp;Hz used by [[single-sideband modulation|SSB voice]]).

Morse code is usually received as a high-pitched audio tone, so transmissions are easier to copy than voice through the noise on congested frequencies, and it can be used in very high noise / low signal environments. The fact that the transmitted power is concentrated into a very limited bandwidth makes it possible to use narrow receiver filters, which suppress or eliminate interference on nearby frequencies. The narrow signal bandwidth also takes advantage of the natural aural selectivity of the human brain, further enhancing weak signal readability.{{citation needed|date=December 2020}} This efficiency makes CW extremely useful for [[DXing|DX (long distance) transmissions]], as well as for low-power transmissions (commonly called "[[QRP operation]]", from the [[Q-code]] for "reduce power"). There are several amateur clubs that require solid high speed copy, the highest of these has a standard of 60&nbsp;{{sc|WPM}}. The [[American Radio Relay League]] offers a code proficiency certification program that starts at 10&nbsp;{{sc|wpm}}.

The relatively limited speed at which Morse code can be sent led to the development of an extensive number of abbreviations to speed communication. These include prosigns, [[Q code]]s, and a set of [[Morse code abbreviations]] for typical message components. For example, '''{{sc|CQ}}''' is broadcast to be interpreted as "seek you" (I'd like to converse with anyone who can hear my signal). The abbreviations '''{{sc|OM}}''' (old man), '''{{sc|YL}}''' (young lady), and '''{{sc|XYL}}''' ("ex-young lady" – wife) are common. '''{{sc|YL}}''' or '''{{sc|OM}}''' is used by an operator when referring to the other operator (regardless of their actual age), and '''{{sc|XYL}}''' or '''{{sc|OM}}''' (rather than the expected '''{{sc|XYM}}''') is used by an operator when referring to his or her spouse. '''{{sc|QTH}}''' is "transmitting location" (spoken "my Q.T.H." is "my location"). The use of abbreviations for common terms permits conversation even when the operators speak different languages.

Although the traditional [[telegraph key]] (straight key) is still used by some amateurs, the use of mechanical semi-automatic [[keyer]]s{{efn|
name=bug_op_note|
The semiautomatic key paddle, when pressed to the right by the thumb, kicks a clockwork-like horizontal pendulum that generates a series of ''dits'', the length and timing of which are controlled by a sliding the pendulum weight toward the rear of the unit. When pressed to the left by the knuckle of the index finger, the paddle generates a single ''dah'', the length of which is controlled by the operator. Multiple ''dahs'' require multiple presses. Left-handed operators may use a key built as a mirror image of this one.
}}
(informally called "bugs"), and of fully automatic electronic [[keyer]]s (called "single paddle" and either "double-paddle" or "iambic" keys) is prevalent today. [[Software]] is also frequently employed to produce and decode Morse code radio signals. The [[ARRL]] has a readability standard for robot encoders called ''ARRL Farnsworth spacing''<ref name=ARRL-x9004008-Farnsw/> that is supposed to have higher readability for both robot and human decoders. Some programs like WinMorse<ref name=Winmorse-custom-Farnsw/> have implemented the standard.

===Other uses===
Radio navigation aids such as [[VHF omnidirectional range|VOR]]s and [[Non-directional beacon|NDB]]s for aeronautical use broadcast identifying information in the form of Morse Code, though many [[VHF omnidirectional range|VOR]] stations now also provide voice identification.<ref name=FCC-AIM-ch-1/> Warships, including those of the [[U.S. Navy]], have long used [[signal lamp]]s to exchange messages in Morse code. Modern use continues, in part, as a way to communicate while maintaining [[radio silence]].

[[Automatic Transmitter Identification System (television)|Automatic Transmitter Identification System]] (ATIS) uses Morse code to identify uplink sources of analog satellite transmissions.
{{clear}}

Many [[amateur radio repeater]]s identify with Morse, even though they are used for voice communications.

===Applications for the general public===
[[File:SOS.svg|thumb|left|250px|Representation of Morse code '''{{overline|SOS}}''']]
An important application is signalling for help through [[SOS]], "{{morse|dot|dot|dot|dash|dash|dash|dot|dot|dot}}". This can be sent many ways: keying a radio on and off, flashing a mirror, toggling a flashlight, and similar methods. The [[SOS]] signal is not sent as three separate characters; rather, it is a [[prosigns for Morse code|prosign]] {{sc|'''{{overline|SOS}}'''}}, and is keyed without gaps between characters.<ref name=QSL-Prosigns/>

===Morse code as an assistive technology===
Morse code has been employed as an [[assistive technology]], helping people with a variety of [[disability|disabilities]] to communicate.<ref>{{cite book |first=Thomas W. |last=King |title=Modern Morse code in rehabilitation and education: New applications in assistive technology |publisher=Allyn & Bacon |date=2000 |isbn=9780205287512 |oclc=41070880 |url=https://archive.org/details/modernmorsecodei0000king/page/n8/mode/2up}}</ref><ref>{{cite web |first=Jim |last=Lubin |title=Morse Codes for Computer Access |date=2020 |publisher= |url=https://www.makoa.org/jlubin/morsecode.htm}}</ref>{{efn|
For people with severe disabilities, both one- and two-switch Morse can be difficult because both depend, to some extent, on timing. ... access products can also offer "three-switch Morse.". In three-switch Morse code, one switch signals dit, while another signals dah, just like two-switch Morse. But a third switch is used to indicate that the letter is complete. This removes the necessity of timing to send Morse code. – D.K. Anson (2018)<ref name=Anson-2018/>
}}<ref>{{cite web |title=Morse Code |date=2020 |publisher=Ace Centre (UK ACC Charity) |url=https://acecentre.org.uk/projects/morse-code}}</ref> For example, the Android operating system versions&nbsp;5.0 and higher allow users to input text using Morse Code as an alternative to a keypad or [[handwriting recognition]].<ref name=Google-android-9011881/>

Morse can be sent by persons with severe motion disabilities, as long as they have some minimal motor control. An original solution to the problem that caretakers have to learn to decode has been an electronic typewriter with the codes written on the keys. Codes were sung by users; see the voice typewriter employing Morse or votem.<ref name=Newell-Nabarro-1968/>

Morse code can also be translated by computer and used in a speaking communication aid. In some cases, this means alternately blowing into and sucking on a plastic tube ("[[sip-and-puff]]" interface). An important advantage of Morse code over [[Switch access scanning|row column scanning]] is that once learned, it does not require looking at a display. Also, it appears faster than scanning.

In one case reported in the radio amateur magazine ''[[QST]]'',<ref name=Ross-1992-03/> an old shipboard radio operator who had a [[stroke]] and lost the ability to speak or write could communicate with his physician (a radio amateur) by blinking his eyes in Morse. Two examples of communication in intensive care units were also published in ''[[QST magazine]]''.<ref name=Curt-1990-07/><ref name=Burch-1990-07/> Another example occurred in 1966 when [[prisoner of war]] [[Jeremiah Denton]], brought on television by his [[North Vietnam]]ese captors, Morse-blinked the word '''{{sc|TORTURE}}'''. In these two cases, interpreters were available to understand those series of eye-blinks.