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[[File:International Morse Code.svg|thumb|upright=1.2|Chart of the Morse code 26 letters and 10 numerals<ref name=ITU-R-M-1677/>]]
{{anchor|MorseKey}}
'''Morse code''' is a [[telecommunications]] method which [[Character encoding|encodes]] [[Written language|text]] characters as standardized sequences of two different signal durations, called ''dots'' and ''dashes'', or ''dits'' and ''dahs''.<ref name=Beechey-1876/><ref name=Camm-1941/> Morse code is named after [[Samuel Morse]], one of several developers of the code system. Morse's preliminary proposal for
'''International Morse code''' encodes the 26 [[ISO basic Latin alphabet|basic Latin letters]] '''{{sc|A}}''' to '''{{sc|Z}}''', one [[diacritic|accented]] Latin letter ('''{{sc|É}}'''), the [[Indo-Arabic numerals]] '''{{small|0}}''' to '''{{small|9}}''', and a small set of punctuation and messaging procedural signals ([[prosigns for Morse code|prosigns]]). There is no distinction between upper and lower case letters.<ref name=ITU-R-M-1677/> Each Morse code symbol is formed by a sequence of ''dits'' and ''dahs''. The ''dit'' duration can vary for signal clarity and operator skill, but for any one message, once the [[rhythm]] is established, a [[beat (music)|half-beat]] is the basic unit of time measurement in Morse code. The duration of a ''dah'' is three times the duration of a ''dit'' (although some telegraphers deliberately exaggerate the length of a ''dah'' for clearer signalling). Each ''dit'' or ''dah'' within an encoded character is followed by a period of signal absence, called a ''space'', equal to the ''dit'' duration. The letters of a word are [[Delimiter|separated by]] a space of duration equal to three ''dits'', and words are separated by a space equal to seven ''dits''.<ref name=ITU-R-M-1677/><ref name=TR-Paris-1949>{{cite report |title=Telegraph Regulations |orig-year=1947 |year=1949 |series=ITU History |place=Geneva, CH |publisher=[[International Telecommunication Union]] |url=https://search.itu.int/history/HistoryDigitalCollectionDocLibrary/1.36.48.en.100.pdf |page=42 |quote=the space between two words is equal to seven dots;}} — Annexed to the ''International Telecommunication Convention'', Atlantic City, 1947; revised Paris, 1949.</ref>{{efn|
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The American artist [[Samuel F. B. Morse|Samuel Morse]], the American [[physicist]] [[Joseph Henry]], and mechanical engineer [[Alfred Vail]] developed an [[electrical telegraph]] system. The simple "on or off" nature of its signals made it desirable to find a method of transmitting natural language using only electrical pulses and the silence between them. Around 1837, Morse therefore developed such a method, an early forerunner to the modern International Morse code.<ref name=Burns-2004/>{{rp|page=79}}
The Morse system for [[telegraphy]]
In his earliest design for a code, Morse had planned to transmit only numerals, and to use a codebook to look up each word according to the number which had been sent. However, the code was soon expanded by [[Alfred Vail]] in 1840 to include letters and special characters, so it could be used more generally. Vail estimated the [[letter frequency]] of English by counting the [[movable type]] he found in the [[Type case|type cases]] of a local newspaper in [[Morristown, New Jersey]].<ref name=Burns-2004/>{{rp|page=84}} The shorter marks were called "dots" and the longer ones "dashes", and the letters most commonly used were assigned the shortest sequences of dots and dashes. This code, first used in 1844, was what later became known as ''Morse landline code'', ''[[American Morse code]]'', or ''Railroad Morse'', until the end of railroad telegraphy in the U.S. in the 1970s.{{citation needed|date=May 2021}}
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# short mark, dot or ''dit'' ({{morse|dot}}): "dit duration" is one time unit long
# long mark, dash or ''dah'' ({{morse|dash}}): three time units long
# inter-element gap between the ''dits''
# short gap (between letters): one dah duration silence, three time units long
# medium gap (between words): a long silence, duration the same as two (silent) dahs sent with a normal one dit gap, seven time units
===Transmission===
Morse code can be transmitted in a number of ways: Originally as electrical pulses along a [[telegraph]] wire, but later extended to an audio tone, a radio signal with short and long tones, or high and low tones, or as a mechanical, audible, or visual signal (e.g. a flashing light) using devices like an [[Aldis lamp]] or a [[heliograph]], a common flashlight, or even a car horn. Some mine rescues have used pulling on a rope - a short pull for a dot and a long pull for a ''dah''. Ground forces send messages to aircraft with panel signalling, where a horizontal panel is a dah and a vertical panel a dit.<ref>{{cite AV media |title=NATO phonetic alphabet, codes & signals |medium=poster |date=11 January 2018 |series=Communications Services, Public Diplomacy Division |publisher=[[NATO Headquarters]] |place=Brussels, Belgium |url=https://www.nato.int/nato_static_fl2014/assets/pdf/pdf_2018_01/20180111_nato-alphabet-sign-signal.pdf
Morse messages are generally transmitted by a hand-operated device such as a [[telegraph key]], so there are variations introduced by the skill of the sender and receiver — more experienced operators can send and receive at faster speeds. In addition, individual operators differ slightly, for example, using slightly longer or shorter ''dahs'' or gaps, perhaps only for particular characters. This is called their "fist", and experienced operators can recognize specific individuals by it alone. A good operator who sends clearly and is easy to copy is said to have a "good fist". A "poor fist" is a characteristic of sloppy or hard to copy Morse code.
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Morse code is often spoken or written with ''dah'' for dashes, ''dit'' for dots located at the end of a character, and ''di'' for dots located at the beginning or internally within the character. Thus, the following Morse code sequence:
:{| style="text-align:center;"
|-▼
| '''{{sc|M}}''' || '''{{sc|O}}''' || '''{{sc|R}}''' || '''{{sc|S}}''' || '''{{sc|E}}'''▼
| {{spaces|5}} || '''{{sc|C}}''' || '''{{sc|O}}''' || '''{{sc|D }}'''|| '''{{sc|E}}'''▼
|-
| {{morse|dash|dash}} || {{morse|dash|dash|dash}} || {{morse|dot|dash|dot}} || {{morse|dot|dot|dot}} || {{morse|dot}}
| || {{morse|dash|dot|dash|dot}} || {{morse|dash|dash|dash}} || {{morse|dash|dot|dot}} || {{morse|dot}}
▲|-
▲| '''{{sc|M}}''' || '''{{sc|O}}''' || '''{{sc|R}}''' || '''{{sc|S}}''' || '''{{sc|E}}'''
▲| {{spaces|5}} || '''{{sc|C}}''' || '''{{sc|O}}''' || '''{{sc|D }}'''|| '''{{sc|E}}'''
|}
is spoken (or sung):
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| ''{{nobr|dah dah}}'' || ''{{nobr|dah dah dah}}'' || ''{{nobr|di dah dit}}'' || ''{{nobr|di di dit}}'' || ''{{nobr|dit}}''
| {{spaces|3}} || ''{{nobr|dah di dah dit}}'' || ''{{nobr|dah dah dah}}'' || ''{{nobr|dah di dit}}'' || ''{{nobr|dit}}''
|-
| {{morse|dash|dash}} || {{morse|dash|dash|dash}} || {{morse|dot|dash|dot}} || {{morse|dot|dot|dot}} || {{morse|dot}}
| || {{morse|dash|dot|dash|dot}} || {{morse|dash|dash|dash}} || {{morse|dash|dot|dot}} || {{morse|dot}}
|-
| '''{{sc|M}}''' || '''{{sc|O}}''' || '''{{sc|R}}''' || '''{{sc|S}}''' || '''{{sc|E}}'''
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|style="text-align:center;"| {{anchor|asterisk_anchor}}[*] || Codes that are ''not'' cut numbers, or are not numbers, are {{grey|'''shaded grey'''}} in the table.
|- style="vertical-align:top;"
|style="text-align:center;"| {{anchor|dagger_anchor}}[†] || There are no distinct cut-number codes for '''{{small|4}}''' or '''{{small|6}}''', since cut numbers are made by reducing multiple ''dahs'' in the standard Morse number codes to only one ''dah'', but keeping all the ''dits'' as-is; digits '''{{small|4}}''' and '''{{small|6}}''' already
|- style="vertical-align:top;"
|style="text-align:center;"| {{anchor|double_dagger_anchor}}[‡] || Some operators just send the standard code for '''{{small|5}}''', even when using other cut numbers, since five ''dits'' are still fairly short (same duration as {{nobr|cut '''{{small|3}}'''}} and {{nobr|cut '''{{small|7}}'''),}} and one might imagine a single ''dit'' possibly being misinterpreted as either a mistaken {{nobr|cut '''{{small|1}}'''}} or cut decimal point.{{citation needed|date=October 2023}}
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; Exclamation mark : There is no standard representation for the [[exclamation mark]] [''' ! '''], although the {{sc| {{overline|KW}} }} [[Digraph (orthography)|digraph]] ({{morse|dash|dot|dash|dot|dash|dash}}) was proposed in the 1980s by the [[Heathkit]] Company.{{efn|[[Heathkit]] was a popular, long-standing vendor of kits for amateur radio equipment.}} While Morse code translation software prefers the Heathkit version, on-air use is not yet universal, as some amateur radio operators in North America and the Caribbean continue to use the older {{sc| {{overline|MN}} }} digraph ({{morse|dash|dash|dash|dot}}){{efn|name=exclamation_note| {{sc| {{overline|MN}} }} or {{sc| {{overline|OE}} }}, {{morse|dash|dash|dash|dot}}, which some telegraphers unofficially use for an exclamation mark [''' ! '''], is shared with unofficial letters {{sc|Ö}}, {{sc|Ó}}, and {{sc|Ø}} used in some non-Latin alphabets.}} copied over from [[American Morse code|American Morse landline code]].
; Currency symbols : The ITU has never formally codified any [[currency symbol]]s into Morse code: The unambiguous [[ISO 4217]] currency codes are preferred for transmission (e.g. [[CNY]], [[EUR]], [[GBP]], [[JPY]], [[South Korean won|KRW]], [[USD]], etc.). However, the {{nobr|symbol [''' $ ''']}} was represented in the [[Phillips Code]]{{efn|The [[Phillips Code]] was a huge collection of abbreviations used on land line telegraphy.}} as two characters "'''{{sc|SX}}'''"; eventually operators dropped the intervening space and merged the two letter code or abbreviation into the single unofficial punctuation encoding {{sc| {{overline|SX}} }} ({{morse|dot|dot|dot|dash|dot|dot|dash}}).
; Ampersand [''' & '''] : The suggested unofficial encoding of the [[ampersand]] [''' & '''] sign listed above,{{efn|name=E_S_for_&_note}} often shown as {{sc| {{overline|AS}} }}, is also the official Morse [[Prosigns for Morse code|prosign]] for ''wait''. In addition, the [[American Morse code|American Morse encoding]] for an ampersand ({{morse|dot|aspace|dot|dot|dot}}) was similar to '''{{sc|ES}}''' ({{morse|dot}}{{morse|dot|dot|dot}}) and [[Amateur radio operators|hams]] have nearly universally carried over this use as an abbreviation for "and" (e.g. {{sc|WX HR COLD ES RAINY}} "the weather here is cold and rainy"). Since '''{{sc|ES}}''' is well established and slightly quicker than {{sc| {{overline|AS}} }}, there is no motivation for replacing it.
; Keyboard "at" sign [''' @ '''] : On 24 May 2004 – the 160th anniversary of the first public Morse telegraph transmission – the Radiocommunication Bureau of the International Telecommunication Union ([[ITU-R]]) formally added the [''' @ '''] ("[[commercial at]]" or "commat") character to the official Morse character set, using the sequence denoted by the {{sc| {{overline|AC}} }} digraph: {{morse|dot|dash|dash|dot|dash|dot}} .<ref name=ITU-R-M-1677/><ref name=ARRL-News-2003-12-10/>
: This sequence was reported to have been chosen to represent "A[t] C[ommercial]", or a {{nobr|letter 'a'}} inside a swirl represented by a {{nobr|letter 'C'.}} The new character facilitates sending [[email|e‑mail]] addresses by Morse code, and is notable since it is the first official addition to the Morse set of characters since [[World War I]].<ref name=ARRL-News-2003-12-10/>
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