Morse code is atelecommunications method whichencodestext characters as standardized sequences of two different signal durations, calleddots anddashes, ordits anddahs.[3][4] Morse code is named afterSamuel Morse, one of the early developers of the system adopted forelectrical telegraphy.
International Morse code encodes the 26 basic Latin lettersA toZ, oneaccented Latin letter (É), theArabic numerals, and a small set of punctuation and procedural signals (prosigns). There is no distinction between upper and lower case letters.[1] Each Morse code symbol is formed by a sequence ofdits anddahs. Thedit duration can vary for signal clarity and operator skill, but for any one message, once established it is the basic unit of time measurement in Morse code. The duration of adah is three times the duration of adit (although some telegraphers deliberately exaggerate the length of adah for clearer signalling). Eachdit ordah within an encoded character is followed by a period of signal absence, called aspace, equal to thedit duration. The letters of a word areseparated by a space of duration equal to threedits, and words are separated by a space equal to sevendits.[1][5][a]
Morse code can be memorized and sent in a form perceptible to the human senses, e.g. via sound waves or visible light, such that it can be directly interpreted by persons trained in the skill.[7][8] Morse code is usually transmitted byon-off keying of an information-carrying medium such as electric current, radio waves, visible light, or sound waves.[9][10] The current or wave is present during the time period of thedit ordah and absent during the time betweendits anddahs.[11][12]
Since many natural languages use more than the 26 letters of theLatin alphabet,Morse alphabets have been developed for those languages, largely by transliteration of existing codes.[13]
To increase the efficiency of transmission, Morse code was originally designed so that the duration of each symbol is approximatelyinverse to the frequency of occurrence of the character that it represents in text of the English language. Thus the most common letter in English, the letterE, has the shortest code – a singledit. Because the Morse code elements are specified by proportion rather than specific time durations, the code is usually transmitted at the highest rate that the receiver is capable of decoding. Morse code transmission rate (speed) is specified ingroups per minute, commonly referred to aswords per minute.[b][7]
Early in the nineteenth century, European experimenters made progress with electrical signaling systems, using a variety of techniques includingstatic electricity and electricity fromVoltaic piles producingelectrochemical andelectromagnetic changes. These experimental designs were precursors to practical telegraphic applications.[14]
Telegraph key andsounder; the signal is "on" when the knob is pressed, and "off" when it is released, length and timing of thedits anddahs are entirely controlled by thetelegraphist
Following the discovery ofelectromagnetism byHans Christian Ørsted in 1820 and the invention of theelectromagnet byWilliam Sturgeon in 1824, there were developments inelectromagnetic telegraphy in Europe and America. Pulses ofelectric current were sent along wires to control an electromagnet in the receiving instrument. Many of the earliest telegraph systems used a single-needle system which gave a very simple and robust instrument. However, it was slow, as the receiving operator had to alternate between looking at the needle and writing down the message. In Morse code, a deflection of the needle to the left corresponded to adit and a deflection to the right to adah.[15] The needle clicked each time it moved to the right or left. By making the two clicks sound different (by installing one ivory and one metal stop), transmissions on the single needle device became audible as well as visible, which led in turn to theDouble PlateSounder System.[16]
William Cooke andCharles Wheatstone inBritain developed an electrical telegraph that used electromagnets in its receivers. They obtained an English patent in June 1837 and demonstrated it on the London and Birmingham Railway, making it the first commercial telegraph.Carl Friedrich Gauss andWilhelm Eduard Weber (1833) as well asCarl August von Steinheil (1837) used codes with varying word lengths for their telegraph systems.[17] In 1841, Cooke and Wheatstone built a telegraph that printed the letters from a wheel of typefaces struck by a hammer.[18]: 79
The American artistSamuel Morse, the AmericanphysicistJoseph Henry, and mechanical engineerAlfred Vail developed anelectrical 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.[18]: 79
The Morse system fortelegraphy, which was first used in about 1844, was designed to make indentations on a paper tape when electric currents were received. Morse's original telegraph receiver used a mechanical clockwork to move a paper tape. When an electrical current was received, an electromagnet engaged an armature that pushed a stylus onto the moving paper tape, making an indentation on the tape. When the current was interrupted, a spring retracted the stylus and that portion of the moving tape remained unmarked. Morse code was developed so that operators could translate the indentations marked on the paper tape into text messages.
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 byAlfred Vail in 1840 to include letters and special characters, so it could be used more generally. Vail estimated the frequency of use of letters in theEnglish language by counting the movable type he found in the type-cases of a local newspaper inMorristown, New Jersey.[18]: 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 asMorse landline code,American Morse code, orRailroad Morse, until the end of railroad telegraphy in the U.S. in the 1970s.[citation needed]
Operator-led change from graphical to audible code
In the original Morse telegraph system, the receiver's armature made a clicking noise as it moved in and out of position to mark the paper tape. Early telegraph operators soon learned that they could translate the clicks directly into dots and dashes, and write these down by hand, thus making the paper tape unnecessary. When Morse code was adapted toradio communication, the dots and dashes were sent as short and long tone pulses.
Later telegraphy training found that people become more proficient at receiving Morse code when it is taught "like a language", with each code perceived as a whole "word" instead of a sequence of separate dots and dashes, such as might be shown on a page.[19]
With the advent of tones produced by radiotelegraph receivers, the operators began to vocalize a dot asdit, and a dash asdah, to reflect the sounds of Morse code they heard. To conform to normal sending speed,dits which are not the last element of a code became voiced asdi. For example, theletterL ( ▄ ▄▄▄ ▄ ▄ ) is voiced asdi dah di dit.[20][21] Morse code was sometimes facetiously known as "iddy-umpty", adit lampooned as "iddy" and adah as "umpty", leading to the word "umpteen".[22]
Comparison of historical versions of Morse code with the current standard.Left: LaterAmerican Morse code from 1844.[17]Center: The modified and rationalized version used byFriedrich Gerke on German railways.Right: CurrentITU standard.
The Morse code, as specified in the current international standard,International Morse Code Recommendation,ITU-R M.1677-1,[1] was derived from a much-improved proposal byFriedrich Gerke in 1848 that became known as the "Hamburg alphabet", its only real defect being the use of an excessively long code ( ▄ ▄▄▄ ▄ ▄ ▄ and later the equal duration code ▄▄▄ ▄▄▄ ▄▄▄ ) for the frequently used vowelO.
Gerke changed many of the codepoints, in the process doing away with the different length dashes and different inter-element spaces ofAmerican Morse, leaving only two coding elements, the dot and the dash. Codes forGermanumlauted vowels andCH were introduced. Gerke's code was adopted in Germany and Austria in 1851.[23]
This finally led to the International Morse code in 1865. The International Morse code adopted most of Gerke's codepoints. The codes forO andP were taken from a code system developed by Steinheil. A new codepoint was added forJ since Gerke did not distinguish betweenI andJ. Changes were also made toX,Y, andZ. This left only four codepoints identical to the original Morse code, namelyE,H,K andN, and the latter two had theirdahs extended to full length. The original American code being compared dates to 1838; the later American code shown in the table was developed in 1844.[17]
In the 1890s, Morse code began to be used extensively for earlyradio communication before it was possible to transmit voice. In the late 19th and early 20th centuries, most high-speed international communication used Morse code on telegraph lines, undersea cables, and radio circuits.
Although previous transmitters were bulky and thespark gap system of transmission was dangerous and difficult to use, there had been some early attempts: In 1910, the U.S. Navy experimented with sending Morse from an airplane.[24] However the first regular aviation radiotelegraphy was onairships, which had space to accommodate the large, heavy radio equipment then in use. The same year, 1910, a radio on the airshipAmerica was instrumental in coordinating the rescue of its crew.[25]
DuringWorld War I,Zeppelin airships equipped with radio were used for bombing and naval scouting,[26] and ground-based radio direction finders were used for airship navigation.[26] Allied airships and military aircraft also made some use of radiotelegraphy.
However, there was little aeronautical radio in general use duringWorld War I, and in the 1920s, there was no radio system used by such important flights as that ofCharles Lindbergh fromNew York toParis in 1927. Once he and theSpirit of St. Louis were off the ground, Lindbergh was truly incommunicado and alone. Morse code in aviation began regular use in the mid-1920s. By 1928, when the first airplane flight was made by theSouthern Cross from California to Australia, one of its four crewmen was a radio operator who communicated with ground stations viaradio telegraph.
Beginning in the 1930s, both civilian and military pilots were required to be able to use Morse code, both for use with early communications systems and for identification of navigational beacons that transmitted continuous two- or three-letter identifiers in Morse code.Aeronautical charts show the identifier of each navigational aid next to its location on the map.
In addition, rapidly moving field armies could not have fought effectively without radiotelegraphy; they moved more quickly than their communications services could put up new telegraph and telephone lines. This was seen especially in theblitzkrieg offensives of theNazi GermanWehrmacht inPoland,Belgium,France (in 1940), theSoviet Union, and inNorth Africa; by theBritish Army inNorth Africa,Italy, and theNetherlands; and by theU.S. Army in France and Belgium (in 1944), and in southern Germany in 1945.
A U.S. Navy Morse Code training class in 2015. The sailors will use their new skills to collectsignals intelligence.
Radiotelegraphy using Morse code was vital duringWorld War II, especially in carrying messages between thewarships and thenaval bases of the belligerents. Long-range ship-to-ship communication was by radio telegraphy, usingencrypted messages because the voice radio systems on ships then were quite limited in both their range and their security. Radiotelegraphy was also extensively used bywarplanes, especially by long-rangepatrol planes that were sent out by navies to scout for enemy warships, cargo ships, and troop ships.
Morse code was used as an international standard for maritime distress until 1999 when it was replaced by theGlobal Maritime Distress and Safety System. When theFrench Navy ceased using Morse code on January 31, 1997, the final message transmitted was"Calling all. This is our last call before our eternal silence."[27]
In the United States the final commercial Morse code transmission was on July 12, 1999, signing off with Samuel Morse's original 1844 message,WHAT HATH GOD WROUGHT, and theprosignSK ("end of contact").[28]
TheUnited States Coast Guard has ceased all use of Morse code on the radio, and no longer monitors anyradio frequencies for Morse code transmissions, including the internationalmedium frequency (MF) distress frequency of500 kHz.[30] However, theFederal Communications Commission still grants commercial radiotelegraph operator licenses to applicants who pass its code and written tests.[31] Licensees have reactivated the old California coastal Morse stationKPH and regularly transmit from the site under either thiscall sign or as KSM. Similarly, a few U.S.museum ship stations are operated by Morse enthusiasts.[32]
A commercially manufactured iambic paddle used in conjunction with an electronic keyer to generate high-speed Morse code, the timing of which is controlled by the electronic keyer.[c]
Morse code speed is measured inwords per minute (WPM) or characters per minute (CPM). Characters have differing lengths because they contain differing numbers ofdits anddahs. Consequently, words also have different lengths in terms of dot duration, even when they contain the same number of characters. For this reason, some standard word is adopted for measuring operators' transmission speeds: Two such standard words in common use arePARIS andCODEX.[33] Operators skilled in Morse code can often understand ("copy") code in their heads at rates in excess of 40 WPM.
In addition to knowing, understanding, and being able to copy the standard written alpha-numeric and punctuation characters or symbols at high speeds, skilled high-speed operators must also be fully knowledgeable of all of the special unwritten Morse code symbols for the standardProsigns for Morse code and the meanings of these special procedural signals in standard Morse codecommunications protocol.
International contests in code copying are still occasionally held. In July 1939 at a contest inAsheville, North Carolina in the United States, Theodore Roosevelt McElroy (W1JYN) set a still-standing record for Morse copying, 75.2 WPM.[34] Pierpont (2004) also notes that some operators may have passed 100 WPM.[34] By this time, they are "hearing" phrases and sentences rather than words. The fastest speed ever sent by a straight key was achieved in 1942 by Harry Turner (W9YZE) (d. 1992) who reached 35 WPM in a demonstration at a U.S. Army base. To accurately compare code copying speed records of different eras it is useful to keep in mind that different standard words (50 dit durations versus 60 dit durations) and different interword gaps (5 dit durations versus 7 dit durations) may have been used when determining such speed records. For example, speeds run with theCODEX standard word and thePARIS standard may differ by up to 20%.
Today among amateur operators there are several organizations that recognize high-speed code ability, one group consisting of those who can copy Morse at 60 WPM.[35] Also, Certificates of Code Proficiency are issued by several amateur radio societies, including theAmerican Radio Relay League. Their basic award starts at 10 WPM with endorsements as high as 40 WPM, and are available to anyone who can copy the transmitted text. Members of theBoy Scouts of America may put a Morse interpreter's strip on their uniforms if they meet the standards for translating code at 5 WPM.
A U.S. Navysignalman sends Morse code signals in 2005.
Through May 2013, the First, Second, and Third Class (commercial) Radiotelegraph Licenses using code tests based upon theCODEX standard word were still being issued in the United States by the Federal Communications Commission. The First Class license required 20 WPM code group and 25 WPM text code proficiency, the others 16 WPM code group test (five letter blocks sent as simulation of receiving encrypted text) and 20 WPM code text (plain language) test. It was also necessary to pass written tests on operating practice and electronics theory. A unique additional demand for the First Class was a requirement of a year of experience for operators of shipboard and coast stations using Morse. This allowed the holder to be chief operator on board a passenger ship. However, since 1999 the use of satellite and very high-frequency maritime communications systems (GMDSS) has made them obsolete. (By that point meeting experience requirement for the First was very difficult.)
Currently, only one class of license, the Radiotelegraph Operator License, is issued. This is granted either when the tests are passed or as the Second and First are renewed and become this lifetime license. For new applicants, it requires passing a written examination on electronic theory and radiotelegraphy practices, as well as 16 WPM code-group and 20 WPM text tests. However, the code exams are currently waived for holders of Amateur Extra Class licenses who obtained their operating privileges under the old 20 WPM test requirement.
Morse codes of one version or another have been in use for more than 160 years — longer than any otherelectrical 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, orcontinental code, was created byFriedrich Clemens Gerke in 1848 and initially used for telegraphy betweenHamburg andCuxhaven in Germany. Gerke changed nearly half of the alphabet and all of thenumerals, 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 theInternational Telecommunication Union (ITU). Morse and Vail's final code specification, however, was only really used only 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 asAmerican Morse code orrailroad code, and is now almost never used, with the possible exception of historical re-enactments.
Inaviation, pilots useradio 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, theVOR-DME based atVilo Acuña Airport inCayo Largo del Sur, Cuba is identified by "UCL", and Morse codeUCL is repeatedly transmitted on its radio frequency.
In some countries, during periods of maintenance, the facility may instead transmit the signalTEST ( ▄▄▄ ▄ ▄ ▄ ▄ ▄▄▄ ), or theidentification may be removed, which tellspilots andnavigators that the station is unreliable. In Canada, the identification is removed entirely to signify the navigation aid is not to be used.[36][37]
In the aviation service, Morse is typically sent at a very slow speed of about 5 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.
The sound of non-directional beaconWG, on 248 kHz, located at 49.8992 North, 97.349197 West,[38] nearWinnipeg's main airport
Vibroplex brand semiautomatic key[d] (informally called a "bug" since it vaguely resembles astick insect).
International Morse code today is most popular amongamateur radio operators, in the mode commonly referred to as "continuous wave" or "CW".[e]Other, faster keying methods are available in radio telegraphy, such asfrequency-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, theInternational Telecommunication Union mandated Morse code proficiency as part of the amateur radio licensing procedure worldwide. However, theWorld Radiocommunication Conference of 2003 made the Morse code requirement for amateur radio licensing optional.[39] Many countries subsequently removed the Morse requirement from their license requirements.[40]
Until 1991, a demonstration of the ability to send and receive Morse code at a minimum of five words per minute (WPM) was required to receive an amateur radio license for use in the United States from theFederal Communications Commission. Demonstration of this ability was still required for the privilege to use theshortwave bands. Until 2000, proficiency at the 20 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 WPM.[41] 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:LF,MF low,MF high,HF,VHF, andUHF. In some countries, certain portions of the amateur radio bands are reserved for transmission of Morse code signals only.
Because Morse code transmissions employ anon-off keyed radio signal, it requires less complex equipment than otherradio transmission modes. Morse code also uses lessbandwidth (typically only 100–150 Hz wide, although only for a slow data rate) than voice communication (roughly 2,400~2,800 Hz used bySSB 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] This efficiency makes CW extremely useful forDX (long distance) transmissions, as well as for low-power transmissions (commonly called "QRP operation", from theQ-code for "reduce power"). There are several amateur clubs that require solid high speed copy, the highest of these has a standard of 60 WPM. TheAmerican Radio Relay League offers a code proficiency certification program that starts at 10 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 codes, and a set ofMorse code abbreviations for typical message components. For example,CQ is broadcast to be interpreted as "seek you" (I'd like to converse with anyone who can hear my signal). The abbreviationsOM (old man),YL (young lady), andXYL ("ex-young lady" – wife) are common.YL orOM is used by an operator when referring to the other operator (regardless of their actual age), andXYL orOM (rather than the expectedXYM) is used by an operator when referring to his or her spouse.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 traditionaltelegraph key (straight key) is still used by some amateurs, the use of mechanical semi-automatickeyers[d](informally called "bugs"), and of fully automatic electronickeyers (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. TheARRL has a readability standard for robot encoders calledARRL Farnsworth spacing[42] that is supposed to have higher readability for both robot and human decoders. Some programs like WinMorse[43] have implemented the standard.
Radio navigation aids such asVORs andNDBs for aeronautical use broadcast identifying information in the form of Morse Code, though manyVOR stations now also provide voice identification.[44] Warships, including those of theU.S. Navy, have long usedsignal lamps to exchange messages in Morse code. Modern use continues, in part, as a way to communicate while maintainingradio silence.
An important application is signalling for help throughSOS, " ▄ ▄ ▄ ▄▄▄ ▄▄▄ ▄▄▄ ▄ ▄ ▄ ". This can be sent many ways: keying a radio on and off, flashing a mirror, toggling a flashlight, and similar methods. TheSOS signal is not sent as three separate characters; rather, it is aprosignSOS, and is keyed without gaps between characters.[45]
Morse code has been employed as anassistive technology, helping people with a variety ofdisabilities to communicate.[46][47][f][49] For example, the Android operating system versions 5.0 and higher allow users to input text using Morse Code as an alternative to a keypad orhandwriting recognition.[50]
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.[51]
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 overrow 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 magazineQST,[52] an old shipboard radio operator who had astroke 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 inQST magazine.[53][54] Another example occurred in 1966 whenprisoner of warJeremiah Denton, brought on television by hisNorth Vietnamese captors, Morse-blinked the wordTORTURE. In these two cases, interpreters were available to understand those series of eye-blinks.
Morse code can be transmitted in a number of ways: Originally as electrical pulses along atelegraph 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 anAldis lamp or aheliograph, 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 adah. Ground forces send messages to aircraft with panel signalling, where a horizontal panel is a dah and a vertical panel a dit.[55]
Morse messages are generally transmitted by a hand-operated device such as atelegraph 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 shorterdahs 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.
Morse code is transmitted using just two states (on and off). Morse code may be represented as a binary code, and that is what telegraph operators do when transmitting messages. Working from the above ITU definition and further defining abit as a dot time, a Morse code sequence may be crudely represented a combination of the following five bit-strings:
short mark, dot ordit ( ▄ ): '1'b
longer mark, dash ordah ( ▄▄▄ ): '111'b
intra-character gap (between thedits anddahs within a character): 0
short gap (between letters): '000'b
medium gap (between words): '0000000'b
The marks and gaps alternate:Dits anddahs are always separated by one of the gaps, and that the gaps are always separated by adit or adah.
A more efficient binary encoding uses only two-bits for eachdit ordah element, with the 1 dit-length pause that must follow after each automatically included for every 2 bit code. One possible coding is by number value for the length of signal tone sent one could use '01'b for adit and the automatic single-dit pause after it, and '11'b for adah and the automatic single-dit following pause, and '00'b for theextra pause between letters (in effect, an end-of-letter mark). That leaves the code '10'b available for some other purpose, such as an escape character, or to more compactly represent theextra space between words (an end-of-word mark) instead of '00 00 00'b (only 6 dit lengths, since the 7th is automatically inserted as part of the priordit ordah). Although thedit and inter-letter pauses work out to be the same, for any letter containing adah, the two-bit encoding uses digital memory more compactly than the direct-conversion bit strings mentioned above. Including the letter-separating spaces, all International Morse letter codes pack into 12 bits or less (5 symbols), and most fit into 10 bits or less (4 symbols); most of theprocedural signs fit into 14 bits, with a few only needing 12 bits (5 symbols); and all digits require exactly 12 bits.
For example, MorseG ( ▄▄▄ ▄▄▄ ▄ + 2 extra empty dits for "end of letter") would binary-encode as '11'b, '11'b, '01'b, '00'b; when packed it is '1111 0100'b = 'F4'x, which stores into only onebyte (twonibbles) (as does every three-element code). The bit encoding for the longer method mentioned earlier the same letter would encode as '1110'b, '1110'b, '1000'b = '1110 1110 1000'b = 'EE8'x, or one-and-a-half bytes (three nibbles). The space saving allows small devices, like portable memory keyers, to have more and longer International Morse code sequences in small, conventional device-drivermicroprocessors'RAM chips.
The very longtime constants of 19th and early 20th centurysubmarine communications cables required a different form of Morse signalling. Instead of keying a voltage on and off for varying times, the dits and dahs were represented by two polarities of voltage impressed on the cable, for a uniform time.[56]
Below is an illustration of timing conventions. The phraseMORSE CODE, in Morse code format, would normally be written something like this, where– representsdahs and· representsdits:
−− −−− ·−· ··· · −·−· −−− −·· · M O R S E C O D E
Next is the exact conventional timing for this phrase, with ▓ representing "signal on", and˽ representing "signal off", each for the time length of exactly one dit:
1 2 3 4 5 6 7 8 12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789 ———M——— —————O————— ———R——— ——S—— E —————C————— —————O————— ———D——— E ▓▓▓˽▓▓▓˽˽˽▓▓▓˽▓▓▓˽▓▓▓˽˽˽▓˽▓▓▓˽▓˽˽˽▓˽▓˽▓˽˽˽▓˽˽˽˽˽˽˽▓▓▓˽▓˽▓▓▓˽▓˽˽˽▓▓▓˽▓▓▓˽▓▓▓˽˽˽▓▓▓˽▓˽▓˽˽˽▓ ↑ ↑ ↑ ↑ ↑ | dah dit | | symbol space letter space word space
Morse code is often spoken or written withdah for dashes,dit for dots located at the end of a character, anddi for dots located at the beginning or internally within the character. Thus, the following Morse code sequence:
M O R S E C O D E−− −−− ·−· ··· · (space) −·−· −−− −·· ·
is spoken (or sung):
Dah dah dah dah dah di dah dit di di dit dit, Dah di dah dit dah dah dah dah di dit dit.
For use on radio, there is little point in learning to readwritten Morse as above; rather, thesounds of all of the letters and symbols need to be learned, for both sending and receiving.
All Morse code elements depend on the dot /dit length. Adah is the length of 3 dits (with no gaps between), and spacings are specified in number ofdit lengths. An unambiguous method of specifying the transmission speed is to specify thedit duration as, for example,50 milliseconds.
Specifying thedit duration is, however, not the common practice. Usually, speeds are stated in words per minute. That introduces ambiguity because words have different numbers of characters, and characters have differentdit lengths. It is not immediately clear how a specific word rate determines thedit duration in milliseconds.
Some method to standardize the transformation of a word rate to adit duration is useful. A simple way to do this is to choose adit duration that would send a typical word the desired number of times in one minute. If, for example, the operator wanted a character speed of 13 words per minute, the operator would choose adit rate that would send the typical word 13 times in exactly one minute.
The typical word thus determines thedit length. It is common to assume that a word is 5 characters long. There are two common typical words:PARIS andCODEX.PARIS mimics a word rate that is typical of natural language words and reflects the benefits of Morse code's shorter code durations for common characters such asE andT.CODEX offers a word rate that is typical of 5 letter code groups (sequences of random letters). Using the wordPARIS as a standard, the number ofdit units is 50 and a simple calculation shows that thedit length at 20 words per minute is60 milliseconds. Using the wordCODEX with 60 dit units, thedit length at 20 words per minute is50 milliseconds.
Because Morse code is usually sent by hand, it is unlikely that an operator could be that precise with thedit length, and the individual characteristics and preferences of the operators usually override the standards.
For commercial radiotelegraph licenses in the United States, the Federal Communications Commission specifies tests for Morse code proficiency in words per minute and in code groups per minute.[57]: §13.207(c), §13.209(d) TheFCC specifies that a "word" is 5 characters long. The Commission specifies Morse code test elements at 16 code groups per minute, 20 words per minute, 20 code groups per minute, and 25 words per minute.[57]: §13.203(b) The word per minute rate would be close to thePARIS standard, and the code groups per minute would be close to theCODEX standard.
While the Federal Communications Commission no longer requires Morse code for amateur radio licenses, the old requirements were similar to the requirements for commercial radiotelegraph licenses.[57]: §97.503, 1996
A difference between amateur radio licenses and commercial radiotelegraph licenses is that commercial operators must be able to receive code groups of random characters along with plain language text. For each class of license, the code group speed requirement is slower than the plain language text requirement. For example, for the Radiotelegraph Operator License, the examinee must pass a 20 word per minute plain text test and a 16 word per minute code group test.[31]
Based upon a 50 dit duration standard word such asPARIS, the time for onedit duration or one unit can be computed by the formula:
T =1,200/W
where:T is the unit time, ordit duration in milliseconds, andW is the speed inWPM.
Sometimes, especially while teaching Morse code, the timing rules above are changed so two different speeds are used: A character speed and a text speed. The character speed is how fast each individual letter is sent. The text speed is how fast the entire message is sent. For example, individual characters may be sent at a 13 words-per-minute rate, but the intercharacter and interword gaps may be lengthened so the word rate is only 5 words per minute.
Using different character and text speeds is, in fact, a common practice, and is used in the Farnsworth method oflearning Morse code.
Alternative display of common characters in International Morse code
International Morse codebinary search tree: The graph branches left for eachdit and right for eachdah until the character representation is reached. OfficialITU codes are shown as black letters on dark grey, and are complete, including punctuation; a few non-ITU extensions are shown in grey letters on light grey, but many others are left out. ITUprosigns are circled in red with red text and are complete; unofficial prosigns are orange and are mostly complete.
People learning Morse code using theFarnsworth method are taught to send and receive letters and other symbols at their full target speed, that is with normal relative timing of thedits,dahs, and spaces within each symbol for that speed. The Farnsworth method is named for Donald R. "Russ" Farnsworth, also known by hiscall sign, W6TTB. However, initially exaggerated spaces between symbols and words are used, to give "thinking time" to make the sound "shape" of the letters and symbols easier to learn. The spacing can then be reduced with practice and familiarity.
Another popular teaching method is theKoch method, invented in 1935 by the German engineer and formerstormtrooper Ludwig Koch,[59] which uses the full target speed from the outset but begins with just two characters. Once strings containing those two characters can be copied with 90% accuracy, an additional character is added, and so on until the full character set is mastered.
In North America, many thousands of individuals have increased their code recognition speed (after initial memorization of the characters) by listening to the regularly scheduled code practice transmissions broadcast byW1AW, the American Radio Relay League's headquarters station.[60] As of 2015,[update] the United States military taught Morse code as an 81-day self-paced course, having phased out more traditional classes.[61]
Visual mnemonic charts have been devised over the ages.Baden-Powell included one in theGirl Guides handbook[62] in 1918.
In the United Kingdom, many people learned the Morse code by means of a series of words or phrases that have the same rhythm as a Morse character. For instance,Q in Morse isdah dah di dah , which can be memorized by the phrase "God Save the Queen", and the Morse forF isdi di dah dit , which can be memorized as "Did she like it?"[g]
Letters, numbers, punctuation, prosigns for Morse code and non-Latin variants
Most numbers have an unofficial short-form, given in the table below. They are only used when both the sender and the receiver understand that numbers, and not letters, are intended;[citation needed] for example, one often sees the most commonR-S-T signal report rendered as5NN[‡] instead of599.[citation needed]
Codes that arenot cut numbers, or are not numbers, areshaded grey in the table.
[†]
There are no distinct cut-number codes for4 or6, since cut numbers come from reducing multipledahs in the standard Morse number codes to only onedah, but keeping all thedits as-is.
[‡]
Some operators just send the normal code for5, even when using other cut numbers, since fivedits are still fairly short (same duration as cut 3 and cut 7), and a singledit could possibly be misinterpreted as a mistaken cut 1 or cut decimal point.[citation needed]
Prosigns for Morse code are special (usually) unwritten procedural signals or symbols that are used to indicate changes incommunications protocol status orwhite space text formatting actions.
The symbols [!], [$], and [&] are not defined inside the officialITU-RInternational Morse Code Recommendation,[1] but informal conventions for them exist. (The [@] symbol was formally added in 2004.)
Exclamation mark
There is no standard representation for the exclamation mark [!], although theKWdigraph ( ▄▄▄ ▄ ▄▄▄ ▄ ▄▄▄ ▄▄▄ ) was proposed in the 1980s by theHeathkit Company.[l] While Morse code translation software prefers the Heathkit version, on-air use is not yet universal as some amateur radio operators in North America and the Caribbean continue to use the olderMN digraph ( ▄▄▄ ▄▄▄ ▄▄▄ ▄ )[m] copied over fromAmerican Morse landline code.
Currency symbols
The ITU has never formally codified anycurrency symbols into Morse code: The unambiguousISO 4217 currency codes are preferred for transmission.
The [$] sign code was represented in thePhillips Code[n] as two characters "SX", which became merged intoSX ( ▄ ▄ ▄ ▄▄▄ ▄ ▄ ▄▄▄ ).
Ampersand [&]
The suggested unofficial encoding of theampersand [&] sign listed above,[i] often shown asAS, is also the official Morseprosign forwait. In addition, theAmerican Morse encoding for an ampersand ( ▄ ▄ ▄ ▄ ) was similar toES ( ▄ ▄ ▄ ▄ ) andhams have nearly universally carried over this use as an abbreviation for "and" (e.g.WX HR COLD ES RAINYthe weather here is cold and rainy).
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 theAC digraph: ▄ ▄▄▄ ▄▄▄ ▄ ▄▄▄ ▄ .[1][66]
This sequence was reported to have been chosen to represent "A[t] C[ommercial]", or a letter "a" inside a swirl represented by a letter "C". The new character facilitates sendinge‑mail addresses by Morse code, and is notable since it is the first official addition to the Morse set of characters sinceWorld War I.[66]
The typical tactic for creating Morse codes fordiacritics and non-Latin alphabetic scripts has been to begin by simply using the International Morse codes used for letters whose sound matches the sound of the local alphabet. BecauseGerke code (the predecessor to International Morse) was in official use in central Europe,[23] and included four characters not included in the International Morse standard (Ä,Ö,Ü, andCH) it has served as a beginning-point for other languages that use analphabetic script, but require codes for letters not accommodated by International Morse.
The usual method has been to first transliterate the sounds represented by the International code and the four unique Gerke codes into the local alphabet, henceGreek, Hebrew,Russian, and Ukrainian Morse codes. If more codes are needed, one can either invent a new code or convert an otherwise unused code from either code set to the non-Latin letter. For example:
Ñ in Spanish Morse is ▄▄▄ ▄▄▄ ▄ ▄▄▄ ▄▄▄ , a language-specific code not used in either International or Gerke Morse.
For the Greek letterΨ,Greek Morse code uses the International Morse code forQ, ▄▄▄ ▄▄▄ ▄ ▄▄▄ , which has no corresponding letter in modern Greek;Ψ andQ have no historical, phonetic, or shape relationship.
ForRussian and Bulgarian,Russian Morse code is used to map the Cyrillic characters to four-element codes. Many of the characters are encoded the same as their latin-alphabet look-alikes or sound-alikes (A,O,E,I,T,M,N,R,K, etc.). The Bulgarian alphabet contains 30 characters, which exactly match all possible combinations of 1, 2, 3, and 4 dits anddahs (RussianЫ is used as BulgarianЬ, RussianЬ is used as BulgarianЪ). Russian requires two more codes, for lettersЭ andЪ which are each encoded with 5 elements.
Non-alphabetic scripts require more radical adaption. Japanese Morse code (Wabun code) has a separate encoding forkana script; although many of the codes are used for International Morse, the sounds they represent are mostly unrelated. The Japanese /Wabun code includes specialprosigns for switching back-and-forth from International Morse: ▄▄▄ ▄ ▄ ▄▄▄ ▄▄▄ ▄▄▄ signals a switch from International Morse toWabun, and ▄ ▄ ▄ ▄▄▄ ▄ to return fromWabun to International Morse.
ForChinese,Chinese telegraph code is used to mapChinese characters to four-digit codes and send these digits out using standard Morse code. Korean Morse code[67] uses the SKATS mapping, originally developed to allow Korean to be typed on western typewriters. SKATS mapshangul characters to arbitrary letters of theLatin script and has no relationship to pronunciation inKorean.
During early World War I (1914–1916), Germany briefly experimented with 'dotty' and 'dashy' Morse, in essence adding a dot or a dash at the end of each Morse symbol. Each one was quickly broken by Allied SIGINT, and standard Morse was resumed by Spring 1916. Only a small percentage of Western Front (North Atlantic andMediterranean Sea) traffic was in 'dotty' or 'dashy' Morse during the entire war. In popular culture, this is mostly remembered in the bookThe Codebreakers byDavid Kahn and in the national archives of the UK and Australia (whoseSIGINT operators copied most of this Morse variant). Kahn's cited sources come from the popular press and wireless magazines of the time.[68]
Other variations include forms of "fractional Morse" or "fractionated Morse", which recombine the characters of the Morse code–encoded message and then encrypt them using a cipher in order to disguise the text.[69]
Decoding software for Morse code ranges from software-defined wide-band radio receivers, coupled to the Reverse Beacon Network,[70] which decodes signals and detectsCQ messages onham bands, to smartphone applications.[71]
^Until 1949, words were separated by a space equal to fivedits.[6]
^The time needed to transmit the wordPARIS is typically used as the standard "word" for calculating the "word per minute" rate. Other standard "words" such asCODEX are also used.[7]
^These modern "iambic" keys are operated by one or two "paddles" pressed left and right, instead of pressing down a lever, as in the traditional telegraph keys, pictured at the start of this article. Operating paddle keys is similar to using the oldVibroplex clockwork telegraph keys: Pressing the paddle to the right generates a series of repeateddits until the paddle is released; pressing the paddle to the left produces a similar series ofdahs; and with two-paddle electronic keys, squeezing the two paddles from both sides produces an alternatingdit dah dit dah sequence.
For left-handed operators, the actions of the two paddles are often reversed.
^abThe semiautomatic key paddle, when pressed to the right by the thumb, kicks a clockwork-like horizontal pendulum that generates a series ofdits, 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 singledah, the length of which is controlled by the operator. Multipledahs require multiple presses. Left-handed operators may use a key built as a mirror image of this one.
^The namecontinuous wave was chosen to distinguish the single-frequencytransmission mode from the sliding-frequencydamped wave signals from now-bannedspark-gap transmitters. Although the modernON /OFF signal itself is interrupted, not continuous, it does (ideally) maintain a single, constant frequencycarrier wave throughout any one transmission.
^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)[48]
^A well-known Morse code rhythm from the Second World War period derives fromBeethoven'sFifth Symphony, the opening phrase of which was regularly played at the beginning of BBC broadcasts. The timing of the notes corresponds to the Morse forV,di di di dah ( ▄ ▄ ▄ ▄▄▄ ), understood as"'V' for Victory".[63][64]
^abcThe well-established standard abbreviation for "and" isE S, adapted from the code forampersand inRailroad Morse. The code forE S( ▄ ▄ ▄ ▄ ) is actually slightly shorter in duration than thewait prosign( ▄ ▄▄▄ ▄ ▄ ▄ ), so there is no motivative to replace it.
^Single-line decoding display may use printed "+" for message separator prosign.
^abcAlthough not strictly aLatin alphabet character, the code forÉ is part of theITU-R Morse code standard, and is the only accented character included in the recommendation.[1]
^Heathkit was a popular, long-standing vendor of kits for amateur radio equipment.
^MN orOE, ▄▄▄ ▄▄▄ ▄▄▄ ▄ , is shared with unofficialÖ,Ó, andØ used in some non-Latin alphabets.
^ThePhillips Code was a huge collection of abbreviations used on land line telegraphy.
^Telegraph Regulations(PDF) (Report). ITU History. Geneva, CH:International Telecommunication Union. 1949 [1947]. p. 42.the space between two words is equal to seven dots; — Annexed to theInternational Telecommunication Convention, Atlantic City, 1947; revised Paris, 1949.
^abTelegraph Regulations(PDF) (Report). ITU History. Geneva, CH:International Telecommunication Union. 1938 [1932]. p. 39.The space between two words is equal to five dots. — Annexed to theInternational Telecommunication Convention, Madrid, 1932; revised Cairo, 1938.
^Smith, W.W.; Dawley, Ray L.; et al., eds. (1940).The "Radio" Handbook (7th ed.). Santa Barbara, CA: Editors and Engineers Ltd. p. 178. Retrieved18 July 2022.
^Engineer-in-Chief's Office (1938) [1919]. Elementary Principles of Telegraphy and Systems up to Morse Duplex (Report). Technical Pamphlets for Workmen. London, UK: His Majesty's Stationery Office. p. 6.
^Freebody, J.W. (1959). "Historical survey of telegraphy".Telegraphy. London, UK: Sir Isaac Pitman & Sons, Ltd. pp. 28–29.
^abcBurns, R.W. (2004).Communications: An international history of the formative years. Institution of Electrical Engineers. pp. 79, 84.ISBN0-86341-327-7.
^abPierpont, William G. (13 May 2004) [2002].The Art & Skill of Radio Telegraphy(PDF).Archived(PDF) from the original on 26 February 2012. Retrieved14 June 2013 – via pcpractice.com.
^Baden-Powell, Robert (1938)."Girl Guiding"(PDF). Pearson. p. 61.Archived(PDF) from the original on 6 October 2015. Retrieved6 September 2015.Some people find it easier to remember the [dots] and dashes by picturing them as forming the letters ...(page 61)
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