Morse code

Morse code is a character encoding scheme used in telecommunication that encodes text characters as standardized sequences of two different signal durations called dots and dashes or dits and dahs.[2][3] Morse code is named for Samuel F. B. Morse, an inventor of the telegraph.

The International Morse Code encodes the ISO basic Latin alphabet, some extra Latin letters, the Arabic numerals and a small set of punctuation and procedural signals (prosigns).[1] Each Morse code symbol is formed by a sequence of dots and dashes. The dot duration is the basic unit of time measurement in Morse code transmission. The duration of a dash is three times the duration of a dot. Each dot or dash within a character is followed by period of signal absence, called a space, equal to the dot duration. The letters of a word are separated by a space of duration equal to three dots, and the words are separated by a space equal to seven dots.[1] To increase the efficiency of encoding, Morse code was designed so that the length of each symbol is approximately inverse to the frequency of occurrence in text of the English language character that it represents. Thus the most common letter in English, the letter "E", has the shortest code: a single dot. 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. The Morse code transmission rate (speed) is specified in groups per minute, commonly referred to as words per minute.[4]

Morse code is usually transmitted by on-off keying of an information carrying medium such as electric current, radio waves, visible light or sound waves.[5][6] The current or wave is present during time period of the dot or dash and absent during the time between dots and dashes.[7][8]

Morse code can be memorized, and Morse code signalling in a form perceptible to the human senses, such as sound waves or visible light, can be directly interpreted by persons trained in the skill.[9][10]

Because many non-English natural languages use other than the 26 Roman letters, Morse alphabets have been developed for those languages.[11]

SOS, the standard emergency signal, is a Morse code prosign

In an emergency, Morse code can be generated by improvised methods such as turning a light on and off, tapping on an object or sounding a horn or whistle, making it one of the simplest and most versatile methods of telecommunication. The most common distress signal is SOS – three dots, three dashes, and three dots – internationally recognized by treaty.

International Morse Code
Chart of the Morse code 26 letters and 10 numerals.[1]

Development and history

Typical "straight key". This U.S. model J-38, was manufactured in huge quantities during World War II. The signal is "on" when the knob is pressed, and "off" when it is released. Length and timing of the dots and dashes are entirely controlled by the telegraphist.
Morse Code Receiver
Morse code receiver, recording on paper tape

Beginning in 1836, the American artist Samuel F. B. Morse, the American physicist Joseph Henry, and Alfred Vail developed an electrical telegraph system. This system sent pulses of electric current along wires which controlled an electromagnet that was located at the receiving end of the telegraph system. A code was needed to transmit natural language using only these pulses, and the silence between them. Around 1837, Morse, therefore, developed an early forerunner to the modern International Morse code. Around the same time, Carl Friedrich Gauss and Wilhelm Eduard Weber (1833) as well as Carl August von Steinheil (1837) had already used codes with varying word lengths for their telegraphs. Since around 1800, European experimenters had been making progress with earlier battery-powered signaling systems in emitting oxygen and hydrogen bubbles through liquid, flipping magnetic semaphore flags, tripping alarms across long distances over wire, and other techniques. The numerous ingenious experimental encoding designs they devised and demonstrated were telegraphic precursors to practical applications.[12]

In 1837, William Cooke and Charles Wheatstone in England began using an electrical telegraph that also used electromagnets in its receivers. However, in contrast with any system of making sounds of clicks, their system used pointing needles that rotated above alphabetical charts to indicate the letters that were being sent. In 1841, Cooke and Wheatstone built a telegraph that printed the letters from a wheel of typefaces struck by a hammer. This machine was based on their 1840 telegraph and worked well; however, they failed to find customers for this system and only two examples were ever built.[13]

On the other hand, the Morse system for telegraphy, 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.

The Morse code was developed so that operators could translate the indentations marked on the paper tape into text messages. In his earliest 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 frequency of use of letters in the English language by counting the movable type he found in the type-cases of a local newspaper in Morristown.[14] The shorter marks were called "dots", and the longer ones "dashes", and the letters most commonly used were assigned the shorter sequences of dots and dashes. This code was used since 1844 and became known as Morse landline code or American Morse code.

Morse comparison
Comparison of historical versions of Morse code with the current standard. 1. American Morse code as originally defined. 2. The modified and rationalized version used by Gerke on German railways. 3. The current ITU standard.

In the original Morse telegraphs, the receiver's armature made a clicking noise as it moved in and out of position to mark the paper tape. The 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 to radio communication, the dots and dashes were sent as short and long tone pulses. It was later found that people become more proficient at receiving Morse code when it is taught as a language that is heard, instead of one read from a page.[15]

To reflect the sounds of Morse code receivers, the operators began to vocalize a dot as "dit", and a dash as "dah". Dots which are not the final element of a character became vocalized as "di". For example, the letter "c" was then vocalized as "dah-di-dah-dit".[16][17] Morse code was sometimes facetiously known as "iddy-umpty", and a dash as "umpty", leading to the word "umpteen".[18]

The Morse code, as it is used internationally today, was derived from a much refined proposal which became known as "Hamburg alphabet" by Friedrich Clemens Gerke in 1848. It was adopted by the Deutsch-Österreichischer Telegraphenverein (German-Austrian Telegraph Society) in 1851. This finally led to the International Morse code in 1865.

In the 1890s, Morse code began to be used extensively for early radio 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. In aviation, Morse code in radio systems started to be used on a regular basis in the 1920s. Although previous transmitters were bulky and the spark gap system of transmission was difficult to use, there had been some earlier attempts. In 1910, the US Navy experimented with sending Morse from an airplane.[19] That same year, a radio on the airship America had been instrumental in coordinating the rescue of its crew.[20] Zeppelin airships equipped with radio were used for bombing and naval scouting during World War I,[21] and ground-based radio direction finders were used for airship navigation.[21] Allied airships and military aircraft also made some use of radiotelegraphy. However, there was little aeronautical radio in general use during World War I, and in the 1920s, there was no radio system used by such important flights as that of Charles Lindbergh from New York to Paris in 1927. Once he and the Spirit of St. Louis were off the ground, Lindbergh was truly alone and incommunicado. On the other hand, when the first airplane flight was made from California to Australia in 1928 on the Southern Cross, one of its four crewmen was its radio operator who communicated with ground stations via radio 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 which 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.

Radiotelegraphy using Morse code was vital during World War II, especially in carrying messages between the warships and the naval bases of the belligerents. Long-range ship-to-ship communication was by radio telegraphy, using encrypted messages because the voice radio systems on ships then were quite limited in both their range and their security. Radiotelegraphy was also extensively used by warplanes, especially by long-range patrol planes that were sent out by those navies to scout for enemy warships, cargo ships, and troop ships.

In addition, rapidly moving armies in the field could not have fought effectively without radiotelegraphy because they moved more rapidly than telegraph and telephone lines could be erected. This was seen especially in the blitzkrieg offensives of the Nazi German Wehrmacht in Poland, Belgium, France (in 1940), the Soviet Union, and in North Africa; by the British Army in North Africa, Italy, and the Netherlands; and by the U.S. Army in France and Belgium (in 1944), and in southern Germany in 1945.

U.S. Navy 151103-N-XX082-001 Morse Code training 2015
A U.S. Navy Morse Code training class in 2015. The sailors will use their new skills to collect signals intelligence.

Morse code was used as an international standard for maritime distress until 1999 when it was replaced by the Global Maritime Distress Safety System. When the French Navy ceased using Morse code on January 31, 1997, the final message transmitted was "Calling all. This is our last cry before our eternal silence."[22] 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 the prosign "SK".[23]

As of 2015, the United States Air Force still trains ten people a year in Morse.[24] The United States Coast Guard has ceased all use of Morse code on the radio, and no longer monitors any radio frequencies for Morse code transmissions, including the international medium frequency (MF) distress frequency of 500 kHz.[25] However, the Federal Communications Commission still grants commercial radiotelegraph operator licenses to applicants who pass its code and written tests.[26] Licensees have reactivated the old California coastal Morse station KPH and regularly transmit from the site under either this Call sign or as KSM. Similarly, a few US Museum ship stations are operated by Morse enthusiasts.[27]

User proficiency

Bencher paddle
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. Manipulation of dual-lever paddles is similar to the Vibroplex, but pressing the right paddle generates a series of dahs, and squeezing the paddles produces dit-dah-dit-dah sequence. The actions are reversed for left-handed operators.

Morse code speed is measured in words per minute (wpm) or characters per minute (cpm). Characters have differing lengths because they contain differing numbers of dots and dashes. Consequently, words also have different lengths in terms of dot duration, even when they contain the same number of characters. For this reason, a standard word is helpful to measure operator transmission speed. "PARIS" and "CODEX" are two such standard words.[28] 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 standard Prosigns for Morse code and the meanings of these special procedural signals in standard Morse code communications protocol.

International contests in code copying are still occasionally held. In July 1939 at a contest in Asheville, North Carolina in the United States Ted R. McElroy set a still-standing record for Morse copying, 75.2 wpm.[29] William Pierpont N0HFF also notes that some operators may have passed 100 wpm.[29] 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 dot durations versus 60 dot durations) and different interword gaps (5 dot durations versus 7 dot durations) may have been used when determining such speed records. For example, speeds run with the CODEX standard word and the PARIS 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.[30] Also, Certificates of Code Proficiency are issued by several amateur radio societies, including the American 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 the Boy Scouts of America may put a Morse interpreter's strip on their uniforms if they meet the standards for translating code at 5 wpm.

International Morse Code

Morse code has been in use for more than 160 years—longer than any other electrical coding 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 numerals, providing the foundation for the modern form of the code. After some minor changes, International Morse Code was standardized at the International Telegraphy Congress in 1865 in Paris and was later made the standard by the International Telecommunication Union (ITU). Morse's original code specification, largely limited to use in the United States and Canada, became known as American Morse code or railroad code. American Morse code is now seldom used except in historical re-enactments.


VFR Chart Cayo Largo Del Sur VOR-DME
Cayo Largo Del Sur VOR-DME.

In aviation, pilots use radio navigation aids. To ensure that the stations the pilots are using 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 VOR-DME based at Vilo Acuña Airport in Cayo Largo del Sur, Cuba is coded as "UCL", and UCL in Morse code is transmitted on its radio frequency. In some countries, during periods of maintenance, the facility may radiate a T-E-S-T code (▄▄▄▄▄▄▄▄) or the code may be removed which tells pilots and navigators that the station is unreliable. In Canada, the identification is removed entirely to signify the navigation aid is not to be used.[31][32] 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 beacon WG, on 248 kHz, located at 49.8992 North, 97.349197 West,[33] near Winnipeg's main airport

Amateur radio

Vibroplex brand semiautomatic key (generically called a "bug"). The paddle, when pressed to the right by the thumb, generates a series of dits, the length and timing of which are controlled by a sliding 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 use a key built as a mirror image of this one.

International Morse code today is most popular among amateur radio operators, in the mode commonly referred to as "continuous wave" or "CW". (This name was chosen to distinguish it from the damped wave emissions from spark transmitters, not because the transmission is continuous.) Other keying methods are available in radio telegraphy, such as frequency shift keying.

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.[34] Many countries subsequently removed the Morse requirement from their licence requirements.[35]

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 the Federal Communications Commission. Demonstration of this ability was still required for the privilege to use the HF 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, the FCC reduced the Extra Class requirement to five wpm.[36] 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, HF, VHF, and UHF. In some countries, certain portions of the amateur radio bands are reserved for transmission of Morse code signals only.

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 of Morse 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). OM (old man), YL (young lady) and XYL ("ex-YL" – wife) are common abbreviations. YL or OM is used by an operator when referring to the other operator, XYL or OM is used by an operator when referring to his or her spouse. QTH is "location" ("My QTH" 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 keyers (known as "bugs") and of fully automatic electronic keyers is prevalent today. Software is also frequently employed to produce and decode Morse code radio signals.

Many amateur radio repeaters identify with Morse, even though they are used for voice communications.

Other uses

Seaman send Morse code signals
A U.S. Navy signalman sends Morse code signals in 2005.

Through May 2013, the First, Second, and Third Class (commercial) Radiotelegraph Licenses using code tests based upon the CODEX 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 codegroup 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.

Radio navigation aids such as VORs and NDBs for aeronautical use broadcast identifying information in the form of Morse Code, though many VOR stations now also provide voice identification.[37] Warships, including those of the U.S. Navy, have long used signal lamps to exchange messages in Morse code. Modern use continues, in part, as a way to communicate while maintaining radio silence.

ATIS (Automatic Transmitter Identification System) uses Morse code to identify uplink sources of analog satellite transmissions.

Applications for the general public

Representation of SOS-Morse code.

An important application is signalling for help through SOS, "▄▄▄▄▄▄▄▄▄▄▄". This can be sent many ways: keying a radio on and off, flashing a mirror, toggling a flashlight, and similar methods. SOS is not three separate characters, rather, it is a prosign SOS, and is keyed without gaps between characters.[38]

Some Nokia mobile phones offer an option to alert the user of an incoming text message with the Morse tone "▄▄▄▄▄▄▄▄" (representing SMS or Short Message Service).[39] In addition, applications are now available for mobile phones that enable short messages to be input in Morse Code.[40]

Morse code as an assistive technology

Morse code has been employed as an assistive technology, helping people with a variety of disabilities to communicate. 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 or handwriting recognition.[41]

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, Newell and 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 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,[42] 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, [43][44] Another example occurred in 1966 when prisoner of war Jeremiah Denton, brought on television by his North Vietnamese captors, Morse-blinked the word TORTURE. In these two cases, interpreters were available to understand those series of eye-blinks.

Representation, timing, and speeds

International Morse code is composed of five elements:[1]

  1. short mark, dot or "dit" (▄▄): "dot duration" is one time unit long
  2. longer mark, dash or "dah" (▄▄▄▄▄): three time units long
  3. inter-element gap between the dots and dashes within a character: one dot duration or one unit long
  4. short gap (between letters): three time units long
  5. medium gap (between words): seven time units long


Morse code can be transmitted in a number of ways: originally as electrical pulses along a telegraph wire, but also as an audio tone, a radio signal with short and long 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 dash.

Morse code is transmitted using just two states (on and off). Historians have called it the first digital code. 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 a bit as a dot time, a Morse code sequence may be made from a combination of the following five bit-strings:

  1. short mark, dot or "dit" (▄▄): 1
  2. longer mark, dash or "dah" (▄▄▄▄▄): 111
  3. intra-character gap (between the dots and dashes within a character): 0
  4. short gap (between letters): 000
  5. medium gap (between words): 0000000

Note that the marks and gaps alternate: dots and dashes are always separated by one of the gaps, and that the gaps are always separated by a dot or a dash.

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 dashes 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.

Cable code

The very long time constants of 19th and early 20th century submarine 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.[45]


Below is an illustration of timing conventions. The phrase "MORSE CODE", in Morse code format, would normally be written something like this, where represents dahs and · represents dits:

−− −−− ·−· ··· ·       −·−· −−− −·· ·
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
M------   O----------   R------   S----   E       C----------   O----------   D------   E

   ^               ^    ^       ^             ^
   |              dah  dit      |             |
symbol space                letter space    word space

Spoken representation

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:

M   O   R   S  E          C    O   D  E
−− −−− ·−· ··· · (space) −·−· −−− −·· ·

is orally:

Dah-dah dah-dah-dah di-dah-dit di-di-dit dit, Dah-di-dah-dit dah-dah-dah dah-di-dit dit.

There is little point in learning to read written Morse as above; rather, the sounds of all of the letters and symbols need to be learned, for both sending and receiving.

Speed in words per minute

All Morse code elements depend on the dot length. A dash is the length of 3 dots, and spacings are specified in number of dot lengths. An unambiguous method of specifying the transmission speed is to specify the dot duration as, for example, 50 milliseconds.

Specifying the dot 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 different dot lengths. It is not immediately clear how a specific word rate determines the dot duration in milliseconds.

Some method to standardize the transformation of a word rate to a dot duration is useful. A simple way to do this is to choose a dot 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 a dot rate that would send the typical word 13 times in exactly one minute.

The typical word thus determines the dot length. It is common to assume that a word is 5 characters long. There are two common typical words: "PARIS" and "CODEX". 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 as "e" and "t". CODEX offers a word rate that is typical of 5-letter code groups (sequences of random letters). Using the word PARIS as a standard, the number of dot units is 50 and a simple calculation shows that the dot length at 20 words per minute is 60 milliseconds. Using the word CODEX with 60 dot units, the dot length at 20 words per minute is 50 milliseconds.

Because Morse code is usually sent by hand, it is unlikely that an operator could be that precise with the dot 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.[46] The Commission 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.[47] The word per minute rate would be close to the PARIS standard, and the code groups per minute would be close to the CODEX 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.[48]

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.[26]

Based upon a 50 dot duration standard word such as PARIS, the time for one dot duration or one unit can be computed by the formula:

T = 1200 / W

Where: T is the unit time, or dot duration in milliseconds, and W is the speed in wpm.

High-speed telegraphy contests are held; according to the Guinness Book of Records in June 2005 at the International Amateur Radio Union's 6th World Championship in High Speed Telegraphy in Primorsko, Bulgaria, Andrei Bindasov of Belarus transmitted 230 morse code marks of mixed text in one minute.[49]

Farnsworth speed

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 of learning Morse code.

Alternative display of common characters in International Morse code

Some methods of teaching Morse code use a dichotomic search table.

Morse code tree3
Graphical representation of the dichotomic search table. The graph branches left for each dot and right for each dash until the character representation is exhausted.

Link budget issues

Morse Code cannot be treated as a classical radioteletype (RTTY) signal when it comes to calculating a link margin or a link budget for the simple reason of it possessing variable length dots and dashes as well as variant timing between letters and words. For the purposes of Information Theory and Channel Coding comparisons, the word PARIS is used to determine Morse Code's properties because it has an even number of dots and dashes.

Morse Code, when transmitted essentially, creates an AM signal (even in on/off keying mode), assumptions about signal can be made with respect to similarly timed RTTY signalling. Because Morse code transmissions employ an on-off keyed radio signal, it requires less complex transmission equipment than other forms of radio communication.

Morse code also requires less signal bandwidth than voice communication, typically 100–150 Hz, compared to the roughly 2400 Hz used by single-sideband voice, although at a lower data rate.

Morse code is usually heard at the receiver as a medium-pitched on/off audio tone (600–1000 Hz), 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 transmitted power is concentrated into a limited bandwidth so narrow receiver filters can be used to suppress interference from adjacent frequencies. The audio tone is usually created by use of a beat frequency oscillator.

The narrow signal bandwidth also takes advantage of the natural aural selectivity of the human brain, further enhancing weak signal readability. This efficiency makes CW extremely useful for DX (distance) transmissions, as well as for low-power transmissions (commonly called "QRP operation", from the Q-code for "reduce power").

The ARRL has a readability standard for robot encoders called ARRL Farnsworth Spacing[50] that is supposed to have higher readability for both robot and human decoders. Some programs like WinMorse[51] have implemented the standard.

Learning methods

People learning Morse code using the Farnsworth method are taught to send and receive letters and other symbols at their full target speed, that is with normal relative timing of the dots, dashes, and spaces within each symbol for that speed. The Farnsworth method is named for Donald R. "Russ" Farnsworth, also known by his call 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 the Koch method, named after German psychologist Ludwig Koch, 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 by W1AW, the American Radio Relay League's headquarters station.


Morse Code Mnemonic chart from Girl Guides handbook 1916
Scout movement founder Baden-Powell's mnemonic chart from 1918

Visual mnemonic charts have been devised over the ages. Baden-Powell included one in the Girl Guides handbook[52] 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 is dah-dah-di-dah, which can be memorized by the phrase "God save the Queen", and the Morse for "F" is di-di-dah-dit, which can be memorized as "Did she like it."

A well-known Morse code rhythm from the Second World War period derives from Beethoven's Fifth Symphony, the opening phrase of which was regularly played at the beginning of BBC broadcasts. The timing of the notes corresponds to the Morse for "V", di-di-di-dah, understood as "V for Victory" (as well as the Roman numeral for the number five).[53][54]

Letters, numbers, punctuation, prosigns for Morse code and non-English variants

Category Character Code
Letters A, a
Letters B, b
Letters C, c
Letters D, d
Letters E, e
Letters F, f
Letters G, g
Letters H, h
Letters I, i
Letters J, j
Letters K, k

Prosign for "Invitation to transmit"
Letters L, l
Letters M, m
Letters N, n
Letters O, o
Letters P, p
Letters Q, q
Letters R, r
Letters S, s
Letters T, t
Letters U, u
Letters V, v
Letters W, w
Letters X, x
Letters Y, y
Letters Z, z
Numbers 0
Numbers 1
Numbers 2
Numbers 3
Numbers 4
Numbers 5
Numbers 6
Numbers 7
Numbers 8
Numbers 9
Punctuation Period [.]
Punctuation Comma [,]
Punctuation Question Mark [?]
Punctuation Apostrophe [']
Punctuation Exclamation Point [!]

KW digraph
Not in ITU-R recommendation
Punctuation Slash/Fraction Bar [/]
Punctuation Parenthesis (Open)
Punctuation Parenthesis (Close)
Punctuation Ampersand (or "Wait") [&]

AS digraph
Prosign for "WAIT"
Punctuation Colon [:]
Punctuation Semicolon [;]

Not in ITU-R ITU-R M.1172 or ITU-R M.1677-1
Punctuation Double Dash [=]
Punctuation Plus sign [+]
Punctuation Hyphen, Minus Sign [-]
Punctuation Underscore [_]

Not in ITU-R ITU-R M.1172 or ITU-R M.1677-1
Punctuation Quotation mark ["]
Punctuation Dollar sign [$]

SX digraph
Not in ITU-R ITU-R M.1172 or ITU-R M.1677-1
Punctuation At Sign [@]

AC digraph
Prosigns End of work
Prosigns Error
Prosigns Invitation to Transmit

Also used for K
Prosigns Starting Signal
Prosigns New Page Signal

AR digraph
Message separator
Single-line display may use printed "+"
Prosigns Understood

Also used for Ŝ
Prosigns Wait

also used for Ampersand [&]
Non-English extensions À, à

Shared by À, Å
Non-English extensions Ä, ä

Shared by Ä, Æ, Ą
Non-English Extensions Å, å

Shared by À, Å
Non-English extensions Ą, ą

Shared by Ä, Æ, Ą
Non-English extensions Æ, æ

Shared by Ä, Æ, Ą
Non-English extensions Ć, ć

Shared by Ć, Ĉ, Ç
Non-English extensions Ĉ, ĉ

Shared by Ć, Ĉ, Ç
Non-English Extensions Ç, ç

Shared by Ć, Ĉ, Ç
Non-English extensions CH, ch

Shared by CH, Ĥ, Š
Non-English extensions Đ, đ

Shared by Đ, É, Ę
Not to be confused with Eth (Ð, ð)
(É is the only accented character included in ITU-R recommendation)
Non-English extensions Ð, ð

Not to be confused with D with stroke (Đ, đ)
Non-English extensions É, é

Shared by Đ, É, Ę
(É is the only accented character included in ITU-R recommendation)
Non-English extensions È, è

Shared by È, Ł
Non-English extensions Ę, ę

Shared by Đ, É, Ę
(É is the only accented character included in ITU-R recommendation)
Non-English extensions Ĝ, ĝ
Non-English extensions Ĥ, ĥ

Shared by CH, Ĥ, Š
Non-English extensions Ĵ, ĵ
Non-English extensions Ł, ł

Shared by È, Ł
Non-English extensions Ń, ń

Shared by Ń, Ñ
Non-English extensions Ñ, ñ

Shared by Ń, Ñ
Non-English extensions Ó, ó

Shared by Ó, Ö, Ø
Non-English extensions Ö, ö

Shared by Ó, Ö, Ø
Non-English extensions Ø, ø

Shared by Ó, Ö, Ø
Non-English extensions Ś, ś
Non-English extensions Ŝ, ŝ

Prosign for "Understood"
Non-English extensions Š, š

Shared by CH, Ĥ, Š
Non-English extensions Þ, þ
Non-English extensions Ü, ü

Shared by Ü, Ŭ
Non-English extensions Ŭ, ŭ

Shared by Ü, Ŭ
Non-English extensions Ź, ź
Non-English extensions Ż, ż


Prosigns for Morse code are special (usually) unwritten procedural signals or symbols that are used to indicate changes in communications protocol status or white space text formatting actions.

Symbol representations

The symbols !, $ and & are not defined inside the ITU recommendation on Morse code, but conventions for them exist. The @ symbol was formally added in 2004.

Exclamation mark

There is no standard representation for the exclamation mark (!), although the KW digraph (▄▄▄▄▄▄▄▄▄▄▄▄▄▄) was proposed in the 1980s by the Heathkit Company (a vendor of assembly 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 prefer the older MN digraph (▄▄▄▄▄▄▄▄▄▄▄) carried over from American landline telegraphy code.

Currency symbols
  • The ITU has never codified formal Morse Code representations for currencies as the ISO 4217 Currency Codes are preferred for transmission.
  • The $ sign code was represented in the Phillips Code, a huge collection of abbreviations used on land line telegraphy, as SX.
  • The representation of the & sign given above, often shown as AS, is also the Morse prosign for wait. In addition, the American landline representation of an ampersand was similar to "ES" (▄▄) and hams have carried over this usage as a synonym for "and" (WX HR COLD ES RAINY, "the weather here is cold & rainy").
Keyboard AT @
  • On May 24, 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 AC digraph (▄▄▄▄▄▄▄▄▄▄▄).
  • This sequence was reportedly chosen to represent "A[T] C[OMMERCIAL]" or a letter "a" inside a swirl represented by a "C".[55] The new character facilitates sending email addresses by Morse code and is notable since it is the first official addition to the Morse set of characters since World War I.

Non-Latin extensions

For Chinese, Chinese telegraph code is used to map Chinese characters to four-digit codes and send these digits out using standard Morse code. Korean Morse code uses the SKATS mapping, originally developed to allow Korean to be typed on western typewriters. SKATS maps hangul characters to arbitrary letters of the Latin script and has no relationship to pronunciation in Korean. For Russian and Bulgarian, Russian Morse code is used to map the Cyrillic characters to four-element codes. Many of the characters are encoded the same way (A, O, E, I, T, M, N, R, K, etc.). Bulgarian alphabet contains 30 characters, which exactly match all possible combinations of 1, 2, 3, and 4 dots and dashes. Russian requires 1 extra character, "Ы" which is encoded with 5 elements.

Unusual variants

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 restored by Spring 1916. Only a small percentage of Western Front (North Atlantic and Mediterranean Sea) traffic was in 'dotty' or 'dashy' Morse during the entire war. In popular culture, this is mostly remembered in the book The Codebreakers by Kahn and in the national archives of the UK and Australia (whose SIGINT operators copied most of this Morse variant). Kahn's cited sources come from the popular press and wireless magazines of the time.[56]

Other forms of 'Fractional Morse' or 'Fractionated Morse' have emerged.[57]

Decoding software

Decoding software for Morse code ranges from software-defined wide-band radio receivers coupled to the Reverse Beacon Network,[58] which decodes signals and detects CQ messages on ham bands, to smartphone applications.[59]

See also


  1. ^ a b c d "International Morse code Recommendation ITU-R M.1677-1". International Telecommunication Union. October 2009. Archived from the original on 6 November 2012. Retrieved 23 December 2011.
  2. ^ F. S. Beechey, Electro-Telegraphy, London: E. & F. N. Spon, 1876, p. 71
  3. ^ F. J. Camm, Radio Engineer's Pocket Book, 2nd ed., Chemical Publishing Co., 1941, p. 72
  4. ^ Headquarters, Department of the Army, TM 11-459, International Morse Code (Instructions), Washington, D.C.: U.S.G.P.O., 1968 pp. 7-8
  5. ^ W.H. Preece, J. Sivewright, Telegraphy, London: Longmans, Green and Co., 1891, p. 40
  6. ^ U.S. Army, FM 24-5, Signal Communication, 1939, pp. 83, 101-108, 227
  7. ^ W. L. Everitt, Communication Engineering, 2nd ed. New York: McGraw-Hill, 1937, p. 6
  8. ^ Editors and Engineers, The "Radio" Handbook, Los Angeles: Editors and Engineers, 1942, p. 180
  9. ^ Headquarters, Department of the Army, TM 11-459, International Morse Code (Instructions), Washington, D.C.: U.S.G.P.O., 1968, pp. 6-7
  10. ^ U. S. Navy, Bureau of Naval Personnel, Radioman 3 & 2, Washington, D.C.: U.S.G.P.O., 1957, pp. 105-111
  11. ^ War Department, TM 11-459, Instructions for Learning International Morse Characters, 1943, pp. 52, 68-72
  12. ^ Fahie, John Jacob (1884). A History of Electric Telegraphy, to the Year 1837 (PDF). E. & F.N. Spon. Archived (PDF) from the original on 15 July 2017. Retrieved 21 November 2017.
  13. ^ Burns 2004, p. 79
  14. ^ Burns 2004, p. 84
  15. ^ "Learning Morse Code". Archived from the original on 20 September 2017. Retrieved 1 December 2017.
  16. ^ L. Peter Carron, "Morse Code: The Essential Language", Radio amateur's library, issue 69, American Radio Relay League, 1986 ISBN 0-87259-035-6.
  17. ^ R. J. Eckersley, Amateur radio operating manual, Radio Society of Great Britain, 1985 ISBN 0-900612-69-X.
  18. ^ "Iddy-umpty". Oxford English Dictionary. Retrieved 22 October 2016. (available online to subscribers)
  19. ^ Captain Linwood S. Howeth (1963). History of Communications-Electronics in the United States: Early Navy Efforts to Develop Aircraft Radio Navy.
  20. ^ "K2TQN Vintage Radio Column". Archived from the original on 11 September 2017. Retrieved 1 December 2017.
  21. ^ a b "How the Zeppelin Raiders Are Guided by Radio Signals". Popular Science Monthly. April 1918. pp. 632–634. Retrieved March 4, 2018.
  22. ^ "An obituary for Morse code" Archived 2017-03-30 at the Wayback Machine, The Economist, January 23, 1999.
  23. ^ "Maritime Radio Historical Society". Archived from the original on 25 January 2018. Retrieved 1 December 2017.
  24. ^ "Morse code training in the Air Force". 10 December 2015. Archived from the original on 2 July 2017. Retrieved 1 December 2017.
  25. ^ "Amendments to the International Aeronautical and Maritime Search and Rescue (IAMSAR) Manual" (PDF). Retrieved 1 December 2017.
  26. ^ a b "Radiotelegraph Operator License (T)". Federal Communications Commission. Archived from the original on January 13, 2015. Retrieved January 21, 2015.
  27. ^ "Maritime Radio Historical Society". Archived from the original on 9 October 2017. Retrieved 1 December 2017.
  28. ^ Perera, Tom. "The "Morse" Code and the Continental Code". W1TP Telegraph & Scientific Instruments Museums. Archived from the original on 9 December 2011. Retrieved 23 December 2011.
  29. ^ a b "The Art & Skill of Radio Telegraphy" (PDF). 2002. Archived (PDF) from the original on 2012-02-26. Retrieved 2013-06-14.
  30. ^ "Extremely High Speed Club official web page". Archived from the original on 28 June 2017. Retrieved 1 December 2017.
  31. ^ "Chapter 1. Air Navigation". January 3, 2015. Archived from the original on December 1, 2014. Retrieved January 21, 2015.
  32. ^ COM 3.2, Canadian AIM Archived November 22, 2013, at the Wayback Machine
  33. ^ "WG - WINNIPEG". Archived from the original on 2 December 2017. Retrieved 1 December 2017.
  34. ^ IARUWeb: The International Amateur Radio Union Archived September 6, 2012, at the Wayback Machine
  35. ^ "Italy Joins No-Code Ranks as FCC Revives Morse Debate in the US". The ARRL Letter. 24 (31). August 12, 2005. Archived from the original on November 5, 2011. Retrieved 2012-04-02.
  36. ^ "1998 Biennial Regulatory Review — Amendment of Part 97 of the Commission's Amateur Service Rules" (PDF). Archived from the original (PDF) on October 31, 2005. Retrieved December 4, 2005.
  37. ^ "Aeronautical Information Manual (AIM)". Archived from the original on September 4, 2009. Retrieved 2007-12-10.
  38. ^ "Prosigns". QTH.Com. Archived from the original on September 24, 2015. Retrieved January 21, 2015.
  39. ^ "#FactsOnly: The Most Interesting Things You Didn't Know About Nokia". Complex. Retrieved 2018-05-13.
  40. ^ Nokia files patent for Morse Code-generating cellphone Archived 2017-06-25 at the Wayback Machine, 12 March 2005, Engadget.
  41. ^ "Android Accessibility Help: Use Morse Code". Google. 2018. Retrieved 21-December-2018. Check date values in: |access-date= (help)
  42. ^ Dennis W. Ross, "Morse Code: A Place in the Mind," QST, March, 1992, p. 51.
  43. ^ Ronald J. Curt, "In the Blink of an Eye," QST, July 1990 p. 44.
  44. ^ Donna Burch, "Morse Code from the Heart," QST July 1990 p. 45.
  45. ^ Ken Beauchamp, History of Telegraphy, Institution of Electrical Engineers IET, 2001 ISBN 0852967926 page 150
  46. ^ Title 47 Code of Federal Regulations §13.207(c) and Title 47 Code of Federal Regulations §13.209(d)
  47. ^ 47 CFR §13.203(b)
  48. ^ Title 47 Code of Federal Regulations §97.503, 1996 version
  49. ^ "Fastest speed for a morse code transmission". Archived from the original on 3 July 2017. Retrieved 1 December 2017.
  50. ^ "A Standard for Morse Timing Using the Farnsworth Technique" (PDF). Archived (PDF) from the original on 25 January 2018. Retrieved 1 December 2017.
  51. ^ "Custom Farnsworth Spacing Configuration". Archived from the original on 2016-03-04. Retrieved 2013-11-21.
  52. ^ "Girl Guiding by Lord Baden-Powell" (PDF). Pearson. 1938. Archived (PDF) from the original on 2015-10-06. Retrieved 2015-09-06. Some people find it easier to remember the does [sic] and dashes by picturing them as forming the letters— thus:— (p61)
  53. ^ Glenn Stanley, The Cambridge Companion to Beethoven, p.269, Cambridge University Press, 2000 ISBN 0-521-58934-7.
  54. ^ William Emmett Studwell, The Americana Song Reader, p.62, Routledge, 1997 ISBN 0-7890-0150-0.
  55. ^ "International Morse Code Gets a New ITU Home, New Character". Archived from the original on September 30, 2007. Retrieved February 27, 2007.
  56. ^ Wythoff, Grant (July 2014). "The Invention of Wireless Cryptography". The Appendix: Futures of the Past. 2 (3). Archived from the original on 2014-12-08. Retrieved 2015-01-28.
  57. ^ "Fractionated Morse, and Other Oddities". Retrieved 2013-11-21.
  58. ^ "Welcome! - Reverse Beacon Network". Archived from the original on 12 September 2017. Retrieved 1 December 2017.
  59. ^ "Morse Decoder Test – iPhone / iPad | Gerolf Ziegenhain". 2013-05-20. Archived from the original on 2017-07-27. Retrieved 2016-09-17.


  • Burns, R. W. (2004), Communications: an international history of the formative years, Institution of Electrical Engineers, ISBN 0-86341-327-7

External links

Alfred Vail

Alfred Lewis Vail (September 25, 1807 – January 18, 1859) was an American machinist and inventor. Along with Samuel Morse, Vail was central in developing and commercializing American telegraphy between 1837 and 1844.Vail and Morse were the first two telegraph operators on Morse's first experimental line between Washington, DC, and Baltimore, and Vail took charge of building and managing several early telegraph lines between 1845 and 1848. He was also responsible for several technical innovations of Morse's system, particularly the sending key and improved recording registers and relay magnets. Vail left the telegraph industry in 1848 because he believed that the managers of Morse's lines did not fully value his contributions.

His last assignment, superintendent of the Washington and New Orleans Telegraph Company, paid him only $900 a year, leading Vail to write to Morse, "I have made up my mind to leave the Telegraph to take care of itself, since it cannot take care of me. I shall, in a few months, leave Washington for New Jersey, ... and bid adieu to the subject of the Telegraph for some more profitable business."

American Morse code

American Morse Code — also known as Railroad Morse—is the latter-day name for the original version of the Morse Code developed in the mid-1840s, by Samuel Morse and Alfred Vail for their electric telegraph. The "American" qualifier was added because, after most of the rest of the world adopted "International Morse Code," the companies that continued to use the original Morse Code were mainly located in the United States. American Morse is now nearly extinct—it is most frequently seen in American railroad museums and American Civil War reenactments—and "Morse Code" today virtually always means the International Morse which supplanted American Morse.


CQD (transmitted in Morse code as ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄) is one of the first distress signals adopted for radio use. It was announced on 7 January 1904, by "Circular 57" of the Marconi International Marine Communication Company, and became effective beginning 1 February 1904 for Marconi installations.

Land telegraphs had traditionally used "CQ" ("sécu", from the French word sécurité) to identify alert or precautionary messages of interest to all stations along a telegraph line, and CQ had also been adopted as a "general call" for maritime radio use. However, in landline usage there was no general emergency signal, so the Marconi company added a "D" ("distress") to CQ in order to create its distress call. Sending "D" was already used internationally to indicate an urgent message. Thus, "CQD" is understood by wireless operators to mean, "All stations: distress." Contrary to popular belief, CQD does not stand for "Come Quick, Danger", "Come Quickly: Distress", "Come Quick – Drowning!", or "C Q Danger" ("Seek You, Danger"); these are backronyms.Although used worldwide by Marconi operators, CQD was never adopted as an international standard, since it could be mistaken for a general call "CQ" if the reception were poor. At the second International Radiotelegraphic Convention, held in Berlin in 1906, Germany's Notzeichen distress signal of three-dots/three-dashes/three-dots (▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄) was adopted as the international Morse code distress signal. (This distress signal soon became known as "SOS" because if gaps are inserted it can be thought of as the Morse codes for those letters – by contrast CQD is transmitted as three distinct letters with a short gap between each. Germany had first adopted this distress signal in regulations effective 1 April 1905.)Between 1899 and 1908, nine documented rescues were made by the use of wireless. The earliest of these was a distress call from the East Goodwin lightship. However, for the earliest of these, there was no standardized distress signal. The first US ship to send a wireless distress call in 1905 simply sent HELP (in both International Morse and American Morse). By February 1904, the Marconi Wireless Company required all its operators to use CQD for a ship in distress or for requiring URGENT assistance. In the early morning of 23 January 1909, whilst sailing into New York from Liverpool, RMS Republic collided with the Italian liner SS Florida in fog off the island of Nantucket, Massachusetts, United States. Radio Operator Jack Binns sent the CQD distress signal by wireless transmission.

On April 15, 1912, RMS Titanic radio operator Jack Phillips initially sent "CQD", which was still commonly used by British ships. Harold Bride, the junior radio operator, suggested using "SOS", saying half-jokingly that it might be his last chance to use the new code. Phillips thereafter began to alternate between the two. Though Bride survived the sinking, Phillips did not.

Continuous wave

A continuous wave or continuous waveform (CW) is an electromagnetic wave of constant amplitude and frequency, almost always a sine wave, that for mathematical analysis is considered to be of infinite duration. Continuous wave is also the name given to an early method of radio transmission, in which a sinusoidal carrier wave is switched on and off. Information is carried in the varying duration of the on and off periods of the signal, for example by Morse code in early radio. In early wireless telegraphy radio transmission, CW waves were also known as "undamped waves", to distinguish this method from damped wave signals produced by earlier spark gap type transmitters.

Hagal dune field

Hagal is the informal name of a dune field on Mars located below the north pole of Mars. Its name derives from the sand dunes in Frank Herbert's novel Dune and the fictional planet Hagal. It is located at coordinates 78.0° N latitude, 84.0° E longitude, and consists of linear and round dunes with a southeast slipface orientation. It was one of the dune formations targeted for imaging by the HiRISE camera, onboard the Mars Reconnaissance Orbiter, at the rate of one image every six weeks. in the third year (MY31–Mars Year 31) of its seasonal expedition. It is also known as the "Martian Morse Code" due to the linear and rounded formations of its dunes, which have the appearance of dots and dashes.

Light characteristic

A light characteristic is a graphic and text description of a navigational light sequence or colour displayed on a nautical chart or in a Light List with the chart symbol for a lighthouse, lightvessel, buoy or sea mark with a light on it. The graphic indicates how the real light may be identified when looking at its actual light output type or sequence. Different lights use different colours, frequencies and light patterns, so mariners can identify which light they are seeing.

Morse Code (horse)

Morse Code (foaled 1929) was a British Thoroughbred racehorse who won the 1938 Cheltenham Gold Cup. His Gold Cup victory was achieved at the expense of Golden Miller, who was attempting to win the race for the sixth time. He had previously won the Grand Annual Chase and went on to finish second when odds-on favourite for the Gold Cup in 1939.

Morse code abbreviations

Morse code abbreviations are used to speed up Morse communications by foreshortening textual words and phrases. Morse abbreviations are short forms representing normal textual words and phrases formed from some (fewer) characters borrowed from the words or phrases being abbreviated. Aside: Morse code abbreviations are not the same as prosigns. Morse abbreviations are composed of (normal) textual alpha-numeric character symbols with normal Morse code inter-character spacing; the character symbols in abbreviations, unlike the delineated character groups representing Morse code prosigns, are not "run together" or concatenated in the way most prosigns are formed.

From 1845 until well into the second half of the 20th century, commercial telegraphic code books were used to shorten telegrams, e.g. "Pascoela = Natives have plundered everything from the wreck". However, these are distinct from abbreviations.

The following Table of Morse code abbreviations and further references to Brevity codes such as 92 Code, Q code, Z code and R-S-T system serve to facilitate fast and efficient Morse code communications.

Morse code for non-Latin alphabets

This is a summary of the use of Morse code to represent alphabets other than Latin.

On-off keying

On-off keying (OOK) denotes the simplest form of amplitude-shift keying (ASK) modulation that represents digital data at the presence or absence of a carrier wave. In its simplest form, the presence of a carrier for a specific duration represents a binary one, while its absence for the same duration represents a binary zero. Some more sophisticated schemes vary these durations to convey additional information. It is analogous to unipolar encoding line code.

On-off keying is most commonly used to transmit Morse code over radio frequencies (referred to as CW (continuous wave) operation), although in principle any digital encoding scheme may be used. OOK has been used in the ISM bands to transfer data between computers, for example.

OOK is more spectrally efficient than frequency-shift keying, but more sensitive to noise when using a regenerative receiver or a poorly implemented superheterodyne receiver.

For a given data rate, the bandwidth of a BPSK (Binary Phase Shift keying) signal and the bandwidth of OOK signal are equal.

In addition to RF carrier waves, OOK is also used in optical communication systems (e.g. IrDA).

In aviation, some possibly unmanned airports have equipment that let pilots key their VHF radio a number of times in order to request an Automatic Terminal Information Service broadcast, or turn on runway lights.

Prosigns for Morse code

Procedure signs or prosigns are shorthand signals used in radio telegraphy procedures, for the purpose of simplifying and standardizing communications related to radio operating issues among two or more radio operators. They are distinct from general Morse code abbreviations, which consist mainly of brevity codes that convey messages to other parties with greater speed and accuracy.

There are also specialized variations used in radio nets to manage transmission and formatting of messages. In this usage, Morse prosigns play a role similar to the role played by the nonprinting control characters of teleprinter and computer character set codes such as Baudot or ASCII.

The development of prosigns began in the 1860s for wired telegraphy. They are distinguished from common Morse abbreviations. Since Morse code communication preceded voice communications by several decades, many of the much older Morse prosigns have exact equivalent procedure words for use in the more recent radio telephony (voice).

Prosigns may be represented in printed material either by a sequence of dots and dashes, or by a sequence of letters, which, if sent without the normal inter-character spacing (concatenated), correspond to the prosign symbol.

Russian Morse code

The Russian Morse code approximates the Morse code for the Latin alphabet. It was enacted by the Russian government in 1856.To memorize the codes, practitioners utilize mnemonics known as напевы (loosely translated "melodies" or "chants"). The "melody" corresponding to a character is a sung phrase: syllables containing the vowels а, о, and ы correspond to dashes and are sung long, while syllables containing other vowels, as well the syllable ай, correspond to dots and are sung short. The specific "melodies" employed differ among various schools.The correspondences between Cyrillic and Latin letters were codified in MTK-2, KOI-7, and KOI-8.


SOS is the International Morse code distress signal (▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄); the overscore indicates that the normal gaps between the letters should be omitted. It is used as a start-of-message mark for transmissions requesting help when loss of life or catastrophic loss of property is imminent. Other prefixes are assigned for mechanical breakdowns, requests for medical assistance, and a relayed distress signal originally sent by another station.

This distress signal was first adopted by the German government radio regulations effective 1 April 1905, and became the worldwide standard under the second International Radiotelegraphic Convention, which was signed on 3 November 1906, and became effective on 1 July 1908. SOS remained the maritime radio distress signal until 1999, when it was replaced by the Global Maritime Distress and Safety System. SOS is still recognized as a standard distress signal that may be used with any signaling method.The SOS distress signal is a continuous sequence of three dots, three dashes, and three dots, with no spaces between the letters (notated by the overscore). In International Morse Code, three dots form the letter S, and three dashes make the letter O, so "S O S" became a way to remember the order of the dots and dashes. In modern terminology, SOS is a Morse "procedural signal" or "prosign", and the formal way to write it is with a bar above the letters or enclosed in angle brackets: SOS or .

Even though SOS does not stand for anything, in popular usage it became associated with such phrases as "Save Our Souls" and "Save Our Ship". SOS is only one of several ways that the combination could have been written; for example, IWB, VZE, 3B, or V7 all produce exactly the same sound; SOS is just the easiest to remember.

Signal lamp

A signal lamp (sometimes called an Aldis lamp, after Arthur Cyril Webb Aldis, who invented a widely used design, or a Morse lamp) is a visual signaling device for optical communication, typically using Morse code. Modern signal lamps are focused lamps which can produce a pulse of light. In large versions, this pulse is achieved by opening and closing shutters mounted in front of the lamp, either via a manually operated pressure switch, or, in later versions, automatically. With hand held lamps, a concave mirror is tilted by a trigger to focus the light into pulses. The lamps were usually equipped with some form of optical sight, and were most commonly used on naval vessels and in airport control towers (using color signals for stop or clearance). In manual signaling, a signalman would aim the light at the recipient ship and turn a lever, opening and closing the shutter over the lamp, to emit flashes of light to spell out text messages in Morse code. QOn the recipient ship, a signalman would observe the blinking light, often with binoculars, and translating the code into text.

Telegraph code

A telegraph code is one of the character encodings used to transmit information through telegraphy machines. The most famous such code is Morse code.


A telegraphist (British English), telegrapher (American English), or telegraph operator is an operator who uses a telegraph key to send and receive the Morse code in order to communicate by land lines or radio.

Telegraphist was one of the very first "high-technology" professions of the modern era. Many young men and young women left their farms and fishing communities in the late 19th century to take high-paying jobs as professional telegraph operators. In those early days telegraphers were in such demand that operators could move from place to place and job to job to achieve ever-higher salaries, thereby freeing them from subsistence lives on family farms.

During the Great War the Royal Navy enlisted many volunteers as radio telegraphists. Telegraphists were indispensable at sea in the early days of wireless telegraphy, and many young men were called to sea as professional radiotelegraph operators who were always accorded high-paying officer status at sea. Subsequent to the Titanic disaster and the Radio Act of 1912, the International Safety of Life at Sea (SOLAS) conventions established the 500kHz maritime distress frequency monitoring and mandated that all passenger-carrying ships carry licensed radio telegraph operators.High-paying jobs as seagoing ship's radiotelegraphy officers were still common until the late 20th century. In the 21st century, the employment of professional radio telegraphers was largely discontinued in maritime service and replaced by the use of satellite communications services.

The use of Morse code is over a century old. Fluent Morse code telegraphers still enjoy sending Morse code using manually operated mechanical keys or electronic keyers. Although Morse code is no longer used in commercial practices, the use of hand-sent Morse code seems to be growing among amateur radio operators, even though Morse proficiency is no longer required to obtain an amateur radio licence.

Using the computer keyboard or hand-operated telegraph key, today almost all Morse code operators are amateur radio enthusiasts.

Wabun code

The Wabun code (和文モールス符号, wabun mōrusu fugō, Japanese text in Morse code) is a form of Morse code used to send Japanese text. Unlike International Morse Code, which represents letters of the Latin script, in Wabun each symbol represents a Japanese kana. For this reason, Wabun code is also sometimes called Kana code.

When Wabun Code is intermixed with International Morse code, the prosign DO (▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄) is used to announce the beginning of Wabun, and the prosign SN (▄▄▄▄▄▄▄▄▄▄▄▄▄▄) is used to return to International Code.

Wireless telegraphy

Wireless telegraphy means transmission of telegraph signals by radio waves; a more specific term for this is radiotelegraphy. Before about 1910 when radio became dominant, the term wireless telegraphy was also used for various other experimental technologies for transmitting telegraph signals without wires, such as electromagnetic induction, and ground conduction telegraph systems.Radiotelegraphy was the first means of radio communication; the first practical radio transmitters and receivers invented in 1894-5 by Guglielmo Marconi used radiotelegraphy. It continued to be the only type of radio transmission during the first three decades of radio, called the "wireless telegraphy era" up until World War I, when the development of amplitude modulation (AM) radiotelephony allowed sound (audio) to be transmitted by radio. In radiotelegraphy, information is transmitted by pulses of radio waves of two different lengths called "dots" and "dashes", which spell out text messages, usually in Morse code. In a manual system, the sending operator taps on a switch called a telegraph key which turns the transmitter on and off, producing the pulses of radio waves. At the receiver the pulses are audible in the receiver's speaker as beeps, which are translated back to text by an operator who knows Morse code.

Radiotelegraphy was used for long distance person-to-person commercial, diplomatic, and military text communication throughout the first half of the 20th century. It became a strategically important capability during the two world wars, since a nation without long distance radiotelegraph stations could be isolated from the rest of the world by an enemy cutting its submarine telegraph cables. Beginning about 1908, powerful transoceanic radiotelegraphy stations transmitted commercial telegram traffic between countries at rates up to 200 words per minute. Radiotelegraphy was transmitted by several different modulation methods during its history. The primitive spark gap transmitters used until 1920 transmitted damped waves, which had very large bandwidth and tended to interfere with other transmissions. This type of emission was banned by 1930. The vacuum tube (valve) transmitters which came into use after 1920 transmitted code by pulses of unmodulated sinusoidal carrier wave called continuous waves (CW), which is still used today. To make CW transmissions audible, the receiver requires a circuit called a beat frequency oscillator (BFO). A third type of modulation, frequency shift keying (FSK) was used mainly by radioteletypes. Morse code radiotelegraphy was gradually replaced by radioteletype networks (RTTY) in most high volume applications by World War 2. Today it is nearly obsolete, the only remaining users are the radio amateur community and some limited training by the military for emergency use.

Words per minute

Words per minute, commonly abbreviated wpm (sometimes uppercased WPM), is a measure of words processed in a minute, often used as a measurement of the speed of typing, reading or Morse code sending and receiving.

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