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Morse Code

One of the 100 Greatest Inventions

Morse code is a system of representing letters, numbers and punctuation marks by means of a code signal sent intermittently. It was developed by Samuel Morse and Alfred Vail in 1835.

Morse code is an early form of digital communication. It uses two states (on and off) composed into five symbols: dit (·), dah (–), short gap (between letters), medium gap (between words) and long gap (between sentences). Both the view as five symbols and the view as a binary code (with two states) are correct.

History of Morse code

Morse became interested in telegraphy in 1832, and worked out the basics of a relay system in 1835. The equipment was gradually improved and was demonstrated in 1837. Morse developed "lightning wires" and "Morse code", and applied for a patent in 1840. A line was constructed between Baltimore, Maryland, and Washington, DC, and the first message, sent on May 24, 1844, was "What hath God wrought!"

Morse's original code consisted of combinations of dits and dahs that represented numbers. Each number represented a word. This required looking up the number in a book to find the word it represented. A telegraph key was then used to tap out the sequence of dits, dahs, and pauses that represented the number.

Although Morse invented the telegraph, he lacked technical expertise. He entered an agreement with Alfred Vail who built more practical equipment. Vail developed a system in which each letter or symbol is sent individually, using combinations of dits, dahs, and pauses. Morse and Vail agreed that Vail's method of representing individual symbols would be included in Morse's patent. This system, known as American Morse code, was the version that was used to transmit the first telegraph message.

The code may be transmitted as an audio tone, a steady radio signal switched on and off (only the carrier wave, or CW, also continuous wave), an electrical pulse down a telegraph wire, or as a mechanical or visual signal (e.g. a flashing light).

In general, any code representing written symbols as variable length signals can be called a Morse code, but the term is used specifically for the two kinds of Morse code used for the English alphabet and associated symbols. American Morse Code was used in the wired telegraph systems that made up the first long-distance electronic communication system. International Morse Code, which uses only dits and dahs (eliminating the pause), is used today.

Telegraph companies charged based on the length of the message sent. Elaborate commercial codes were developed that encoded common phrases in five-letter groups that were sent as single words. Examples: BYOXO ("Are you trying to crawl out of it?"), LIOUY ("Why do you not answer my question?"), and AYYLU ("Not clearly coded, repeat more clearly."). The letters of these five-letter code words were sent individually using Morse code. In computer networking terminology we would say the commercial code is layered on top of Morse code, which in turn is layered on top of binary code, which in turn is layered on top of a physical telegraph wire. Still in use in Amateur Radio are the Q code and Z code; they were and are used by the operators themselves for service information like link quality, frequency changes, and telegram numbering.

On January 8, 1838 Alfred Vail demonstrated a telegraph code using dits and dahs which was the forerunner of Morse code.

When considered as a standard for information encoding, Morse code had a successful lifespan that has not yet been surpassed by any other electronic encoding scheme. Morse code was used as an international standard for maritime communication until 1999 when it was replaced by the Global Maritime Distress Safety System. When the French navy ceased using Morse code in 1997, the final message transmitted was "Calling all. This is our last cry before our eternal silence." See also: international distress frequency

Recently a few widely publicized speed contests have been held between expert Morse code operators and expert cellphone SMS text messaging users (see external links). Morse code has consistently won the contests, leading to speculation that cellphone manufacturers may eventually build a Morse code interface into cellphones. The interface would automatically translate the Morse code input into text so that it could be sent to any SMS capable cellphone so therefore the receiver of the message need not know Morse code to read it. Other speculated applications include taking an existing assistive application of Morse code and using the vibrating alert feature on the cellphone to translate SMS messages to Morse code for silent, hands free "reading" of the incoming messages. Several cellphones already have informative audible Morse code ring tones and alert messages, for example: many Nokia cellphones have an option to beep SMS in Morse code when it receives an SMS text message. These kinds of innovations could lead to a Morse code revival. There are third party applications already available for some cellphones that allow Morse code input for sending SMS (see external links).

American Morse Code

Virtually extinct, and no longer in commercial use, American Morse Code, sometimes referred to as "Railroad Morse" uses a slightly different structure of dits and dahs and uniquely spaces also to represent numbers, letters, and special characters. This style of Morse code was developed for land operators working over telegraph wire rather than via radio signals. It is most frequently seen today in railroad museums and American civil war re-enactments.

This older style of code was developed to accommodate the way in which operators listened to Morse code sent to them. Rather than hearing tones from a speaker or headphones as we do now using International Morse Code, in these earliest days of telegraphy one would hear two clicks from a mechanical sounding device for each key movement. Pressing the key makes a click, and releasing the key makes a clack. Thus, each key movement, up or down was uniquely heard. In this mechanical sounder system, an "A" (·–) would sound like: clickClack click - - - Clack. This is quite different from CW code where beeps are heard for as long as the key is engaged.

Most often land line telegraph operators worked for a railroad or later for Western Union and news reporting services. Thomas Alva Edison was such an operator in his teenage years, as were countless youths of his time.

Modern International Morse Code

The Modern International Morse Code was invented by Friedrich Clemens Gerke in 1848 and used for the telegraphy between Hamburg and Cuxhaven in Germany. After some minor changes in 1865 it has been standardised at the International Telegraphy congress in Paris (1865), and later normed by the ITU as International Morse Code.

International Morse code is still in use today, although it has become almost exclusively the province of amateur radio operators. Until 2003 the International Telecommunications Union (ITU) mandated Morse code proficiency as part of the amateur radio licensing procedure throughout the world. In some countries, certain parts of the amateur radio bands are still reserved for transmission of Morse code signals only.

Since Morse relies on only an (on-off keyed) radio signal, it requires less complex equipment than other forms of radio communication, and it can be used in very high noise / low signal environments. It also requires less bandwidth than voice communications, typically 100-150 Hz, compared to the roughly 4000 Hz of single-sideband voice. The extensive use of pro-signs, Q codes, and restricted format of typical messages facilitates communication between amateur radio operators who do not share a common mother tongue and would have great difficulty in communicating using voice modes.

Morse code is also very popular among QRP operators for enabling very long distance, low-power communication. Readability can be sustained by trained operators even though the signal is only faintly readable. This level of "penetration" is due to the fact that all transmitted energy is concentrated in a very small bandwidth making the use of a narrow receiver bandwidth practical. A narrow bandwidth receiver uses filters to exclude interference on frequencies close to the desired frequency. Concentrating the transmitted energy in a small bandwidth gives the signal a "spectral brightness" that is much higher than the average natural noise (but see also spread spectrum).

In the United States until 1991, a demonstration of the ability to send and receive Morse code at 5 words per minute (WPM) was required to receive an FCC amateur radio license. Demonstration of this ability is still required for the privilege to use the HF bands. Until 1999, proficiency at the 20 WPM level was required to receive the highest level of amateur license (Extra Class); effective April 15, 2000, the FCC reduced the Extra Class requirement to 5 WPM.[1] (http://www.arrl.org/announce/regulatory/wt98-143ro.pdf)

The World Radiocommunication Conference of 2003 (WRC-03) made optional the international Morse code requirement for amateur radio licensing. Although the requirement remains on the books in the US, Canada, and elsewhere, some countries are working to eliminate the requirement entirely.

Amateur and military radio operators skilled in Morse code can often understand ("copy") code in their heads at rates in excess of 40 WPM. Although the traditional telegraph key (straight key)is still used by many amateurs, the use of semi- and fully-automatic electronic keyers (known as "bugs") is prevalent today. Computer software is also frequently employed to produce and decode Morse code RF signals.

As of 2004 commercial radiotelegraph licenses are still being issued in the United States by the Federal Communications Commission. Designed for shipboard and coast station operators, they are awarded to applicants who pass written examinations on advanced radio theory and show 20 WPM code proficiency (this requirement is waived for "old" Extra Class licensees). However, since 1999 the use of satellite and very high frequency maritime communications systems (GMDSS) have essentially made them obsolete.

On May 24, 2004, the 160th anniversary of the first telegraphic transmission, the ITU added the "@" (the "commercial at" or "commat") character to the Morse character set and is the digraph "AC" (probably to represent "A[T] C[OMMERCIAL]" or the letter "a" inside the swirl appearing to be a "C").[2] (http://www.cjonline.com/stories/021704/pag_morsecode.shtml) The new character facilitates sending electronic mail addresses by Morse code and is notable since it is the first official addition to the Morse set of characters since World War I.

Morse code as an assistive technology

Morse code has a 21st century role as an assistive technology, helping people with a variety of disabilities to communicate. Morse can be sent by someone with severe motion disability, as long as they have some minimal motor control. In some cases this means alternately blowing into and sucking on a plastic tube ("puff and sip" interface). People with severe sensory disabilities (e.g. deaf and blind) can receive Morse through a skin buzzer. Products are available that allow a computer operating system to be controlled by Morse code, allowing the user access to the Internet and electronic mail. See: Morse2000 assistive communications site (http://www.uwec.edu/ce/Morse2000.htm)

Representation and timing

There are two "symbols" used to represent letters, called dots and dashes or (more commonly among CW users) dits and dahs. The length of the dit determines the speed at which the message is sent, and is used as the timing reference. Here is an illustration of the timing conventions. Its intent is to show exact timing – it would normally be written something like this:

--- ·-· ··· · / -·-· --- -·· · M O R S E (space) C O D E
where - represents dah and · represents dit. Here's the exact conventional timing for the same message (= represents signal on, . represents signal off, each for the length of a dit):

^ ^ ^ ^ ^ | dah dit | word space symbol space letter space
In text-book, full-speed Morse, a dah is conventionally 3 times as long as a dit. Spacing between dits and dahs in a character is the length of one dit. Spacing between letters in a word is the length of a dah (3 dits). Spacing between words is 7 dits.

Those learning Morse are often taught to send and understand 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. Exaggerated spaces between symbols and words are used to give 'thinking time', which can be reduced with practice and familiarity. This makes the sound 'shape' of the letters and symbols easier to learn. This teaching method is referred to as the Farnsworth method.

Morse code is often spoken or written as follows:

--- ·-· ··· · / -·-· --- -·· ·
Dah-dah dah-dah-dah di-dah-dit di-di-dit dit, Dah-di-dah-dit dah-dah-dah dah-di-dit dit.

Note that 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, both to send and to receive.

The speed of Morse code is typically specified in "words per minute" (WPM). The Paris standard defines the speed of Morse transmission as the dot and dash timing needed to send the word "Paris" a given number of times per minute. The word Paris is chosen because it is precisely 50 "dits" based on the text book timing.

It has been claimed that musicians learn the rhythms of the Morse code characters faster than non-musicians. Conversely, Morse code has been used in music, both as a source for rhythmic patterns and as recorded samples, such as Vladimir Ussachevsky's Wireless Fantasy.

Letters, numbers, punctuation, prosigns

Letter International
Letter International
A · - · - N - · - ·
B - · · · - · · · O - - - . _ .
C - · - · · · _ · P · - - · · · · · ·
D - · · - · · Q - - · - · · - ·
E · · R · - · · _ · ·
F · · - · · - · S · · · · · ·
G - - · - - · T - -
H · · · · · · · · U · · - · · -
I · · · · V · · · - · · · -
J · - - - · - · - W · - - · - -
K - · - - · - X - · · - · - · ·
L · - · · Y - · - - · · _ · ·
M - - - - Z - - · · · · · _ ·

Letters, numbers, punctuation, prosigns

(† "_" signifies a "space" which is part of the character. L is a long "dash".)


International code American Morse
0 -----
1 ·---- ·--·
2 ··--- ··-··
3 ···-- ···-·
4 ····- ····-
5 ····· ---
6 -···· ······
7 --··· --··
8 ---·· -····
9 ----· -··-

(† 0 is a "dash" longer than that of an L.)

The "@" symbol was added in 2004, and combines A and C into one character.

Special symbols (prosigns)

Prosigns or procedural signals are dot/dash sequences that have a special meaning. They can often be viewed as if they were composed of one, two or three Morse code alphabetic characters. When composed in this way of more than one character, they are sent "run together"; that is, omitting the normal pauses that would occur if they were being sent as letters of text. These ligatures are normally represented in print by the letters with a ligating bar above them.

Sign Code Meaning Comment
\overline{\mbox{AR}} ·-·-· Stop (end of message) Often written +
\overline{\mbox{AS}} ·-··· Wait (for 10 seconds) Respond with C (yes). AS2 means wait 2 min, AS5 5 min, etc. For pauses of 10 min or longer, use QRX
\overline{\mbox{BT}} -···- Separator within message Often written =.
\overline{\mbox{CL}} -·-··-·· Going off the air "Clear"
\overline{\mbox{K}} -·- General invitation to transmit Often sent after CQ
\overline{\mbox{KN}} -·--· Specific invitation to transmit Often indicates "back-to-you"
\overline{\mbox{R}} ·-· Received and understood "Roger"
\overline{\mbox{SK}} ···-·- End (end of contact) In practice
\overline{\mbox{SOS}} ···---··· Serious distress message and request for urgent assistance Not to be used unless there is imminent danger to life or to a vessel at sea. See SOS

Although these are not really prosigns, an error may be indicated by some series.

······· Error, correct word follows (six or more dots in a row)
· · · Error (easily identifiable by "broken" rhythm)



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