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Morse code

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Chart of the Morse code letters and numerals
Chart of the Morse code letters and numerals

Morse code is a type of character encoding that transmits telegraphic information using rhythm. Morse code uses a standardized sequence of short and long elements to represent the letters, numerals, punctuation and special characters of a given message. The short and long elements can be formed by sounds, marks, or pulses, in on-off keying and are commonly known as "dots" and "dashes" or "dits" and "dahs". The speed of Morse code is measured in words per minute (WPM) or characters per minute.

Contents

History and Applications

Morse code was originally created for Samuel F. B. Morse's electric telegraph in the early 1840s. What is called Morse code today is actually somewhat different from what was originally developed. The Modern International Morse code, or continental code, was created by Friedrich Clemens Gerke in 1848, was standardised at the International Telegraphy congress in Paris (1865), and was later made the norm by the International Telecommunication Union (ITU) as International Morse code.

Morse code was extensively used for early radio communication beginning in the 1890s. In the early part of the twentieth century, the majority of high-speed international communication was conducted in Morse code, using telegraph lines, undersea cables, and radio circuits. However, the variable length of the Morse characters made it hard to adapt to automated circuits, so for most electronic communication it has been replaced by machine readable formats, such as Baudot code and ASCII.

The most popular current use of Morse code is by amateur radio operators, although it is no longer a requirement for amateur licensing in many countries. In the professional field, pilots and air traffic controllers are usually familiar with Morse code and require a basic understanding. Morse code is designed to be read by humans without a decoding device, making it useful for sending automated digital data in voice channels. For emergency signals, Morse code can be sent by way of improvised sources that can be easily "keyed" on and off, making Morse code one of the most versatile methods of telecommunication in existence.


Morse Code as an Assistive Technology

Morse code has been employed as an assistive technology, helping people with a variety of disabilities to communicate. Morse can be sent by persons with severe motion disabilities, 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 motion disabilities in addition to sensory disabilities (e.g. people who are also deaf or blind) can receive Morse through a skin buzzer.

In one case reported in the radio amateur magazine QST, an old shipboard radio operator who had a Stroke and lost the ability to speak or write was able to communicate with his physician (a radio amateur) by blinking his eyes in Morse.


Representation and timing

International Morse code is composed of five elements:

  1. short mark, dot or 'dit' (·) — one unit long
  2. longer mark, dash or 'dah' (–) — three units long
  3. intra-character gap (between the dots and dashes within a character) — one unit long
  4. short gap (between letters) — three units long
  5. medium gap (between words) — seven units long[1]

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


Letters, numbers, punctuation

Character Code Character Code Character Code Character Code
A · — J · — — — S · · · 1 · — — — —
B — · · · K — · — T 2 · · — — —
C — · — · L · — · · U · · — 3 · · · — —
D — · · M — — V · · · — 4 · · · · —
E · N — · W · — — 5 · · · · ·
F · · — · O — — — X — · · — 6 — · · · ·
G — — · P · — — · Y — · — — 7 — — · · ·
H · · · · Q — — · — Z — — · · 8 — — — · ·
I · · R · — · 0 — — — — — 9 — — — — ·
Period [.] · — · — · — Colon [:] — — — · · · Comma [,] — — · · — — Semicolon [;] — · — · — ·
Question mark [?] · · — — · · Equal sign [=] — · · · — Apostrophe ['] · — — — — · Plus [+] · — · — ·
Exclamation mark [!] — · — · — — Hyphen, Minus [-] — · · · · — Slash [/], Fraction bar — · · — · Underscore [_] · · — — · —
Parenthesis open [(] — · — — · Quotation mark ["] · — · · — · Parenthesis closed [)] — · — — · — Dollar sign [$] · · · — · · —
Ampersand [&], Wait · — · · · At sign [@] · — — · — ·


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".[2] 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.


Speed Enhancement (Prosigns and Q codes)

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.

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 and Q codes, plus a restricted standardized format for typical messages. 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 pronouns. 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. This use of abbreviations for common terms permits conversation even when the operators speak different languages.

Character(s) Code Character(s) Code Character(s) Code
Wait · - · · ·  Error · · · · · · · ·  Understood · · · - · 
Invitation to transmit - · - End of work · · · - · - Starting Signal - · - · -

Defined in the ITU recommendation.


Learning Morse Code

People learning Morse code using the Farnsworth method, named for Donald R. "Russ" Farnsworth, also known by his call sign, W6TTB, 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. 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.


Alternative display of more common characters for the international code

Some methods of teaching or learning morse code use the dichotomic search table below.

A graphical representation of the dichotomic search table: the user branches left at every dot and right at every dash until the character is finished.     T —  M — —  O — — —  CH — — — —    Ö — — — ·    G — — ·  Q — — · —    Z — — · ·    N — ·  K — · —  Y — · — —    C — · — ·    D — · ·  X — · · —    B — · · ·    E ·  A · —  W · — —  J · — — —    P · — — ·    R · — ·  Ä · — · —    L · — · ·    I · ·  U · · —  Ü · · — —    F · · — ·    S · · ·  V · · · —    H · · · ·
A graphical representation of the dichotomic search table: the user branches left at every dot and right at every dash until the character is finished.
T — M — — O — — — CH — — — —
Ö — — — ·
G — — · Q — — · —
Z — — · ·
N — · K — · — Y — · — —
C — · — ·
D — · · X — · · —
B — · · ·
E · A · — W · — — J · — — —
P · — — ·
R · — · Ä · — · —
L · — · ·
I · · U · · — Ü · · — —
F · · — ·
S · · · V · · · —
H · · · ·

References

  1. [http://www.godfreydykes.info/international%20morse%20code.pdf International Morse Code]. ITU-R M. 1677, 2004. Accessed 2008-01-02.
  2. International Morse Code Gets a New ITU Home, New Character. Accessed February 27 2007.