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Morse code

Morse code is a system of representing letters, numbers and punctuation marks by means of a code signal sent intermittently. It was developed by Alfred Vail[?] while he was helping Samuel Morse with Morse's invention of the telegraph (1835) which is considered a fore-runner of digital modes of communication (see e-mail).

Morse's original code consisted of sending dots and dashes that represented numbers. Each number represented a word. This required looking up the number in a book to find the word. A telegraph key was then used to beat out the sequence of dots, dashes and pauses that represented the word.

Although Morse invented the telegraph, he lacked technical expertise. He entered an agreement with Alfred Vail[?] who built more practical equipment. Vail[?] developed a code where each letter or symbol is sent individually. Per their agreement Vail's method representing individual symbols was included on Morse's patent. It is this kind of code that was used for the first telegraph message.

The code is transmitted either as an audio tone, a steady radio signal switched on and off (known as continuous wave, or CW), an electrical pulse down a telegraph wire, or as a mechanical or visual signal (eg. a flashing light).

Any code representing written symbols as variable length signals can be called a Morse code in general but specifically the term is used 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" is most commonly used today.

Telegraph companies charged based on the length of the message sent. Elaborate commercial codes were developed that encoded complete 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 networking terminology we would say the commercial code is layered on top of Morse code. 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 dots and dashes which was the forerunner of Morse code.

When considered as a standard for information encoding, Morse code had a succesful lifespan that has not yet been surpassed by any other encoding scheme. Morse code was used as an international standard for ship-to-ship communication until 1999. 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."

International Morse Code

International Morse Code is still in use today (certain parts of the radio spectrum are still(?) reserved only for transmission of morse code signals). Since it relies only on a steady (unmodulated) radio signal, it requires less hardware to send and receive than other forms of radio communication, and it can be used in very high noise / low signal situations, and requires very little bandwidth. Until the 1990s (when did the code-free Tech first appear?), the ability to transcribe morse code sent at 5 words per minute was a requirement to receive an FCC Amateur Radio license in the US using HF bands[?]. 20 WPM was required for the license with highest privileges ("Extra" class).

Amateur and military radio operators skilled in morse code can often understand ("copy") code in their heads at rates in excess of 40 WPM.

Timing and representation:

There are two "symbols" used, called dots and dashes or 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

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.

(Beginners are taught to send short fast letters with small spaces between the dots and dashes in a symbol and exaggerated spaces between symbols and words. This makes it easier to learn.)

People familiar with Morse Code often speak or write it like this. ("Dah" is pronounced with an "awe" vowel sound).

 -- --- *-* *** * / -*-* --- -** *

DahDah DahDahDah DiDahDit DiDiDit Dit, DahDiDahDit DahDahDah DahDiDit Dit.

Here's a table including the alphabet and some other commonly used symbols:

A*- N-*
D-** Q--*-
E* R*-*
G--* T-
I** V***-
K -*-X-**-
M-- Z--**

The numbers are as follows:

 0 -----
 1 *----
 2 **---
 3 ***--
 4 ****-
 5 *****
 6 -****
 7 --***
 8 ---**
 9 ----*

Common punctuation:

 . *-*-*-
 , --**--
 ? **--**
 - -***-
 / -**-*

Special characters:

 error ********
 + *-*-* stop (end of message)
 @ ***-*- end (end of contact)
 SOS ***---*** international distress call.
 Used by the Titanic on April 15, 1912.

It is a common misunderstanding that the SOS is three symbols but the correct way of sending it is as one morse symbol.

Extensions to the Morse Code (nation or language dependent):

 ch ----
 "  *-**-*
 !  **--*

All Wikipedia text is available under the terms of the GNU Free Documentation License

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