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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).

Morse code is an early form of digital communication, however unlike modern binary digital codes that use just two states (commonly represented as 1 and 0), it uses five - dot, dash, short gap (between each letter), medium gap (between words) and long gap (between sentences).

Table of contents
1 History of Morse
2 American Morse Code
3 Modern International Morse Code
4 Timing and representation
5 Letters, numbers, punctuation, prosigns
6 Commonly used Morse code abbreviations
7 Conversation with Morse code
8 Morse Code translators

History of Morse

Morse's original code consisted of combinations of dots and dashes 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 dots and dashes, 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 dots, dashes, and pauses. Morse and Vail agreed that Vail's method of representing individual symbols would be included in Morse's patent. This system, known American Morse code, was the version that was used to transmit the first telegraph message.

The code may transmitted 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 (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 dots and dashes (eliminating the pause), is 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 successful lifespan that has not yet been surpassed by any other encoding scheme. Morse code was used as an international standard for maritime 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."

American Morse Code

Virtually extinct, American Morse Code uses a slightly different structure of dots and dashes 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.

This older, alternate 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 clicks from a mechanical sounding device, or often from the sending key which was switched to receive in slave mode when not transmitting.

Most often these operators worked for the railroad or later for Western Union and the like. Thomas Alva Edison was such an operator in his teenage years, as were countless youths of his time.

Modern 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 a steady (unmodulated) 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 very little bandwidth and facilitates communication between amateur radio operators who do not share a common mother tongue and would have great difficulty in communicating using voice modes. It is also very popular among QRP operators.

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 permitting use of the HF bands. Until 1999 proficiency at the 20 WPM level was required to receive the highest level of amateur license (Extra Class); on December 13, 1999, the FCC reduced the Extra Class requirement 13 WPM.

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 is still used by many amateurs, the use of semi- and fully-automatic electronic keyers is prevalent today. Computer software is also frequently employed to produce and decode Morse code RF signals.

Timing and representation

There are two "symbols" used to represent letters, 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.

Letters, numbers, punctuation, prosigns

{| border=1 cellspacing=0 cellpadding=2 ! Letter ! Code ! Letter ! Code |- | 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 | --** |}


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

Common punctuation

Period         *-*-*-
Comma          --**--
Question Mark  **--**
Double Dash    -***-
Hyphen         -****-
Fraction Bar   -**-*

Special Symbols (Prosigns)

Prosigns are dot/dash sequences that have a special meaning. They are composed of two Morse code alphabetic characters "run together"; that is, that omit the normal pause that would occur if they were being sent as two letters of text. They are normally represented in print by the two letters, often with a ligating bar above them.

AR  *-*-*  Stop (end of message), often written +
AS  *-***  Wait (for 30 s - 60 s), respond with C (yes)
K   -*-    Invitation to transmit
           (normally follows AR to indicate 'back-to-you')
SK  ***-*- End (end of contact), sometimes written VA
BT  -***-  Separator, sometimes written =

Not really prosigns, an error may be indicated by any of:

VE  ***-*     I will send the last word again
    ** **     (same)
    ********  Error

Non-English extensions to the Morse code

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

Commonly used Morse code abbreviations

Abbreviations differ from prosigns in that they observe normal interletter spacing; that is, they are not "run together" the way prosigns are.

AA    All after (used after question mark to request a repetition)
AB    All before (similarly)
ARRL  American Radio Relay League
ABT   About
ADS   Address
AGN   Again
ANT   Antenna
BN    All between
BUG   Semiautomatic key
C     Yes
CBA   Callbook address
CFM   Confirm
CLG   Calling
CQ    Calling any station
CUL   See you later
CUZ   Because

CW Continuous wave CX Conditions DE From DX Distance (sometimes refers to long distance contact) ES And FB Fine business (Analogous to "OK") FCC Federal Communications Commission FER For FREQ Frequency GA Good afternoon or Go ahead (depending on context) GE Good evening GM Good morning GND Ground (ground potential) GUD Good HI Laughter HR Here HV Have LID Poor operator MILS Milliamperes NIL Nothing NR Number OB Old boy OC Old chap OM Old man (any male amateur radio operator is an OM) OO Official Observer OP Operator OT Old timer OTC Old timers club OOTC Old old timers club PSE Please PWR Power QCWA Quarter Century Wireless Association R I acknowledge or decimal point (depending on context) RCVR Receiver RPT Repeat or report (depending on context) RST Signal report format (Readability-Signal Strength-Tone) RTTY Radioteletype RX Receive SAE Self addressed envelope SASE Self addressed, stamped envelope SED Said SEZ Says SIG Signal SIGS Signals SKED Schedule SN Soon SOS international distress call SRI Sorry STN Station TEMP Temperature TMW Tomorrow TNX Thanks TU Thank you TX Transmit U You UR Your or you're (depending on context) URS Yours VY Very WDS Words WKD Worked WL Will WUD Would WX Weather XMTR Transmitter XYL Wife YL Young lady (used of any female) 73 Best regards 88 Love and kisses

See also: Q code

Conversation with Morse code

The skill to have sensible conversations with Morse is more than knowing just the alphabet. To make communication efficient, there are many internationally agreed patterns of communication.

A sample cw conversation between station 1 (s1) and station 2 (s2)


CQ CQ CQ de s1 K
Calling anyone (CQ), this is (de) s1, listening (K)
s1 de s2 K
Calling s1, this is s2, listening
(Now we have a connection)

Stations weren't chatting a lot above, just testing a connection. VA, meaning bye or end, is sent as one letter "..._._" and can thus be marked either SK or VA.

Morse Code translators

There are a number of translators on the Web that will convert text to morse code, and play it via a PC: