Samuel F. B. Morse, the inventor of the telegraph, did not invent
the telegraphic code that now bears his name. Actually, today's morse
alphabet is far removed from the system he envisioned for the telegraph.
It consisted only of dots, which expressed numbers, and most common
words and each letter had its own number. This is similar to the
Dian-Ma codes used in Chinese telegraphy.
The one who introduced truly alphabetic telegraphy, with signals of
differing duration (dot and dash) was Alfred Vail. He invented what
was known as American Morse, which was used on landline telegraphs
in the United States until the mid-20th
century. But even this is not what is known as morse code today. What
happened?
When telegraphy was introduced in Germany, the engineer Frederick
Clemens Gerke was set with the task of translating Vail's book on
telegraphy into German. He discovered that the alphabet could easily
confuse the receiving operator, so he proceeded to simplify it. He
removed differing intra-character spacings, and dashes of different
lengths, so that he ended up with a morse code with only two element
lengths (dot and dash), not unlike the present system.
Another few changes were made in the German and Austrian state
telegraph convention of 1852, and the Paris International Telegraph
Convention in 1856. This is the same morse code that was later
adopted all over the world, except for a few minor changes in the
punctuation characters that were enacted in 1939. This alphabet was
known as "continental morse" or "international
morse", but as American Morse faded away, it became simply known
as "morse code", no qualifiers.
The current morse code consists of 5 code elements. These are the dot,
the dash, the intra-character space, the inter-character space, and the
inter-word space. Their duration depends on the speed of sending, but
they have the same relative duration regardless of speed. This relative
duration is based on the length of the dot.
- All elements in a character are separated by a period of silence
equal in duration to a dot.
- One dash equals three dots.
- Characters are separated by a period of silence equal in duration
to a dash.
- Words are separated by a period of silence equal in duration to two
dashes.
Note that these are only platonic ideals; these official durations can
be and are deviated from in hand-sent morse. This applies in particular
to the so-called
Farnsworth method, in which the inter-character spaces are
lengthened. This is used in particular when practicing morse code, where
the characters are sent at a speed of 15
WPM, but the overall text is
slower because of lengthened inter-character-spaces, typically as low as 5
WPM. This is to allow the student to focus on the overall sound of the
character, while still not overwhelming him or her with lots of text
that has to be
buffered in the mind.
Apart from this, telegraphy sent with computers or electronic keyers
more or less perfectly follow standard element durations. It is
particularly important not to lengthen intra-character spaces, or
shorten inter-character ones, as this would make it very difficult to
hear the character boundaries.
When printing code charts, it is customary to use markings that have the
same relationship in length as the actual code elements have in
duration. When this is not technically feasible, such as here on E2,
the period and the hyphen-minus are used for the dot and the dash,
respectively. Intra-character spacing is not given any written
representation.
Letters:
A .-
B -...
C -.-.
D -..
E .
F ..-.
G --.
H ....
I ..
J .---
K, invitation to transmit -.-
L .-..
M --
N -.
O ---
P .--.
Q --.-
R, received .-.
S ...
T -
U ..-
V ...-
W .--
X -..-
Y -.--
Z --..
Á, Å .--.-
Ä, Æ .-.-
É ..-..
Ñ --.--
Ö, Ø ---.
Ü ..--
Numbers:
1 .----
2 ..---
3 ...--
4 ....-
5 .....
6 -....
7 --...
8 ---..
9 ----.
0 -----
Punctuation:
. (period) .-.-.-
, --..--
: ---...
? ..--..
' .----.
- (hyphen-minus) -....-
=, break -...-
/ -..-.
Brackets (parentheses) -.--.-
" .-..-.
; -.-.-.
_ ..--.-
Prosigns:
Beginning of message (KA) -.-.-
End of message (AR) .-.-.
Wait (AS) .-...
Understood (SN) ...-.
Error (correction of last word follows) ........
Distress signal (SOS) ...---...
Finish of transmission ...-.-
In the cases where there is more than one text character per code
character, this means that it depends on context or language. For
instance, .--.- means á in e.g. French messages, and å in
e.g. Swedish messages.
Source:
Pierpoint, William G.: The Art & Skill of Radio-Telegraphy