Posted by Ed Kiser on October 14, 2002 at 18:47:48 from 205.188.209.46 user Kisered.
In Reply to: Morse Code? posted by Ian Wright on October 13, 2002 at 10:06:27:
About the use of MORSE code:
There are three different things that are sent:
1. the DOT
2. the DASH
3. the Silence
A telegraph key can do two things:
1. It can be pressed down to make contact so the electric
current flows.
2. Its natural spring action will lift the key and break
that contact when the key is not being pressed, thus
halting the flow of current.
In this manner, the key is a binary device: The current
either is, or isn't, flowing.
As to the difference between dots and dashes, that is a
matter of the length of time that the current is flowing.
The rate of transmission has to do with defining a UNIT of
TIME. The longer that unit is, the slower the transmission.
One Unit = time it takes to send a dot.
One Unit = time of silence it takes to signal end of dot or
dash.
Two Units = time it takes to send a DASH.
Two Units = time of silence it takes to signal end of
character.
Three Units = time of silence it takes to signal end of
word.
In this manner, a receiver station can be set so a pen makes
a mark when the electricity is flowing, but picks up and
makes no mark during silence. Thus the pen mark shows a
series of short (dot) and longer (dash) marks, with the
length of space between them determining end of
the dot/dash, end of character, or end of word.
This same timing concept can be used to signal with a
flashlight, as one can hold that button down either a short
time or a longer time, and thus one can send the two types
of signals, dot or dash.
The SINGLE FLAG, or WIGWAG signalling:
(following quote from the Boy Scout Handbook.)
"For the flag used with the General Services Code there is
one position and there are three motions. The position is
with the flag held vertically, the signalman facing
directly towards the station with which it desired to
communicate. The first motion (the dot) is to the right of
the sender, and will embrace an arc of 90 degrees, starting
with the vertical and returning to it, and will be made in
a plane that is at right angles to the line connecting the
two stations. The second motion (the dash) is a similar
motion to the left of the sender. The third motion (called
the "Front") is downward directly in front of the sender
and instantly returned upward to the first position. One
front indicates the end of a word and two Fronts, the end of
the sentence. 'AR' is end of message." [Now THAT pair of
letters should be easy for us to remember...]
The end of character is simply a pause with the flag in the
Upright position, as contrasted with the "Front", which is a
DOWNWARD movement to the front.
Pretend for a moment that the PERIOD (I know, a Full Stop
for some of you) is a DOT, and the COLON is the double tap
(like double click on the mouse), and the UNDERSCORE is the
break between signals, and you get
:.:._::.:__:.:._::.:__ (repeated) CQ - hello, ANYONE?
There were several signals that were really just the composite
Of two or more letters, but with no pause between them to
Define the separation of those letters, as:
.:.:. AR - End of Message, ready for next message
:.:.: KA - attention
:.: VA - end of transmission , signing off
...... EEEEEE - error, will repeat last word
.:.:.: RK - period, end of sentence
Messages sent by receiver as replies:
:.: K - ready to receive
::..:. MIN - wait a minute
..::.. IMI - stop sending, please repeat, I did not understand.
.:. R - Acknowledge, message received
This whole concept goes down the tubes when dealing with
tapping. A tap is a tap. After the tap there is silence.
You either hear a tap, or you hear the silence. In this
situation, there is no "length of tap" that can be used to
distinguish a dot from a dash. Continuing to press one's
knuckles to the table after hitting it does not prolong the
length of the sound of the tap.
Just as the use of a mouse has two click modes: the single
click, or the double click, there are two types of taps: a
single tap, or a pair of taps very close together. After
the tap, or taptap, is a pause, whose time is used to
determine if that pause is the end of the character or end
of the word.
It takes a definite sense of rhythm. We started practicing
very slowly, trying to get the sense of timing. For the tap
mode, it was helpful to have some type of sharp marching
type music playing to keep our time consistent. A tap on
the beat, or a taptap, followed by pressing the soft of the
finger on the table, instead of nail (that makes an audible
tapping sound). So the timing was a constant pressing of
the table top at a regular beat. The only difference was,
on the beat, to either use the soft of the finger (silence)
or the finger nail (tap), where a quick pair of taps were
used for dash, but still within the same beat of a single
tap (for dot) would be used. We had an old 78rpm recording
of the Battle Hymn of the Republic that had a good beat to
it, which for learning purposes was just slow enough for us
to learn the technique. We start by just tapping according
to the beat. Nothing all that unusual, as one frequently
taps according to the beat of the music. Then we adjusted
the finger to either tap with the nail, or tap with the soft
flesh of the finger. After getting used to this pair of
taps with the beat of the music, then we start adding the
double tap on the single beat. With this background, it was
not all that bad to continue the beat, but this time with a
pattern of dots/dashes that actually started spelling out
something. The idea of actually keeping the beat during the
pause periods by using the soft flesh of the finger was a
great aid to maintain the time even during the "silent"
portions of the transmission.
It became quite a fun thing in the lunchroom to use the
knife and tap the table top with it to talk to someone in
the next table, with no one else at either table knowing
what we are saying. After all, part of the fun of using
code is to have someone else understand it; but it is also
an important part of any code to have others that cannot
understand what you are doing. That just added to the
thrill.
The rapid double tap meaning dash and a single tap for dot
is also spelled out in my Boy Scout Handbook. That made it
official enough for us.
With this concept from my childhood, it is no wonder than
when the age of computers came into being, and along with it
came the concept of "double-click", it seemed quite a
natural thing to perform that rapid pair. I had been doing
that so many years ago - thanks to Ransome, for without him,
we would not have bothered to even try.
Ed Kiser, South Florida (former Boy Scout, and proud of it.)