On 4/15/2010 6:11 AM, David Griffith wrote:
I think the Mark and Space stuff has to do with the
fact that the line was always kept energized, thus, an idle line would
hold the sounder arm down. That way you'd know immediately if there was
a line fault. That would be a bit wasteful now, so I suppose I should
preceed each message with a very long dash to at least try to fake that
part.

The original Morse instrument was a device which used a scribe to
imprint a line on a paper tape which was moving past the scribe arm
under tension from a clockwork mechanism.

When the electromagnets were energized, the scribe would make a mark on
the tape. When they weren't, the tape would "space" past the scribe
point without being marked.

Ergo, "Mark" means current in the loop, "Space" means no current. The
early telegraphs were powered by batteries.

There is software available to do what you want to do: visit the Morse
Telegraph Club, http://www.mtc.org/ , for more information.

HTH.

73,

Bill W1AC