I’ve seen this scene in so many movies it’s pretty much a cliché. A bunch of guys are sunk in a crippled submarine or upturned ship (ala The Poseidon Adventure) or collapsed building and they manage to keep in contact with the outside world via Morse code tapped out through the ships hull or a water pipe with a monkey wrench.
Okay, the dots I can understand. But how would they do the dashes?
Well I am kinda guessing here, but I always thought that dots were done quickly and dashes tended to have a “pause”.
I thought about that, but then how’d you tell the spaces between individual letters?
I think (I’m not sure) that all morse letters are composed of a certain number (5?) of dots and dashes. Therefor there’s no need for a pause between letters.
According to this site:
This sounds great, but it also sounds like it would be really tricky at speed. Hopefully somebody who actually uses this will chime in and clear it up.
The above link shows, unfortunately, that all characters do not have the same number of elements (dots and/or dashes). Letters range from one to four elements; all numbers have five; punctuation marks appear to have five or six.
From this site: http://www.soton.ac.uk/~scp93ch/morse/index.html?http://www.soton.ac.uk/~scp93ch/morse/trans.html
"If the duration of a dot is taken to be one unit then that of a dash is three units. The space between the components of one character is one unit, between characters is three units and between words seven units. To indicate that a mistake has been made and for the receiver to delete the last word send … (eight dots). "
I’m pretty sure that’s wrong…from the little Morse code I still remember, I can recollect that a single dot is “E”, for instance, and most of us know that “S” is three dots, and “O” is three dashes. For some reason, I seem to remember that for a situation like the on in the OP, a dash was two signals sounded very close together, and a dot was by itself.
brad_d, I don’t think that solves the problem here. When you’re hitting a pipe with a wrench, or whatever the situation is, it’s nearly impossible to hit it so that a certain beat is three times longer than the previous one…at least except maybe by hitting it really hard, and letting the noise resonate. Anyway, the guys in the movies never seem to do it that way 
There’s a special emergency version of morse code for upturned boats. It involves many many dots and no spaces or breaks between words. It translates roughly as ‘Getmethefuckoutofhererightnow’. It’s pretty easy to learn.
BANG! BANG! BANG!(PAUSE PAUSE) BANG!(PAUSE)BANG!(PAUSE)BANG!(PAUSE)(PAUSE PAUSE)BANG! BANG! BANG!
Repeat until rescued or drowned.
Just in case you’re ever in the engine room of a burning capsized ocean liner.
b.
This link describes a code used by American POW’s during Vietnam that was devised to solve this exact problem with Morse code. You’d think they would have just used Morse code if it was that easy to get around the dillema.
The old-time railroad telegraphers used a “clicker” with an electromagnet to receive telegraphic code sent over wires. Modern radiotelegraphers listen to the audio output of oscillators, which yield long and short duration audio tones. A skilled Morse-coder recognizes the rhythm of the code groups, and can recognize the letters that way. Thus, the code-adept can decipher the pattern of the letters, even if they are tapped out on a tabletop. It is the duration of the pauses between the taps that allows this.
It requires an adept sender and receiver.
KN6SU
Andy, that is some funny shit!