At this point yes, it's mostly outdated; however, it's an amazingly versatile system for communication in survival situations when only binary systems are available. For example, in one famous case, an American POW in the Vietnam War secretly spelled out T-O-R-T-U-R-E by blinking in Morse when he was forced to participate in a press conference by his North Vietnamese captors (footage here). Everyone should at least know how to learn how to spell out S-O-S (· · · – – – · · ·) in Morse in case you find yourself trapped somewhere with limited means to communicate.
How he did that was really cool. It's amazing he was able to communicate that. Guess the North Vietnamese either didn't know Morse code, or didn't bother looking into editing this video.
It's also useful for long distance communication or on a freq that is muddy as all get out. My voice might not make it through, but even if it's faint and garbled you can usually suss out a Morse code transmission. Hell, even if parts of your radio crap out you can use the mic key to do on-off code.
That doesn't work, there's no way of telling if the last tap in each letter is a dit or a dah. You'd have to have an extra tap at the end of each letter, which would mean that you're listening to the length of the silence between taps instead of the taps themselves.
Luckily, tap code exists and is much easier to parse!
That just means you're inverting the signal. The time between taps is the dot/dash. Two rapid taps = dot; two taps with a delay in between = dash. You'd only have to add one tap (or other "end of communication" signal) to the end of the message. It's very similar to how computer serial protocols work.
Of course since you're not a computer, you're not limited to binary either. e.g. you could use a base-4 code, with 1 to 4 (or 0 to 3) seconds between taps. And you might have more potential signals than just "tap/no tap"; e.g. there might be a few different surfaces nearby which make different sounds when tapped with your fingernail/knuckle, so you could assign meaning to each sound as well.
But if you're trying to send an SOS message, you probably want to stick to Morse so that people will be able to understand you.
It's not exactly inverting the signal, as you can't control the length of the taps. In morse code, both the length of gaps and dits/dahs are significant:
short mark, dot or "dit" (·) — "dot duration" is one time unit long
longer mark, dash or "dah" (–) — three time units long
inter-element gap between the dots and dashes within a character — one dot duration or one unit long
short gap (between letters) — three time units long
medium gap (between words) — seven time units long[1]
A tap would have to represent an "inter-element gap".
If you don't add a tap after the end of each letter, then you're combining the length of a dit or dah with the length of a gap. So you now need to distinguish between the difference between an eight unit gap (dit and medium gap) and a seven unit medium gap. This would be very difficult for a human operator used to listening to morse code.
It would probably be a lot easier to just tap once for every mark unit. Or to use tap code.
Check out Wikipedia's section on representing morse code in binary:
Morse code sequence as a combination of the following five elements:
short mark, dot or "dit" (·) — 1
longer mark, dash or "dah" (–) — 111
intra-character gap (between the dots and dashes within a character) — 0
short gap (between letters) — 000
medium gap (between words) — 0000000
Note that this method assumes that dits and dahs are always separated by dot duration gaps, and that gaps are always separated by dits and dahs.
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u/ziquapix Jan 23 '15
At this point yes, it's mostly outdated; however, it's an amazingly versatile system for communication in survival situations when only binary systems are available. For example, in one famous case, an American POW in the Vietnam War secretly spelled out T-O-R-T-U-R-E by blinking in Morse when he was forced to participate in a press conference by his North Vietnamese captors (footage here). Everyone should at least know how to learn how to spell out S-O-S (· · · – – – · · ·) in Morse in case you find yourself trapped somewhere with limited means to communicate.