Having said that, to reflect the title itself I don't think Morse code has a very good bang-for-buck ratio for kidnapping.
Absolutely most people never get kidnapped, it's a very rare occasion statistically. Learning Morse code is not enough: you will have to use it repeatedly to keep remembering it, and I don't think you need Morse code very much in general life so you'll need to exercise your skills intentionally just in case a very unlikely event would happen. Further, to benefit from Morse code while being kept hostage you will need some medium through which to transfer knocks or beeps and you need another party who is both listening and can read Morse code.
It might make sense if your lifestyle calls for higher risks to be kidnapped, but even then I think there are wiser ways to spend your minutes trying to avoid being kidnapped in the first place.
Although I don't know how true this is, I've tried to keep to this in other interfaces, avoiding three-blink patters on lights when someone is not in trouble.
There's a General Alarm signal (above), but no Abandon Ship signal. The captain gives those manually.
(I may be blatantly wrong!)
The General Alarm typically calls for the crew to proceed (at haste!) to the muster station to be informed of the nature of the emergency and be put to work handling the situation.
Luckily, I've only ever had to abandon ship during a couple of drills.
Just be alert. The world needs more lerts.
And the sign on the inside of your trunk / boot is a triangle.
Woah I had no idea!
For those that don't want to click, it's a commercial for a brand of dish cleaner named S.O.S. There are dirty pots and pans that clang out the S O S message in Morse code, with subtitles spelling out the letters as they come out. A screen appears at the end asking "are your dirty pots trying to tell you something?"
Wearing close that easily shred so you can hang small pieces of your shirt on nearby bushes as a trail.
Or unique pieces of jewelry you can drop along the way for the Ranger to find.
It also doesn't hurt to have at least 2 days of laundry in the basket so the blood hounds have something to scent from.
E . T -
I .. A .- N -. M --
S ... U ..- R .-. D -..
H .... B -... L .-.. F ..-. V ...-
W .-- K -.- G --. O ---
Z --.. C -.-. X -..- P .--.
J .--- Y -.-- Q --.-
Most successful learners use the Koch method, which transmits characters at 20wpm equivalent speed but with longer gaps between each character. You start by learning to distinguish two similar letters (A and N or K and R), then adding letters one by one. Learning at slower speeds or using a visual letter chart is actively harmful - it encourages you to count dots and dashes rather than listening to the sound of each letter as a complete rhythmic pattern. The order in which you learn the letters is largely unimportant.
Looking in to it, I see there's two ways - Farnsworth & Koch. The downside of the former is that you get stuck with slow speed and have a harder time to get faster. The downside of the latter is that the initial learning process seems more pointless because there's no actual words.
> In his earliest code, Morse had planned to transmit only numerals, and to use a codebook to look up each word according to the number which had been sent. However, the code was soon expanded by Alfred Vail in 1840 to include letters and special characters, so it could be used more generally. Vail estimated the frequency of use of letters in the English language by counting the movable type he found in the type-cases of a local newspaper in Morristown. //
M  is always well down the frequency in general lists. I wonder if Vail's corpus was biased, whether he discounted local names.
Interesting to note that Morse planned a code using a dictionary; should we be calling it Vail code?
Knowing that it's Morse code for the title of the song, I can reconstruct the individual codes for the letters AEHMOSTVW.
If someone were to write a hit song containing the whole Morse alphabet in a way that gets stuck in your head easily like in this Camille song, we might all learn it without trying.
> However although they work well for other people, I still find my cheek operated switch easier and less fatiguing to use.
When comparing how many physical actions are necessary per letter in morse code, vs this  example of him using his speech synthesizer, it's a lot more obvious.
I don’t think the idea is worthless, just not worth as much as what others may think.
In the Hardy Boys book “Hostages of Hate”, Frank Hardy’s girlfriend, Callie Shaw, is kidnapped and is able to send a secret message to Frank by blinking her eyes on a video recording.
Funny what sticks in your mind from a young age.
kidnapped by terrorists and forced to read a statement.
IIRC this was used in Homeland, the TV show.
I would assume to effectively use Morse code, you’ll need a way to convey short silence, long silence, short beep, and long beep. Knocking misses the long beep.
Not that I have known this before, but people talk about it in TFAs comments as 5x5.
What I guess you can do is vary the acoustics of your knocks (think knuckles vs palm) but this will require the recieving party to do much more processing when decoding.
shave and-a hair cut... two! bits! 
match in-the gas tank... boom! boom! 
Meanwhile, a rimshot, involving two drum hits and a cymbal crash offers two channels of interpretation.
ba-dum tiss! 
But there also are alternative codes for knocks, e.g. doing two groups of 1-5 knocks per letter (=25 letters encoded)
I think that's a bit of an oversimplification since there's no ambiguity in text about where one letter ends and the other begins. The issue isn't spacing between words, it's spacing between _letters_
I assume your parent comment interpreted the spurious requirement for "long pause" as an assumption that for communication to take place, you'd have to have a robust distinction between letter spacing and word spacing.
The VOR does not account for the aircraft heading. It only
relays the aircraft direction from the station and has the same indications regardless of which way the nose is pointing. Tune the VOR receiver to the appropriate frequency of the selected VOR ground station, turn up the audio volume, and identify the station’s signal audibly. Then, rotate the OBS to center the CDI needle and read the course under or over the index.
Say a pilot is flying by reference to Avenal VORTAC. She would tune a nav radio to 117.1 and listen for Morse code tones AVE, the station’s identifier and helpfully printed on the chart for quick reference. Nice avionics units will perform this translation for the pilot.
: FAA Instrument Flying Handbook, https://www.faa.gov/regulations_policies/handbooks_manuals/a...
> Denton was forced by his captors to participate in a 1966 televised propaganda interview which was broadcast in the United States. While answering questions and feigning trouble with the blinding television lights, Denton blinked his eyes in Morse code, spelling the word "TORTURE"—and confirming for the first time to U.S. Naval Intelligence that American POWs were in fact being tortured. 
You can see the video  on Youtube.
Alas, I have lost the ability. Everything is gone.
The world record in sending letters (random 5 letter groups) is 283 for one minute: http://www.hst2017.org/en/records
This is with a special key that's made for high speed telegraphy. Anything on a mobile device would most likely be a lot slower.
There are some sample sounds of similar speeds, which you may find interesting.