Morse Code
Morse code encodes text as sequences of short signals (dots, .) and long signals (dashes, -). A dash lasts three dots. Letters are separated by a gap of three dots, words by a gap of seven. It still works where nothing else does: by light, by sound, by key.
+-----------------------------------------------------------------+
| I N T E R N A T I O N A L |
| M O R S E C O D E |
+---------------------+---------------------+---------------------+
| A .- | J .--- | S ... |
| B -... | K -.- | T - |
| C -.-. | L .-.. | U ..- |
| D -.. | M -- | V ...- |
| E . | N -. | W .-- |
| F ..-. | O --- | X -..- |
| G --. | P .--. | Y -.-- |
| H .... | Q --.- | Z --.. |
| I .. | R .-. | |
+---------------------+---------------------+---------------------+
| 1 .---- | 4 ....- | 7 --... |
| 2 ..--- | 5 ..... | 8 ---.. |
| 3 ...-- | 6 -.... | 9 ----. |
| | 0 ----- | |
+---------------------+---------------------+---------------------+
| . .-.-.- | ? ..--.. | / -..-. |
| , --..-- | ! -.-.-- | @ .--.-. |
| : ---... | ' .----. | = -...- |
| ; -.-.-. | " .-..-. | + .-.-. |
| - -....- | ( -.--. | ) -.--.- |
+---------------------+---------------------+---------------------+
| TIMING dot = 1 dash = 3 intra-letter gap = 1 |
| letter gap = 3 word gap = 7 |
+-----------------------------------------------------------------+
| SOS ... --- ... 73 --... ...-- (best regards) |
+-----------------------------------------------------------------+