Morse code is a system that encodes characters using a combination of short (dots) and long (dashes) signals. The three core signal elements that form the foundation of Morse code are dots (.), dashes (-), and spaces. These three basic components can be used to transmit text either as sounds or as pulses of light.
International Morse code uses the following categories of characters:
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Every letter
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Every digit
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Every punctuation mark
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Prosigns
If a translator cannot translate an input character, it will display a special symbol: the number sign (#). This is used when the input is not able to be translated, such as in some instances where the original language does not have the necessary letters, numbers, or symbols.
The timing rule that distinguishes a dash from a dot is the most important part of Morse code. A dash lasts for three times the duration of a dot. If you know how long each signal unit takes, you’ll quickly understand what a character represents. A space between two signal units is also important because it’s a separator.
How Morse Code Is Sent and Interpreted
Early wired Morse telegraphy used electrical pulses and instruments such as registers or sounders; continuous-wave radio tone came later with radio. Today, Morse can be sent as radio tone, keyed carrier, light, sound, or other timed signals.
It may be hard to believe that Morse code is considered one of the earliest forms of digital communication. After all, it relies on discrete signal units rather than continuous analog signals. As such, its structure fits the definition of a digital code quite well.
A very specific Morse distress signal known as SOS is also defined. It consists of three short pulses, followed by three long pulses, then three short pulses again. Modern maritime distress systems no longer rely on SOS as their primary alert, but the pattern remains internationally recognized and can still communicate distress when Morse signaling is the available method.
Unfortunately, automated software decoding of Morse code doesn’t offer 100% accuracy. That’s because real-world conditions introduce inconsistencies into the signal. There’s noise, interference, fading, and other anomalies like “fist” errors, which describe when someone transmits too fast or incorrectly. Character Error Rate measures how many characters are correctly transcribed versus those that are wrong. Because automated decoding can’t always interpret these factors, they don’t offer perfect results.