thumb|right|This Morse key was originally used by [[Gotthard railway#The Gotthard railway telegraph network|Gotthard railway, later by a shortwave radio amateur.]]

[[File:International Morse Code.svg|class=skin-invert-image|thumb|upright=1.2|Chart of the Morse code 26 letters and 10 numerals

Morse code can be memorized and sent in a form perceptible to the human senses, e.g. via sound waves or visible light, such that it can be directly interpreted by persons trained in it. Morse's original telegraph receiver used a mechanical clockwork to move a paper tape. When an electrical current was received, an electromagnet engaged an armature that pushed a stylus onto the moving paper tape, making an indentation on the tape. When the current was interrupted, a spring retracted the stylus and that portion of the moving tape remained unmarked.

In his earliest design for a 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 English language letter frequency by counting the movable type he found in the type cases of a local newspaper in Morristown, New Jersey. In the Royal Australian Navy, Morse was still regarded as crucial, for example during very close quarters replenishment at sea, when it is transmitted by signal flags so as to avoid the use of radio transmitters while fuel is being transferred between ships. For example, the Android operating system versions 5.0 and higher allow users to input text using Morse Code as an alternative to a keypad or handwriting recognition.

Morse messages are generally transmitted by a hand-operated device such as a telegraph key, so there are variations introduced by the skill of the sender and receiver — more experienced operators can send and receive at faster speeds. In addition, individual operators differ slightly, for example, using slightly longer or shorter dahs or gaps, perhaps only for particular characters. This is called their "fist", and experienced operators can recognize specific individuals by it alone. A good operator who sends clearly and is easy to copy is said to have a "good fist". A "poor fist" is a characteristic of sloppy or hard to copy Morse code.

Digital storage

Morse code is transmitted using just two states (on and off). Morse code may be represented as a binary code, and that is what telegraph operators do when transmitting messages. Working from the above ITU definition and further defining a bit as a dot time, a Morse code sequence may be crudely represented a combination of the following five bit-strings:

  1. short mark, dot or dit (): '1'b
  2. longer mark, dash or dah (): '111'b
  3. intra-character gap (between the dits and dahs within a character): 0
  4. short gap (between letters): '000'b
  5. medium gap (between words): '0000000'b

The marks and gaps alternate: Dits and dahs are always separated by one of the gaps, and that the gaps are always separated by a dit or a dah.

A more efficient binary encoding uses only two-bits for each dit or dah element, with the 1 dit-length pause that must follow after each automatically included for every 2 bit code. One possible coding is by number value for the length of signal tone sent one could use '01'b for a dit and the automatic single-dit pause after it, and '11'b for a dah and the automatic single-dit following pause, and '00'b for the extra pause between letters (in effect, an end-of-letter mark). That leaves the code '10'b available for some other purpose, such as an escape character, or to more compactly represent the extra space between words (an end-of-word mark) instead of (only 6 dit lengths, since the 7th is automatically inserted as part of the prior dit or dah).

Although the dit and inter-letter pauses work out to be the same, for any letter containing a dah, the two-bit encoding uses digital memory more compactly than the direct-conversion bit strings mentioned above. Including the letter-separating spaces, all International Morse letter codes pack into 12 bits or less (5 symbols), and most fit into 10 bits or less (4 symbols); most of the procedural signs fit into 14 bits, with a few only needing 12 bits (5 symbols); and all digits require exactly 12 bits.

For example, Morse ( + 2 extra empty dits for "end of letter") would binary-encode as '11'b, '11'b, '01'b, '00'b; when packed it is = 'F4'x, which stores into only one byte (two nibbles) (as does every three-element code). The bit encoding for the longer method mentioned earlier the same letter would encode as '1110'b, '1110'b, '1000'b = = 'EE8'x, or one-and-a-half bytes (three nibbles). The space saving allows small devices, like portable memory keyers, to have more and longer International Morse code sequences in small, conventional device-driver microprocessors' RAM chips.

Cable code

The very long time constants of 19th and early 20th century submarine communications cables required a different form of Morse signalling. Instead of keying a voltage on and off for varying times, the dits and dahs were represented by two polarities of voltage impressed on the cable, for a uniform time. which uses the full target speed from the outset but begins with just two characters. Once strings containing those two characters can be copied with 90% accuracy, an additional character is added, and so on until the full character set is mastered.

In North America, many thousands of individuals have increased their code recognition speed (after initial memorization of the characters) by listening to the regularly scheduled code practice transmissions broadcast by , the station at the American Radio Relay League's headquarters or by listening to the archived recordings available at its website. the United States military taught Morse code as an 81 day self-paced course, having phased out more traditional classes.

Mnemonics

thumb|right|[[Scouting|Scout movement founder Baden-Powell's mnemonic chart from 1918]]

Visual mnemonic charts have been devised over the ages. Baden-Powell included one in the Girl Guides handbook

<!-- End of "refs=" -->

  • — 200&nbsp;hours of at increasing speeds plus an ASCII-to-CW file generator program.
  • Archived at Ghostarchive and the Wayback Machine: