Two short beeps. Change the gap, and the letters change.
The spaces between short and long signals follow rules of their own. Place International Morse code’s intervals of 1, 3, and 7 units on the same timeline, and the information carried by silence becomes visible.
Estimated time for the article text only. Allow extra time for figures, comparisons and interactive exhibits.
In International Morse code, gaps carry information along with dots and dashes. With one dot as 1 unit, the gap within a character is 1 unit, between characters 3 units, and between words 7 units. Read the full length of each gap on the same time scale.
How do you divide two short sounds?
You hear two short beeps. Their lengths and number stay the same. Yet lengthen the space between them a little, and in Morse code they become a different sequence of letters.
International Morse code uses spacing to distinguish I, which consists of two short signals together, from EE, two letters each made of one short signal. The gap between the two dots within I is short; the gap between the letters E and E is longer. If you record only the sounding parts as “short, short,” that distinction disappears.
A chart matching short and long signals to characters may show only half the story. Put the time when a signal is present and the time when it is absent on the same horizontal axis. You can then see that the quiet part also has a job: it tells us where the next letter begins.
READ THE COMPARISON / Make a discovery in the diagram
Two dots. Change the gap, and the letters change.
I is one letter with a gap of 1 unit.EE represents two letters separated by a 3-unit gap. Both examples send 2 dots.
| Type | Duration (one dot = 1) |
|---|---|
| Dot / dash | 1 ／ 3 |
| Between signals in one character | 1 |
| Gap between characters | 3 |
| Between words | 7 |
Comparison conditionsTime ratios based on International Morse code in ITU-R M.1677-1. The 3-unit character gap and 7-unit word gap are the full intervals, not additions to the 1-unit gap within a character. No waiting time is added after the final signal in the diagram.
Follow each dot, dash, and gap →See the evidence behind the diagram and the article’s sources
- International Telecommunication Union (ITU) — Recommendation ITU-R M.1677-1: International Morse code (2009 edition, Annex 1) ↗ (opens in a new tab)
- International Telecommunication Union (ITU) — M.1677-1 (10/2009): recommendation listing and current status ↗ (opens in a new tab)
- Library of Congress — First telegraphic message—24 May 1844 (collection record and description) ↗ (opens in a new tab)
- Smithsonian National Museum of American History — Telegraph Register (collection object EM.331408 and description of the recorder) ↗ (opens in a new tab)
The measuring stick is the duration of one dot
Here we use International Morse code as given in ITU Recommendation M.1677-1. The ITU listing checked on November 6, 2026, identifies the 2009 edition as the version in force. The code includes numbers and symbols too, but we will focus first on a few letters to see its structure in time.
If a dot lasts 1 unit, a dash lasts 3. The gap between signals making up a single character is 1 unit; between characters it is 3 units; between words it is 7 units. The same number, 3, serves different roles in a dash with a signal and a gap between characters without one.
When drawing a horizontal strip, use this same scale for the widths of the blank parts as well as the lengths of the colored parts. Stretching color and blank space separately to make them easier to see destroys the crucial ratios. The reading rules are encoded not only in the names “dot” and “dash” but also in proportions of time.
Make three arrangements from the same two dots
Keep the two dots fixed and change only the gap. Start with “signal for 1 unit, pause for 1 unit, signal for 1 unit.” This is the single letter I, lasting 3 units from the start of the first signal to the end of the last.
Make the pause 3 units and the pattern is 1–3–1, totaling 5 units: the two letters EE. Increase the pause to 7 units and the pattern becomes 1–7–1, totaling 9 units: an explanatory example with E as two separate words. This last case is a model isolating the word boundary, not an ordinary English sentence.
Place all three on timelines of the same length and you can see that the sounding portions total 2 units in every case. Only the time without a signal has increased. That difference distinguishes three relationships: within one character, between characters, and between words. Counting the signals alone would miss this information.
A and ET share the same dot and dash, but differ
Now add a long signal. In International Morse code, A joins a dot and a dash within one character. E, meanwhile, is a dot, and T is a dash. Extract only the sounding parts, and both A and ET have the same sequence: short, long.
For A, a 1-unit dot is followed by a 1-unit pause and a 3-unit dash, for a total of 5 units. For ET, the two letters are separated by 3 units, giving a total of 7. The character boundary has changed without adding a single dot or dash.
Think of reading Japanese aloud with pauses that make clear where one group of words ends. That offers a way to grasp the role of the gap. But a gap in International Morse code is not just an expressive pause: it follows a convention with a defined duration. The listener follows both the signal pattern and the boundaries between its groups.
Change the speed while preserving the ratios
Changing how many seconds make up 1 unit lets you send the same code faster or slower. For illustration, set 1 unit to 0.1 seconds. A dot then lasts 0.1 seconds, a dash 0.3 seconds, and a gap between words 0.7 seconds. This is the speed chosen for our model, not a claim that Morse code is always transmitted at these durations.
Change 1 unit to 0.2 seconds and all the corresponding times double. The I above grows from 0.3 to 0.6 seconds, and EE from 0.5 to 1.0 seconds. Even so, the ratio between the gap inside I and the gap between characters remains 1 to 3.
We can therefore consider absolute durations separately from their ratios. Playing the same piece of music more slowly while preserving its rhythm is a useful analogy. What we are aligning here is not pitch or loudness, but the unit of time used to measure signals and gaps.
Do not count the 3-unit gap twice
When drawing your own diagram, it is easy to wonder whether the 3-unit gap between letters should be added to the 1-unit gap between signals. In EE, the entire interval from the end of the first dot to the start of the next is 3 units. It is not a 1-unit pause plus another 3 units.
Use 1 unit within a character, 3 across a character boundary, and 7 across a word boundary. First decide which kind of boundary comes next, then place the corresponding gap. Labeling a blank section “between characters” lets you check its function as well as its length.
The total durations calculated above also run from the start of the first signal to the end of the last. They do not include any wait before transmission begins or after the sequence ends. To compare durations, match the starting and ending points of the calculation too. These code examples also reveal a basic principle of measuring time.
Turn off the sound and look at paper tape
We have explained Morse code through sound, but signals were also recorded on paper. The Library of Congress holds a paper tape recording a transmission from May 24, 1844. Its collection description explains that early equipment embossed dots and dashes that an operator read afterward.
The Smithsonian’s description of a telegraph register explains how pulses traveling through a wire activate an electromagnet that moves a pen or stylus. Clockwork feeds the paper, turning short and long signals into marks. In a model where paper moves at a constant speed, durations can be viewed as lengths of marks and blank spaces.
We cannot simply equate the system preserved on an old paper tape with the current International Morse code table used here. Even so, the idea of turning changes in time into a form that can be read later gives the rows of dots and dashes an added dimension.
Record the empty parts, too
Return to those two short beeps. There are only two sounds, but recording their interval as well lets us explain the difference between I, EE, and E as separate words. The moment we discard “time without a signal,” we lose the boundaries we wanted to preserve.
Of course, an indefinitely long absence of a signal does not always mean a gap between words. What we have compared is the convention for joining two parts within a signal sequence. Understanding what constitutes one message also requires the context of the communication.
Line spacing in books, spaces in text, and the quiet zone around a QR Code each have their own roles. They do not work by the same mechanism as Morse spacing, but they invite us to observe not only conspicuous symbols but also the empty areas around them. Next time you look at a code chart, imagine an invisible time scale behind its dots and dashes.
Sources and verification notes
This article is an original synthesis of primary sources and explanations from specialist institutions.
Generative AI assists with research, structure and English translation. Claims are compared with sources and editorial checks are performed; independent specialist and native-English reviews have not yet been completed.
- International Telecommunication Union (ITU)Recommendation ITU-R M.1677-1: International Morse code (2009 edition, Annex 1) ↗ (opens in a new tab)
- International Telecommunication Union (ITU)M.1677-1 (10/2009): recommendation listing and current status ↗ (opens in a new tab)
- Library of CongressFirst telegraphic message—24 May 1844 (collection record and description) ↗ (opens in a new tab)
- Smithsonian National Museum of American HistoryTelegraph Register (collection object EM.331408 and description of the recorder) ↗ (opens in a new tab)
Sources checked:
The character table in Part I, section 1.1.1, and the duration and spacing rules in sections 2.1–2.4 of Annex 1 to ITU-R M.1677-1 were checked against the PDF text. The durations for I, EE, E as separate words, A, and ET are editorial calculations excluding any additional wait at the end. The choices of 0.1 and 0.2 seconds per unit are explanatory examples, not fixed durations specified by the standard. Historical recording equipment is distinguished from the current International Morse code table. No performance tests of actual radio transmission or reception were conducted.
Rights, status, and revision history
- Status
- Free public edition. Preparation and revision history is retained below.
- 0.1.1
- Rights to the text and diagrams
- The original Japanese text is an independently written summary. The SVG illustrations and conceptual diagrams were newly created. No external images, original source text, or audio recordings are reproduced.
- How sources are used
- Sources are referenced by links only. All rights to each source remain with its respective rights holders.
- · v0.1.0 — Checked primary sources and explanations from specialist institutions, and prepared a private preview article with original comparisons and diagrams. Connected it to the featured reading paths. Publication has not been approved.
- · v0.1.1 — Added a reasoned detour to the v17 Earth & Humanity feature. Existing prose, comparison conditions, sources and source-check dates are unchanged.
For another read, another day.
THE NEXT BOOK
A new question, on the next shelf.
These paths are editorial comparisons and associations. They do not claim that different subjects work by the same principle.
Why does a QR Code need a quiet zone?
Look beyond the main symbols to the structures that make information readable. Morse timing gaps and a QR Code’s spatial margin can be compared while keeping their roles distinct.
How much of a QR Code can be damaged before it stops working?Trace the routes of characters, lines, and pages
Knowing character shapes is not enough: readers also need shared conventions for reading order and grouping.
Books that open to the right or left: the difference goes beyond the lettersExplore clocks with hours that change length
Connect the questions by considering the length of a time unit separately from the rule for dividing time. Unequal hours and transmission speed are not treated as the same system.
Did an Edo-period “hour” change length between summer and winter?From a single code to routes across the world
From the timing rules for sending letters, turn to the systems that carry information and goods over long distances. Whose journeys became shorter, and what new burdens appeared?
What changes when worlds connect?