ITU-R M.1677-1 Morse Code Technical Specification

1. The Standard in Brief

This translator implements Recommendation ITU-R M.1677-1, the international specification for Morse code. Every interval in a transmission is a multiple of one unit — the dot: a dash lasts three units, the space inside a character lasts one unit, the space between letters lasts three units, and the space between words lasts seven units. Speed is quoted in words per minute against the 50-unit reference word PARIS, which fixes the unit at 1200 ÷ WPM milliseconds.

That is the whole formula set. For the full treatment — the five timing elements, the PARIS derivation, Farnsworth and Wordsworth spacing, and an interactive timing lab — see the complete Morse code timing guide. The rest of this page documents something different: how the engine shipped on this site actually implements the standard, and how you can verify it.

2. How the Engine Implements Conformance

Fractional units, never rounded. The engine computes the unit as 1200 ÷ WPM milliseconds and keeps it as an exact fractional value through every calculation. At 18 WPM the unit is 66.67 ms; a dash is then scheduled as 3 × 66.67 = 200 ms, not rounded to a whole millisecond first. Because dashes and intra-character gaps are always derived by multiplying that same base unit, the 1 : 3 : 1 ratios hold exactly at any speed — not just at round numbers like 20 WPM.

Farnsworth runs on two clocks. Characters are always formed at the character speed you set, while the gaps follow a second, slower Farnsworth speed: the letter gap is 3 × (1200 ÷ Farnsworth WPM) and the word gap is 7 × (1200 ÷ Farnsworth WPM). Set the Farnsworth speed equal to the character speed and the gaps collapse to the standard 3 and 7 units; lower it and only the silences stretch — the characters themselves never slow down, which is exactly the discipline Farnsworth training is meant to teach.

Synthesized audio with shaped envelopes. Sound is synthesized, never sampled. Playback uses a Web Audio oscillator — a 600 Hz sine wave by default, with a square wave selectable — shaped by an amplitude envelope with 5-millisecond linear attack and release ramps, so keying clicks never reach the speaker. The downloadable WAV export renders the identical schedule offline at 44,100 Hz in mono, prepends 50 ms of silence so a player cannot clip the first dot, and applies the same click-suppression idea with 4 ms envelope ramps.

One honest exception. The duration figure the translator shows before you press play is a straight PARIS estimate at the character speed only — it ignores Farnsworth stretching, so with Farnsworth engaged the real playback runs longer than the estimate. The audio schedule, not the estimate, is the conformance-critical path, and the schedule always follows the rules above.

3. Verification: Worked Examples

You do not have to take any of this on faith — the translator's own counters expose the arithmetic. Type each example into the translator and compare.

PARIS at 20 WPM. The unit is 1200 ÷ 20 = 60 ms. PARIS occupies 50 units once its trailing word space is counted, so repeated at exactly 20 WPM it fills precisely one word per 3.0 seconds — the definitional check the whole PARIS speed standard rests on.

SOS at 20 WPM. The nine elements of ... --- ... total 21 units of tone, and the six intra-character gaps add 6 more: 27 units, which the statistics panel reports alongside a duration of 1.6 seconds (27 × 60 ms = 1.62 s, shown rounded to one decimal).

PARIS at 20 WPM, Farnsworth at 10 WPM. The characters still form at 60 ms per unit, but every letter gap stretches to 3 × 120 = 360 ms instead of 180 ms. Send the same word with Farnsworth set first to 20 and then to 10 and compare: identical character shapes, longer silences — Farnsworth stretching the gaps and nothing else. The timing lab visualizes the same comparison element by element.

4. Procedural Signals (Prosigns) & Q-Codes

In addition to standard letters and numbers, radio operators use procedural signals (prosigns) transmitted without inter-letter pauses:

• SOS (...---...) - Distress signal
• AR (.-.-.) - End of message
• SK (...-.-) - End of contact
• BT (-...-) - Paragraph break