Morse speed is measured with one word: PARIS

Morse speed is quoted in words per minute, and the word used is always PARIS — because when sent with standard spacing it occupies exactly 50 dot-lengths, including the gap that follows it. At 20 words per minute that is 1,000 units a minute, so one unit is 60 milliseconds; at 5 words per minute a unit is 240 milliseconds.

The choice of word is not arbitrary and it is not about the city. PARIS was picked because its length in units is close to the average of ordinary English text, so a rate measured against it transfers to real messages.

How does PARIS come to 50 units?

By adding the timing rules together. A dot is one unit, a dash is three, the gap inside a letter is one, the gap between letters is three, and the gap between words is seven.

Each letter total includes the gaps inside it. P is dot, dash, dash, dot — that is 1 + 3 + 3 + 1 = 8 units of signal plus three one-unit gaps between the four symbols, giving 11.

What does that make one unit?

The unit length is 1,200 divided by the speed in words per minute, in milliseconds — which falls straight out of 50 units per word and 60,000 milliseconds per minute.

At 30 words per minute a dot lasts 40 milliseconds — around two frames of video. This is why fast Morse is heard as rhythm rather than counted as symbols; nobody is measuring individual gaps at that speed.

Why is E one dot and Q four symbols?

Because Samuel Morse and Alfred Vail assigned the shortest codes to the commonest letters, and they worked out which letters were commonest by counting the type in a printer’s case. A printer stocked more E than Q, and the code followed the stock.

That makes Morse an early and effective variable-length code, in the same family as the compression schemes used today. Common symbols get short representations, rare ones get long, and the average message is shorter than a fixed-length encoding would produce.

The consequence for a learner is that the easy letters are also the frequent ones, so the first few hours of practice cover most of the text you will meet.

What is Farnsworth timing?

A teaching method that sends each character at full speed while stretching the gaps between them. A learner hearing characters at 18 words per minute with gaps padded out to an effective 8 has time to think without learning the wrong rhythm.

The reason it exists: characters learnt slowly are learnt as counted sequences of dots and dashes, and that habit has to be unlearnt before any real speed is possible. Sending the character at its final speed from the start builds the pattern recognition directly, and only the thinking time is extended.

What about CODEX?

A second standard word, used mainly in some European practice, which comes to 60 units rather than 50. A speed quoted against CODEX is therefore about 20 per cent slower than the same figure quoted against PARIS, and the two are not interchangeable without saying which was meant.

PARIS is the dominant convention and is what an unqualified words-per-minute figure almost always means. Where a piece of equipment or a syllabus specifies CODEX, the arithmetic is the same with 60 in place of 50: one unit is 1,000 milliseconds divided by the speed.

Why is SOS written as one run?

Because it is a prosign rather than three letters. SOS is sent as nine symbols with no inter-letter gaps — a continuous run of three dots, three dashes, three dots — which makes it unmistakable in noise and impossible to confuse with anything nearby.

It was chosen for exactly that property rather than as an abbreviation. The expansions people quote came afterwards, and none of them is the reason.

Questions people ask

Does it handle punctuation? The ITU international alphabet includes the digits and a set of punctuation marks, all of which are supported. Anything without a defined code is reported rather than silently dropped.

Can it do accented letters? A few national variants exist for accented characters and they are not part of the international alphabet, so support for them varies between operators as well as between tools.

Is there a difference between international and American Morse? Yes, and a substantial one. The original American Morse used internal spaces of varying length inside some letters; the international version standardised in the 1860s and is what everything modern uses.

What speed does the audio play at? Slow enough to follow rather than at operational speed. Learning to hear Morse at 20 words per minute takes practice measured in weeks, not a page.

Fifty units to the word, 1,200 milliseconds divided by the speed to the unit, and every other timing follows. The Morse code translator plays the result as well as printing it, the binary translator handles the encoding that replaced it, and the word counter tells you how long the message was before you sent it.