The Cabinet of Curios

Morse Code

Morse code spells with two lengths of beep and three lengths of silence. Type a message to hear it sent, or hold the key and tap out your own to watch it turn back into letters.

No sound on a phone? Check its silent switch.

Send

Type a message and play it.

Speed

Receive

Tap out code and the tape decodes it.

Hold the knob or Space. A short press is a dot and a long one a dash. Pause to end a letter and pause longer for a space. Watch the marks on the tape run up to the pen.

Follow my pace

Pace

The tree

Every letter is a path. Each dot steps up and each dash steps down. Tap a letter to hear it.

The chart

International Morse code. Tap any character to hear it.

Things to notice

The silences are the separators. A dot lasts 1 unit and a dash 3. The gap inside a letter is 1 unit, the gap between letters is 3, and the gap between words is 7. There's no "end of letter" signal, so a receiver splits letters by listening for the longer quiet. The Receive tape does the same: when the pen passes the letter line the letter is finished and when it passes the space line the word is finished.
Following your pace. Nobody keys at a perfect speed, so the receiver measures your dots and dashes to work out your unit. A press shorter than 2 units is a dot, a quiet longer than 2½ units ends a letter, and a quiet longer than 5½ units ends a word. Those halfway points leave room for a wobbly hand.
Common letters are short. E is a single dot and T a single dash. Samuel Morse and Alfred Vail gave the shortest codes to the letters English uses most, reportedly by counting the type in a printer's case.
Letters fit in four steps. Down to four dots and dashes there are 2 + 4 + 8 + 16 = 30 paths, enough for 26 letters with four left over. Digits all take five and punctuation five to seven.
Speed is measured with PARIS. Morse speed is counted in words per minute, or WPM, using PARIS as the standard word. Everything in Morse is built from one unit, the length of a dot: a dash is 3 units and a word gap is 7. PARIS plus its word gap is exactly 50 units, so 12 WPM is 600 units a minute and each unit is 60 seconds ÷ 600 = 100 ms. Try it from the sample buttons.
SOS isn't three letters. It's sent as one run, ···−−−···, with no letter gaps. Tap it without pausing on the Receive key and see what comes out.

A little history

"What hath God wrought" was the first message on Morse's Washington to Baltimore line in 1844. It was sent in American Morse, an older cousin with different codes and some extra-long dashes. This page uses International Morse, which is what radio operators still use.
Ears beat the paper tape. Morse's receiver was a register that marked dots and dashes on a moving strip of paper, and an operator read the tape by eye. But the register clicked as it marked, and operators found they could decode the clicks as they arrived, faster than reading the tape and with their hands free to write. Companies distrusted this at first, and the Morse company reportedly forbade it. Operators did it anyway. Several were later celebrated as the first to read by sound, including James Leonard in Kentucky in 1848 and Charles Douglas on the Erie Railroad in 1851, though each claim was written decades later by someone championing one man. Paper tape lingered for years, but listening became the job, and telegraph makers eventually sold the sounder, a receiver built only to click, with no paper at all.

Faster than a reflex

A dot lasts 1200 ÷ WPM milliseconds. Even at 5 WPM a dot lasts 240 ms, and at any faster speed it's over before anyone could react to it.

A typical reaction to a beep or a flash~200–250 ms
A dot at 12 WPM, this page's starting speed100 ms
A dot at about 32 WPM, Jesse Bunnell's pace for two hours in 1860~38 ms
A dot at 75.2 WPM, Ted McElroy's 1939 receiving record and about this page's top speed16 ms

Gamers aren't much quicker. Professional esports players are famous for fast hands, but a 2021 study by Bickmann and colleagues found that pros reacted no faster than amateurs or other athletes on simple tests with lights and sounds. Everyone hits roughly the same floor of a couple hundred milliseconds. Pros win by reading the game and anticipating what comes next.

Telegraphers did it for a living. This isn't a modern hobbyist's trick. Once operators learned to copy by ear instead of reading paper tape, copying by sound became the job. Railroads, newspapers, stock exchanges and armies ran on operators listening all day, often at 20 WPM or more, where every dot is 60 ms or shorter.

They did what pros do. Nobody copying at 30 WPM hears dot, dash, dot. Each letter arrives as one sound, a rhythm like di-dah-dit for R, the same way you read a word without spelling it out. Good operators copy several words behind the signal and keep the message in their heads, much like a pro thinking a few moves ahead.

The hands were busy too. PARIS has 14 dots and dashes, so 30 WPM on a straight key means about 7 presses a second, around 420 a minute. That's in the range of the few hundred actions per minute top StarCraft players are known for. In 1860 a 17-year-old Jesse Bunnell sent President Buchanan's last message to Congress at about 32 WPM and kept it up for two hours. Professionals keyed so much that they got "glass arm," a repetitive strain injury, and in 1888 Bunnell invented a sideways key to ease it. Gamers' wrists have the same problem today.

The record is from 1939. Ted McElroy copied 75.2 WPM in a contest that year, and it's still the official record. Some operators say they've copied faster since, but none of those claims are official.

Sources

John Wilson Townsend, Life of James Francis Leonard: The First Practical Sound-Reader of the Morse Alphabet (Filson Club, 1909).
"First in His Line," on Charles W. Douglas, January 6, 1910, page 3, Nebraska Newspapers (University of Nebraska–Lincoln).
George B. Prescott, History, Theory, and Practice of the Electric Telegraph (1860), on the sounder replacing the register, as cited in the Oxford English Dictionary entry for "sounder."