American Morse Code

Two codes, one name

What almost everyone means by Morse code today is the international code, standardised in 1865 and now written down as ITU-R M.1677-1. But it is not the original. The code that went down the first American telegraph lines from 1844, and stayed on the railroads and in the newsrooms well into the twentieth century, is a different system with the same name.

Eleven letters and most of the digits are different. Where the international code makes do with two lengths and one kind of gap, the American code uses four lengths and two kinds of gap - and that extra freedom is exactly what makes it shorter to send and harder to hear.

What is different

• The dash is two units, not three. Everything below is measured against the dot, which stays at one unit in both codes.
• There are two longer dashes. L is a dash of four units, and zero is a dash of five. Nothing like them exists in the international code.
• Some characters contain a pause. C is dot dot, pause, dot. O is dot, pause, dot. R, Y, Z and the ampersand work the same way. That inner pause is longer than the gap between two dots and shorter than the gap between two letters.
• The gaps are tighter. Two units between characters instead of three, three units between words instead of seven.

Put together, that makes the old code noticeably faster on the same key. A full PARIS - the standard measuring word - takes 50 units in the international code and 37.5 units in the American one. Same dot length, a quarter more text per minute.

Why the faster code lost

Because the thing that made it fast made it unusable on radio. The inner pauses are the problem: C and the letter pair IE are the same marks in the same order, separated only by how long a silence lasts. On a landline that was fine. The operator did not listen to a tone, he listened to a mechanical sounder clacking, and later read a paper tape where the gaps were visible as gaps.

Radio took both away. Static fills silences, fading swallows them, and a tone in a headphone gives no visual record at all. A code whose letters differ only in the length of a pause falls apart under those conditions.

So when telegraphy went international and then went on the air, the Continental code - simpler, one dash length, no inner pauses - won. The American code stayed on the wires where it had been born, and went quiet with them.

Where you still meet it

Railroad museums, telegraph clubs and re-enactors keep it alive; the Morse Telegraph Club has members who still work it on sounders. It also turns up in films and games set before the First World War, usually wrongly - the code you hear is nearly always the international one, whatever the year on the screen.

If you already read international Morse, expect to be caught out by the familiar-looking letters rather than the strange ones. F, J, L, O, P, Q, R, X, Y and Z all exist in both codes and mean different things.