Morse Telegraph

Everything here runs from a few volts. Never connect a telegraph line to the mains, and keep the coil circuit isolated from anything else on the bench.

Morse's patent describes a machine that writes the message on a moving paper tape. Reading by ear came later, from operators who found they no longer needed the paper.

Cooke and Wheatstone's system used five wires and five needles. Work out the cost of five wires over a hundred miles — that arithmetic is why coding won.

Wind several hundred turns of enamelled wire on an iron core. Soft iron, so it releases the armature the instant current stops.

Hang a steel lever over the pole so it is attracted when energised. Set the gap small — a big gap needs far more current for the same pull.

Spring the armature away from the pole. Spring tension sets how fast the sounder can follow — too strong and it misses dots, too weak and it sticks down.

Make a pivoted brass lever closing onto a contact. It is only a switch — all the intelligence is in the timing of your hand.

Fix the ratios: dash = 3 dots, gap between elements = 1 dot, between letters = 3, between words = 7. The code is a rhythm, and the ratios are the code.

Drive a paper strip past the armature at constant speed so a stylus marks it. Constant speed is essential — variable speed makes dots and dashes indistinguishable.

Key a few characters and inspect the marks. You are reading duration converted to length — the tape is a chart recorder.

Ignore the tape and listen to the armature clicks. Down-click to up-click is the element length, and most operators found this faster than reading paper.

Tally the letters in any English paragraph. E is far commonest, then T. Compare with the code: E is one dot, T is one dash.

Send the same sentence using the real code, then using five elements per letter. The frequency-weighted version is markedly shorter — that saving IS the invention.

Add resistance in series to simulate distance. Beyond a point the sounder will not pull in — which is exactly the problem the relay was invented to solve.

The patent. US 1,647, "Improvement in the Mode of Communicating Information by Signals by the Application of Electro-Magnetism", granted 20 June 1840 to Samuel Finley Breese Morse. Morse was a professional portrait painter, not an engineer, and two collaborators were essential: Leonard Gale, a chemistry professor who showed him how to wind the electromagnet properly and how to use Joseph Henry's relay principle to extend range, and Alfred Vail, whose mechanical skill produced the working instruments and who has a strong claim to much of the code itself. The first public line, Washington to Baltimore, opened in 1844.

Serial beats parallel when wire is the expensive part. The competing Cooke and Wheatstone telegraph, patented in Britain in 1837, used five wires and five needles that pointed directly at letters on a diamond board — no code to learn, and it worked immediately. Morse's needed operators trained in a code, but it needed ONE wire. Over long distances the wire dominates the cost, so the system that trades hardware for time and training wins. That trade is still being made: it is why serial buses replaced parallel ones inside computers, once signalling got fast enough.

Variable-length coding, a century before information theory. The code assigns short symbols to frequent letters and long ones to rare letters — E is one dot, T one dash, while Q and Y are four elements each. Vail is said to have derived the frequencies by counting type in the cases at a Morristown newspaper office, which is empirical linguistics done with a printer's type tray. This is exactly the principle Claude Shannon formalised in 1948 and that underlies Huffman coding and every compression scheme since. Morse code is a hand-optimised prefix-free variable-length code, arrived at by counting.

Two things worth separating. The code and the apparatus are different inventions with different authorship, and American Morse — the code actually used on US landlines, with internal spaces in some characters — is not the International Morse standardised in 1865 and used ever since. The register that wrote on tape was in the patent and was abandoned in practice within a decade, because trained operators read faster by ear than the machine could print. A patent describing a printing telegraph became, in the field, a listening one.