Émile Baudot

Jean-Maurice-Émile Baudot (; 11 September 1845 – 28 March 1903) was a French telegraph engineer and inventor of the first means of digital communication Baudot code. He was one of the pioneers of telecommunications. He invented a multiplexed printing telegraph system that used his code and allowed multiple transmissions over a single line. and patented it in 1874. It was a 5-bit code, with equal on and off intervals, which allowed telegraph transmission of the Roman alphabet, punctuation and control signals. By 1874 or 1875 (various sources give both dates) he had also perfected the electromechanical hardware to transmit his code. His inventions were based on the printing mechanism from Hughes' instrument, a distributor invented by Bernard Meyer in 1871, and the five-unit code devised by Carl Friedrich Gauss and Wilhelm Weber. Baudot combined these, together with original ideas of his own, to produce a complete multiplex system.

Baudot system

On 17 June 1874 Baudot patented his first printing telegraph (Patent no. 103,898 "Système de télégraphie rapide"), in which the signals were translated automatically into typographic characters. Baudot's hardware had three main parts: the keyboard, the distributor, and a paper tape.

Each operator - there were as many as four - was allocated a single sector. The keyboard had just five piano type keys, operated with two fingers of the left hand and three fingers of the right hand. The five unit code was designed to be easy to remember. Once the keys had been pressed they were locked down until the contacts again passed over the sector connected to that particular keyboard, when the keyboard was unlocked ready for the next character to be entered, with an audible click (known as the "cadence signal") to warn the operator. Operators had to maintain a steady rhythm, and the usual speed of operation was 30 words per minute.