On June 17th, 1874, Jean-Maurice-Émile Baudot (11 September 1845 – 28 March 1903) patented his “Système de Télégraphe Rapide” in France. Many years later (!), Eric Fisher wrote his excellent paper on The Evolution of Character Codes, 1874-1968. On page 1, Fischer says:

I have not been able to obtain a copy of Baudot’s 1874 patent, but his early telegraph probably used the six-unit code (Figure 3) that he attributes to Davy in an 1877 article.

It was actually difficult to find this patent, since the online DB only covers from 1791 to 1855. Fortunately, the nice people at INPI (Institut National de la Propriété Industrielle), particularly Steeve Gallizia were kind enough to allow me access to it.

Eric was correct that Baudot’s system was a “six-unit” code (not to be confused with bits, although in time, they would be related, of course).

Here’s the relevant document:

If you are going to use this document, please quote:

Jean-Maurice- Emile Baudot. Système de télégraphie rapide, June 1874. Brevet 103,898; Source: Archives Institut National de la Propriété Industrielle (INPI)