Illustration of Baudot telegraph system showing telegraph operators at the central bureau in Paris, France, using the Baudot telegraph system. This had a keyboard with five keys to enter a message to be transmitted as a series of electric pulses. The system was invented by French engineer Emile Baudot (1845-1903) in the 1870s, and was the first truly digital code. Incoming messages were decoded and printed onto a length of ticker tape. Skilled operators could send 180 letters per minute. Printed in 'Electricite' (1911) by Max de Nansouty, part of the 'Les merveilles de la science' series by Louis Figuier.