(Source Wikipedia). In 1934, the Parisian pneumatic network reached its peak with a length of 427 km 2 , it served the 130 offices of the capital and distributes about ten million correspondence per year with a maximum of 30 million messages for the year 1945. Tubist postmen, recruited from the age of 14, distributed the “little blues” on foot, by bicycle and, from 1930, by moped to convey mail to the suburbs. The tubes have different diameters depending on the flows used, the sliders circulate at a speed of 400 meters at 1km per minute.

​

Louis Gaillard, a freshly graduated engineer from the École Nationale Supérieure des Télécommunications, was put in charge of the network's driving force workshops in 1932. A few months later, he found himself at the head of the entire department, a position he held until in 1974. His takeover of the tire network gave the service a new modern impetus.

At the same time, Louis Gaillard developed the automation of the   network: automatic dispatch of cursors, selection of addresses thanks to a system of feelers and contacts carried by the cursors, automatic ejection in the receiving buckets.