Systeme Ader (SIT) phone with double receivers

This is the Système Ader (or Ader System) telephone, named after the prolific French inventor Clément Ader, who was a key figure in establishing the first telephone networks in Paris. Clément Ader patented his sensitive carbon pencil transmitter in 1878, which became a foundational component of these early French telephones. The "Système Ader" models were the primary equipment used by the first French telephone companies (such as the Société Générale des Téléphones) starting around 1880. They are visually distinct for their horizontal wooden transmitter boxes and the use of Ader’s "watchcase" receivers, which were more compact than the receivers used in North America at the time. This system remained the standard in France until the nationalization and subsequent standardization of equipment by the PTT in the late 1880s and early 1890s.