Early telephone technology. This apparatus, from the 1830s, is based on work by the US inventor Charles Grafton Page (1812-1868) and the Swiss physicist Auguste Arthur de la Rive (1801-1873). Page observed that his induction coil of 1837 could be used to produce sound, work that was extended by de la Rive. This artwork is from a series of illustrated French encyclopedia volumes, published by the Epinal printing firm in the late 19th and early 20th century. The series was called 'Serie encyclopedique des lecons de choses illustrees' (Encyclopedic series of object lessons illustrated), and this example is from a volume published in around 1900.