Radio receiver components. Radio technology was developed in the 1890s, with new detectors used as the technology progressed. At top is an electrolytic Jegou detector. At centre and bottom, is a crystal detector in horizontal and vertical views. Crystal radio receivers were first built around 1900, and used crystalline minerals to detect radio signals. Photograph published in 'La Telegraphie Sans Fil' (Wireless Telegraphy, 1914), by the French geophysicist Alphonse Berget (1860-1934).