Variable Condenser, Used by Alfred N. Goldsmith, 1920-1930

Condensers (also known as capacitors) allow alternating electrical currents to pass while blocking direct currents. Condensers can block, pass, filter and tune the various currents of the radio. This device was likely used by Alfred Goldsmith for his experiments while he was the Research Director of Radio Corporation of America. Goldsmith aided in the development of the first commercial radio-phonograph.