Relay
Videos
A relay is an electrically operated switch. It consists of a set of input terminals for a single or multiple control signals, and a set of operating contact terminals. The switch may have any number of contacts in multiple contact forms, such as make contacts, break contacts, or combinations thereof.
A relay
An automotive-style miniature relay with the dust cover taken off
Simple electromechanical relay
Latching relay with permanent magnet
Joseph Henry
Videos
Joseph Henry was an American scientist who served as the first secretary of the Smithsonian Institution. He was the secretary for the National Institute for the Promotion of Science, a precursor of the Smithsonian Institution. He also served as president of the National Academy of Sciences from 1868 to 1878.
Historical marker in Academy Park in Albany commemorating Henry's work with electricity
A portrait of Henry dated 1879
Henry's letter at the beginning of the 1876 annual report of Smithsonian Institution, showing the operations, expenditures, and condition of the institution that year