Around 1835, Joseph Henry in the United States and Edward Davy in England independently developed the electrical relay: a device in which a small current, by activating an electromagnet, opens or closes a higher-power circuit. Henry used it to improve his experimental telegraph, though he never published his experiments, and their dating rests on later testimony from him and his students. Davy deposited a letter describing his relay idea with the British Society of Arts in 1837 and patented it as part of his telegraph system, considered by several historians the first practical, documented design of the device. There is no evidence of contact or influence between the two. The relay became the elementary logical switch of 19th- and early 20th-century electrical automation, and it is the component Torres Quevedo would later use to build the decision-making organs of his automata.