MORSE TELEGRAPH

In America, in 1837, the same year that Cooke and Wheatstone patented their telegraph, Samuel Morse patented his telegraph that was based on coded signals, the well-known dots and dashes. His technique required trained operators but it was much cheaper to install. It needed only a single wire between sender and receiver, using the Earth as return. Over the years a variety of Morse keys and sounders have been produced. The black one in the photograph is a military version. The contacts are enclosed to prevent sparks causing an explosion where gas is present. An intermediate relay (second on the left) was sometimes used on long lines to switch a local battery at the receiver end.