The Marconi Valve Tuner, an early unamplified radio receiver manufactured by the Marconi Company for use on ships to receive wireless telegraphy signals. It used the Fleming valve, the first vacuum tube, invented by John Ambrose Fleming as a detector to rectify the radio wave carrier and extract the Morse code "dots" and "dashes", The set had two valves "(visible at top)"; one was a spare in case the other burned out.