Valve amplifier thermionic valves. The simplest valve was invented by John Ambrose Fleming while working for the Marconi Company in London in 1904 and named the diode, as it had two electrodes. The diode conducted electricity in one direction only and was used as a radio detector and a rectifier. In 1906 Lee De Forest added a third electrode and invented the first electronic amplifying device, the triode, which he named the "Audion". This additional "control grid" modulates the current that flows between cathode and anode. The relationship between current flow and plate and grid voltage is often represented as a series
Poppet valve in intake valves a pressure differential helps open it. The poppet valve was most likely invented in 1833 by E.A.G. Young of the Newcastle and Frenchtown Railroad. Young patented his idea but the Patent Office fire of 1836 destroyed all records of it. The word poppet shares etymology with "puppet": it is from the Middle English "popet" ("youth" or "doll"), from Middle French "poupette", which is a diminutive of "poupée". The use of the word "poppet" to describe a valve comes from the same word applied to marionettes, which – like the poppet valve – move bodily in response to