Control grid Control grid The control grid is an electrode used in amplifying thermionic valves (vacuum tubes) such as the triode, tetrode and pentode, used to control the flow of electrons from the cathode to the anode (plate) electrode. The control grid usually consists of a cylindrical screen or helix of fine wire surrounding the cathode, and is surrounded in turn by the anode. The control grid was invented by Lee De Forest, who in 1906 added a grid to the Fleming valve (thermionic diode) to create the first amplifying vacuum tube, the Audion (triode). In a valve, the hot cathode emits
William McLellan (American electrical engineer) spent much of his career as an engineer in Caltech's Astronomy department, remaining a consultant there for the rest of his life. He died in 2011 in Pasadena. William McLellan (American electrical engineer) William Howard McLellan (December 1, 1924 – September 30, 2011) was an American electrical engineer, who achieved some fame in 1960 by succeeding at an engineering challenge set by Nobel Prize-winning physicist Richard Feynman. McLellan was born in Casper, Wyoming, grew up in Orland, California, and fought in the Canadian Army in the Second World War. He met his wife Patricia Price in England during the war,