GRID

in an electron tube, an electrode that has one or more openings for controlling electrons or ions as they pass through it. Unmodified, the term applies to a control grid, which is ordinarily placed between a cathode and an anode (or plate) of an electron tube to initiate or vary the current between two or more electrodes. A screen gridusually maintained at a fixed potentialis placed between a control grid and an anode to reduce the electrostatic influence of the plate on the control grid. A suppressor grid is interposed between two positive electrodesusually the screen grid and the anodeto reduce the flow of secondary electrons from one to the other.