Editing Control grid (section)

== Construction ==
[[Image:Triode-english-text.svg|right|thumb|Structure of a modern low-power triode vacuum tube.  The glass and outer electrodes are shown partly cut away to reveal the construction.  ]]

The grid in the first triode valve consisted of a zig-zag piece of wire placed between the filament and the anode.  This quickly evolved into a helix or cylindrical screen of fine wire placed between a single strand filament (or later, a cylindrical cathode) and a cylindrical anode. The grid is usually made of a very thin wire that can resist high temperatures and is not prone to emitting electrons itself.  [[Molybdenum]] [[alloy]] with a [[gold]] plating is frequently used.  It is wound on soft [[copper]] sideposts, which are swaged over the grid windings to hold them in place.  A 1950s variation is the frame grid, which winds very fine wire onto a rigid stamped metal frame. This allows the holding of very close tolerances, so the grid can be placed closer to the filament (or cathode).