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Control grid
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<p>The control grid is an <a href="/facts/Electrode/251PaKX8">electrode</a> used in amplifying <a href="/facts/Vacuum_tube/VHd1BNLq">thermionic valves</a> (vacuum tubes) such as the <a href="/facts/Triode/IGbT0RHa">triode</a>, <a href="/facts/Tetrode/WnYG1oVT">tetrode</a> and <a href="/facts/Pentode/HuVlNVSt">pentode</a>, used to control the flow of electrons from the <a href="/facts/Cathode/tqdlGayU">cathode</a> to the <a href="/facts/Plate_electrode/zAkTJdsa">anode</a> (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 <a href="/facts/Lee_De_Forest/tMDkcLnV">Lee De Forest</a>, who in 1906 added a grid to the <a href="/facts/Fleming_valve/vIFvkjRo">Fleming valve</a> (<a href="/facts/Thermionic_diode/JyaoyGnk">thermionic diode</a>) to create the first <a href="/facts/Amplifier/pnRgxncC">amplifying</a> vacuum tube, the <a href="/facts/Audion/IlIhKsJc">Audion</a> (<a href="/facts/Triode/IGbT0RHa">triode</a>). </p>