A nonode is a type of

thermionic valve A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied. The type known as a ...

that has nine active

electrode An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials d ...

s. The term most commonly applies to a seven-grid

vacuum tube A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied. The type known as ...

, also sometimes called an enneode. An example was th
EQ80
UQ80, which was used as an FM

quadrature detector In radio, a detector is a device or circuit that extracts information from a modulated radio frequency current or voltage. The term dates from the first three decades of radio (1888-1918). Unlike modern radio stations which transmit sound (an audi ...

. It was developed during the introduction of TV and FM radio and delivered an output voltage large enough to directly drive an end pentode while still allowing for some negative feedback. As most of the grids were tied together, even an 8-pin Rimlock base was sufficient in the case of the EQ40.

See also