A nonode is a type of thermionic valve that has nine active electrodes. The term most commonly applies to a seven-grid vacuum tube, also sometimes called an enneode. An example was th
EQ80
UQ80, which was used as an FM quadrature detector. It was developed during the introduction of TV and FM radio and delivered an output voltage large enough to directly drive an end

pentode A pentode is an electronic device having five electrodes. The term most commonly applies to a three-grid amplifying vacuum tube or thermionic valve that was invented by Gilles Holst and Bernhard D.H. Tellegen in 1926. The pentode (called a ''tripl ...

while still allowing for some

negative feedback Negative feedback (or balancing feedback) occurs when some function (Mathematics), function of the output of a system, process, or mechanism is feedback, fed back in a manner that tends to reduce the fluctuations in the output, whether caused by ...

. As most of the grids were tied together, even an 8-pin Rimlock base was sufficient in the case of the EQ40.

See also