Oldest operational computer

On Fri, 15 Feb 2008, dwight elvey wrote: The term "audion" describes a circuit for the demodulator stage in a radio set consisting of a tube (mostly called the audion tube like the common REN904). An audion may also be called a "grid rectifier". Sometimes the audion tube was also used as RF amplifier in a reflex circuit. But perhaps you're thinking of Lee DeForest's triode which he called Audion because of it's usage in a thereby called "audion circuit". But with the invention of the frame grid tube ("Spanngitterr?hre") and the PCC88 (called the "miracle tube" or "Wunderr?hre") it has been proved that triodes do much better in RF input stages like in UHF TV tuners which need to go up to around 800 MHz. The PCC88 (and similar tubes like the PCC189) are mostly used in cascode circuits with e.g. a PC93 as UHF oscillator. But we're completely off-topic now... (except perhaps with the frame grid tubes). Christian