… Thermionic, cold cathode or photo-cathode valves and tubes (for example, vacuum or vapour or …
Explanatory notes
… There are many kinds of valves and tubes, some of which are designed for special purposes such as microwave tubes (e.g., … the electrons from the cathode(s), after being focussed, deflected, etc., fall in the form of a beam on a part of the … producing high frequency oscillations, as amplifiers, as detectors, as scan converters (without the use of a …