… Thermionic, cold cathode or photo-cathode valves and tubes …
Explanatory notes
… 85.40 ‑ Thermionic, cold cathode or photo-cathode valves and tubes … either in a vacuum or in gas. There are three types : thermionic valves and tubes, in which the cathode must be … light. According to the number of their electrodes they are termed diodes, triodes, tetrodes, etc. The same envelope may …