… or vapour or gas filled valves and tubes, mercury arc rectifying valves and tubes, cathode-ray tubes, television …
Explanatory notes
… or vapour or gas filled valves and tubes, mercury arc rectifying valves and tubes, cathode-ray tubes, television … only those valves and tubes which, for different purposes, utilise the effect of electrons emitted from a cathode … valves and tubes, in which the cathode is excited by the action of light. According to the number of their electrodes …