… vacuum or vapour or gas filled valves and tubes, mercury arc rectifying valves and tubes, cathode-ray tubes, …
Explanatory notes
… vacuum or vapour or gas filled valves and tubes, mercury arc rectifying valves and tubes, cathode-ray tubes, … emitted from a cathode either in a vacuum or in gas. There are three types : thermionic valves and tubes, in which the … for cathode‑ray tubes, deflection coils for mounting around the necks of cathode‑ray tubes for scanning purposes. …