NU22C SILICA VALVE, 1937

The Navy used these valves, The envelope is made of Silica Glass. The advantage being that the envelope could be opened, the unit repaired and easily resealed and evacuated of air. More importantly Silica glass can pass higher proportions of Infra red and has a higher melting point, so the anode of the valve can run at higher temperatures. This is a half wave rectifier of 1937.

A0642