Sylvania 1B40 TR Switch Tube  
Written by AnubisTTP on 2020-09-02  


The Sylvania 1B40 is a small cylindrical TR cell which was likely released sometime during the 1940s. The 1B40 is filled with argon, which produces a purple discharge when the cylindrical keep-alive electrode is energized. This tube is designed to be mounted in an external cavity, which would mate with the grounding ring on the bottom edge of the tube. We do not know the release date of the 1B40, but by 1947 the tube was out of production and no longer readily available.


Sylvania 1B40 switching tube
Sylvania 1B40 TR switch tube, with keep-alive electrode energized.

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