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1939 German Ceramic Valve

Wireless World, August 17, 1939.
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A ceramic envelope and base have been used in the construction by Hescho of this latest type of German valve of the same size and shape as the all metal type. The valve electrodes are sealed into the ceramic base and no pinch is employed.

The high frequency screening, in types where it is needed, is effected by spraying a thin layer of metal onto the inside of the Calit cover.

See also the 717A an American HF valve with an IO base and pinchless glass disc construction.

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