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ID = 25210
United States of America (USA)
Brand: RCA (RCA Victor Co. Inc.); New York (NY)
Tube type:  TRANSMITTING TUBE (general)   VHF 
  Ca. 1925 up to 1945 very rare. ***
Identical to 8D21

Base SPECIAL TUBEBASE in general 2 Top contacts.
Filament Vf 3.2 Volts / If 125 Ampere / Direct / Specified voltage AC/DC

Dual tetrode developed by RCA for television broadcasting.
Advertised in Electronics, February 1947, page 63.

The metal to glass seal used in this tube was originally invented by William G Housekeeper in 1922. Housekeeper worked at the Western Electric Co in Kearney, New Jersey at the time. His invention was known as the Housekeeper seal and was a key development, used in many later transmitting tubes

Text in other languages (may differ)
Information source -- Original prospect or advert   

8d21_rca_sock_1.png 8D21: RCA TT
Götz Linss † 27.06.21

8D21: RCA TT
Götz Linss † 27.06.21

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