mT tube - mT tube

...Further improvements were made to the triode, such as the tetrode and pentode, and the smaller (low-power) ones are generally called vacuum tubes. After radio broadcasting began (in Japan in 1925), many were made for use in receivers. They were gradually made smaller, moving from the original eggplant-shaped tubes to ST tubes in the 1930s, GT tubes in the 1940s, and mT tubes from the 1950s onwards. As the number of types of tubes increased, the small tubes used in receivers came to be called receiving tubes, and the whole category, including large tubes and cathode ray tubes, came to be called electron tubes. ...

*Some of the terminology explanations that mention "mT tubes" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…さらに三極管を改善した四極管，五極管などが次々に発明され，このうち小型(小電力)のものは一般に真空管vacuum tubeと呼ばれ，ラジオ放送開始(日本で1925年)以後，受信機用として多く作られた。その後当初のナス形管から30年代ST管，40年代GT管，50年代以降mT管としだいに小型化された。また管の種類が増すに従って専門的には受信機に用いるような小型管を受信管と呼び，大型管やブラウン管などを含めた全体を電子管と呼ぶようになった。…

※「mT 管」について言及している用語解説の一部を掲載しています。

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