Abstract
WITH reference to the letter on the above subject in NATURE of March 3, it may be of interest to record that thermionic amplifiers were applied to the optophone a considerable time ago with the object of increasing the sound in the ordinary telephone, but although it was evident that the sound could be amplified, it was decided that to increase the cost and complexity of the instrument to the extent involved by the addition of an amplifying set was not justified.
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FRENCH, J. [Letters to Editor]. Nature 107, 43 (1921). https://doi.org/10.1038/107043c0
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DOI: https://doi.org/10.1038/107043c0
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