Excerpt from The Thermionic Valve and Its Developments in Radio-Telegraphy and TelephonyThe present extensive use of appliances in modem radiotelegraphy and radiotelephony based on the thermionic emission from an incandescent cathode in a vacuous bulb, of which the Fleming oscillation valve was the first representative, has given rise to much published information on the subject in technical journals as well as to numerous patent specifications. Since most of the recent great advances in wireless telegraphy and telephony are dependent on the employment of these inventions it seemed desirable to collect together in a single volume some of this literature for the assistance of radio-engineers. The author, therefore, accepted the invitation of The Wireless Press, Limited, to write a small book on the practical side of the subject.It has not been deemed necessary to enter very fully into the purely scientific researches on thermionic emission from incandescent substances, because it has already been treated very fully by Prof. O. W. Richardson in his excellent monograph, The Emission of Electricity from Hot Bodies (Long-mans, Green & Co., London).The introductory chapter of the present volume, nevertheless, provides a brief sketch of the researches which led up to the practical applications described in subsequent chapters. The author has, however, felt it necessary to explain in rather full detail the history of this practical application by himself and others, and of the patent litigation which has taken place in the United States and in Great Britain in connection with it, on account of the efforts which have been made to depreciate the Author's work on this subject. The legal judgments in these actions are printed as an appendix, and will enable the reader to view the questions of priority of invention from the standpoint of unbiassed and competent judges.One other matter calls for remark, and that is the question of nomenclature.
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