Some Unanswered Questions
John Grist Brainerd · Technology and Culture · 1970
There are three men basically concerned with the question before us: Heaviside, Pupin, and Campbell. Heaviside had summarized his work in his Encyclopaedia Britannica article written in June 1902. After discovering earlier the famous law that R/L equals G/C for distortionless transmission over an ideal uniform transmission line, he definitely decided that an increase in L (inductance per unit length) was needed and said in the 1902 article: writer invented a way of carrying out the principle other than uniformly, and recommended it for trial; viz., by the insertion of inductance coils in the main circuit at regular intervals, say one per mile, according to circumstances.... The action of the coils is similar to that of small detached loads placed upon a string to give it inertia, and enable it to carry waves farther (cf. Pupin's claim of the idea of loading based on the string analogy in 1894). Further in the same paragraph Heaviside said: Hence experiment alone can decide how few the coils need be for telephony through a distance far exceeding that possible without the Nothing particular has been done in Great Britain to carry out the writer's invention; but in America some progress has been made by Dr. Pupin, who has described an experiment supporting its practicability; the length telephoned through was increased five times by inserting the coils. It is noteworthy that Heaviside apparently knew only of Pupin's work, and that he seemed to consider it an experiment in support of his theory. Meanwhile, Campbell was studying the same problem, probably