Fifty years progress in electrical communications

A MISSIONARY EFFORT WHICH SUCCEEDED I trust that I will be pardoned for speaking now about my own missionary efforts among the unbelievers in the telegraph and telephone industries. I began to make these efforts a few years after Hertz, by his classical experiments, had clarified my ideas and everybody else's ideas concerning Maxwell's meaning. At that time I had never even heard of Heaviside or of Vaschy and of their advocacy of high inductance, but I had heard from my friends in the telephone industry of the inefficiency of telephonic transmission and of the failures to improve it by increased inductance. It was obvious that the increase which they described was too small and full of absorptive losses. Highly efficient coils of large inductance inserted at periodically recurring intervals into the line was the remedy which I proposed. But I was told that the remedy had been tried and that a dismal failure had resulted. I was also reminded that universal experience recommended the removal of inductance coils from telegraph and telephone lines; their interference with transmission, they said, had earned for them the opprobrious name “choke coils.” It was clear that I had to furnish a proof which would convince even the most prejudiced among the telephone and telegraph engineers that inductance coils in a transmission line do not always act as “choke coils.” Such a proof would have been worthless if it had consisted of mathematical formulas only. I needed the formulas myself for my own guidance, but watching the developments in wireless telegraphy which was born at that time I learned that full-sized apparatus and successful operation was the only proof which would appeal to the so-called practical engineer. He is like the man from Missouri who “wants to be shown,” by actual experimental performance and by nothing less. My mathematical solution of the problem of transmission over a lumpy telephone line containing inductance coils at periodically recurring points filled me with confidence; it had never been even attempted by the advocates of high inductance. They evidently had missed an important concept in the physical character of the transmission problem. The length of the wave to be transmitted was not considered and hardly ever mentioned by them, and hence their failure to recognize in it one of the fundamental elements in the study of transmission of magnetic action over such a line.