Timeline of Related Developments

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This information comes from two books:

The 'Acknowledgements' of the first book states:

This book is the accumulation of gleanings from literally hundreds of books, magazines, papers, and reports from many sources. I spent hours in the libraries of the University of Tennessee, Bryan College, Florida Institute of Technology, the city libraries of Melbourne and Orlando, Florida, and of Chattanooga and Dayton, Tennessee. Much of my information came from the libraries of the places I worked, particularly the David W. Taylor Model Basin and the Patrick Air Force Base. [...] I also want to acknowledge the aid of the Antique Wireless Association for clearing up some questionable points, and for their "Old Timers Bulletin", from which I gathered many tidbits of information.

And of the second:

[...] Unfortunately, many embassies and organizations did not reply to my inquiries, but my thanks go to those that did. Very informative replies were received from the Allen Bradley Company, Atomic Energy Commission, Bell Telephone Laboratories, British Information Services, Bureau of Standards, Denver Aerospace, Canadian Marconi Co., General Electric Co., German Embassy, Hughes Aircraft Co., Northrop Corporation, and the Zenith Radio Corporation. The following broadcast stations also responded: KCBS, WGY, WHA, WLAW, and WWJ. [...]

These books included many items not related to the overhead lines insulators were used on (such as wireless transmission, underground and submarine cables, etc), which do not pertain to what I am focusing on and thus were intentionally not included. All information which follows is excerpted from those two books.


The Status of Electricity and Magnetism Before Christ

Undoubtedly the most familiar form of electricity known to the ancients was lightning-- that terrifying flash of fire from the heavens which can kill animals and men, splinter trees, and start fires. The accompanying noise was impossible for man to duplicate. It could only be an indication of anger of the gods.

The Early Years Through the Fifteenth Century

The first fifteen centuries following the birth of Christ comprised a period more of re-discovery than of discovery. Experiments were repeated but they largely verified what was already known. Few if any major breakthroughs were made. Development in the field of electricity was negligible. The period did see magnetism come to a practical use in the form of the mariner's compass.

The Sixteenth Century (1500s)

Although the sixteenth century may be considered one of scientific awakening, the early years of the century produced little in the field of electricity. It was, however, the century of progress in the field of magnetism, due primarily to the researches of Dr. Gilbert. This century also marked the beginning of the use of instruments in the investigation of electrical and magnetic problems.

The Seventeenth Century (1600s)

It was an age when the importance of experimental investigations into the causes of electrical, magnetic, and other phenomena became evident. Men were beginning to realize that complete information on any phenomenon was not obtained solely by mental concentration and pure reasoning. [William] Gilbert had pointed out that many of the ideas of the early philosophers were not only completely erroneous, but the errors had been propagated for hundreds of years only because no one had methodically set up experiments and carefully observed the results. When this was done, much of the 'magic' and superstitions associated with electricity and magnetism were recognized as nothing but the consistent response to a given stimulus.

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The Eighteenth Century (1700s)

The eighteenth century was the age of Franklin, Cavendish, Coulomb, Galvani, and Volta. The science of electrical measurements came into being. Scientists were beginning to understand some of the characteristics of electrical force. The laws of electrical and magnetic forces were discovered, and the relationship between them was studied. Lightning was found to be electricity, and the means of protecting buildings from lightning became a reality. [...] Practical uses for electricity were being considered. The idea of using the tremendous speed of electricity for the transmission of intelligence became a passion of many electricians. Telegraph messages were transmitted over relatively short distances.

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The Nineteenth Century (1800s)

The nineteenth century opened with the invention of the battery by Volta, and developments in all branches of the electrical technology came so fast that nearly every year great advances were made. The chemical battery opened the possibility of new means of telegraphic communications. In this century the communication industry sprang up from a few relatively short-range telegraph line experiments to commercial lines spanning the continent. Telephone communication became a reality with the automatic dial system which was in use in some places. Even wireless telegrams were being accepted commercially. From the discovery of electrical rotation in a crude form, electrically driven machinery, streetcars, and automobiles were developed. From the motor developed the DC and AC generators. The AC generators and the invention of the transformers made high voltage power transmission a possibility. [...] The twentieth century dawned with some people believing that everything had been invented and no more major developments were likely.

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The Twentieth Century, First Decade (1900-1909)

The twentieth century came in with an explosion of knowledge in nearly all technical fields. This was particularly true of those fields related to electricity. At the opening of the decade, dry cells and batteries were coming into use. [...] Also by the turn of the century, the demand for power was so great in all parts of the country that new sources of power were required, and the demand for larger generators and alternators was increasing. The problem of which type of current was best, alternating or direct, had not been resolved, and the debate continued for some years, but hydroelectric plants with alternating current generators were now being installed where water sources were available. Steam turbine plants were being built with alternating outputs up to five million watts.

The installation of these high capacity plants led naturally to the problem of wider distribution to more customers. The distance to which the power could be distributed was limited for several reasons, primarily copper losses in the conductor. This could be solved by using higher voltages. But here again was a problem. High voltage transmission meant the voltages must be transformed at the power plant up to the transmission voltage, and from the high voltage to the voltage required for distribution at the other end of the line. This resulted in high losses that brought in no revenue. Again science came to the rescue, with the development of more efficient transformers with the use of silicon steel laminations for the transformer core. Again the distance of transmission could be increased. By increasing the voltage, still further distances could be covered, but this too was limited by the insulation on the poles or towers. This problem was solved by improving the types of insulators for the high voltage lines. [...]

As the demand for the telephone increased, more and more wires were put on poles with increased maintenance expense to the telephone companies. Again an advance was made, with the suggestion of the party line system. Although lacking the privacy of individual lines, the party line put the phones on farms and in city houses where it could not otherwise have been afforded. The multiplying costs of poles, insulators, and maintenance, particularly in the winter, brought the idea of underground lines into practice. The first underground long distance line was installed between New York City and Jersey City. Cables came into use rather than open wire lines, and a cable was run from Seattle, Washington to Sitka, Alaska. Almost as soon as the telegraph and telephone came into use, the idea of sending pictures by wire and wireless became the main interest of inventors in various parts of the world. By the end of the decade, pictures, although crude by today's standards, had been sent over appreciable distances.

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The Twentieth Century, Second Decade (1910-1919)

The second decade of the century was much like the first, with advances made in nearly all brances of the electrical field. A major development was the invention of the Watt hour meter. With this instrument, a power customer could be charged for the electrical power he used, rather than by the number of rooms in the house or the number of lights in the building. Prior to this, there was little incentive to turn off lights, since it did not affect the light bill. The meters soon became part of every electrical installation. [...] The trend in power transmission to the high voltage continued, with lines operating up to at least 7,000 volts and possibly higher. [...] The telephone networs continued to expand, with many independent companies becoming established. The means of getting more service from the lines already installed became important to the numerous telephone companies, and the phantom circuit was developed, followed soon by the use of carrier current, to multiply the use of the existing lines. [...] By the use of amplifiers, the telephone lines were extended to the West Coast. Development in vacuum tubes continued, and by the middle of the decade, the Bell system was using tubes with life expectancies of over 4,000 hours.

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The Twentieth Century, Third Decade (1920-1929)

During this period, alternating current had largely displaced direct current power, except for cities where DC had originally been installed, primarily for lighting purposes. [...] At the start of the decade, transmission lines were operating at or in the neighborhood of 150,000 volts. A few years later, this had been increased to 220,000 volts. Steam and hydroelectric plants were being built all over the country. The efficiency of the power plant alternators was improved by the use of hydrogen gas cooling, since hydrogen has greater heat conductivity and less drag on the rotating armature, than air. The idea of taking electricity to the farm brought a movement of farm cooperatives to bring power to those farms wanting it. [...] In the line of fixed capacitors, a major breakthrough was made with the development of the electrolytic capacitors. The paper capacitors required for filtering in B battery eliminators or in sets operating off the power line, were in general as big or bigger than the power transformers. With the development of the electrolytic capacitor, the size for a given capacity and voltage rating of the filter capacitors could be reduced on the order of 30 times.

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The Twentieth Century, Fourth Decade (1930-1939)

By this time, the electric lights, telephones, telegraphs, and radios had become accepted parts of society. [...] The middle of the decade gave birth to the 'computer age'. [...] Television, soon to become a major industry, grew from a mechanical system at the start of the decade, to an electronic system with reasonable resolution by the end of the decade. [...] In the power area, the President signed an order creating the Rural Electrification Administration and the Tennessee Valley Authority. With the organization of farmers requesting service, power was brought to millions of farms all across the country. Where suitable locations were found, dams were being constructed for both power generation and flood control. Also, the high voltage lines from Boulder Dam to Los Angeles was energized at 287,000 watts. Electric locomotives utilizing AC series motors came into use. [...] The telephone systems were still rapidly expanding, and the coaxial cable was being developed for both multi-channels, telephone, television, and the ikonophone-- a telephone system with the speaker at either end able to see the other.

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