First Demonstration of Transatlantic Radiotelephony Summary

  • Last updated on November 10, 2022

Communications technology was advanced significantly by the work of telephone engineers who sent radio messages from the United States to Europe for the first time.

Summary of Event

The idea of commercial transatlantic communication was first raised by Guglielmo Marconi, Marconi, Guglielmo the pioneer of wireless telegraphy. Marconi used a spark transmitter to generate radio waves, which were interrupted, or modulated, to form the dots and dashes of Morse code. The rapid generation of sparks created an electromagnetic disturbance that sent radio waves of different frequencies into the air—a broad, noisy transmission that was difficult to tune and detect. The inventor Reginald Aubrey Fessenden produced an alternative method that became the basis of radio technology in the twentieth century. His continuous radio wave kept to one frequency, making it much easier to detect at long distances. Furthermore, the continuous waves could be modulated by an audio signal, making it possible to transmit the sound of speech. Radio;technological development Communications;radio Radiotelephony;transatlantic [kw]First Demonstration of Transatlantic Radiotelephony (Oct. 21, 1915) [kw]Transatlantic Radiotelephony, First Demonstration of (Oct. 21, 1915) [kw]Radiotelephony, First Demonstration of Transatlantic (Oct. 21, 1915) Radio;technological development Communications;radio Radiotelephony;transatlantic [g]France;Oct. 21, 1915: First Demonstration of Transatlantic Radiotelephony[03860] [g]United States;Oct. 21, 1915: First Demonstration of Transatlantic Radiotelephony[03860] [c]Science and technology;Oct. 21, 1915: First Demonstration of Transatlantic Radiotelephony[03860] [c]Communications and media;Oct. 21, 1915: First Demonstration of Transatlantic Radiotelephony[03860] [c]Radio and television;Oct. 21, 1915: First Demonstration of Transatlantic Radiotelephony[03860] Fessenden, Reginald Aubrey De Forest, Lee Arnold, Harold D. Carty, John J. Vail, Theodore Newton

Lee de Forest sends a message using radiotelephony.

(Library of Congress)

Fessenden was faced with the problem of generating continuous waves. He found the answer in the alternator that produced electric current for use in the home and workplace. Fessenden’s alternator was designed to generate electromagnetic waves at the high frequencies required in radio transmission. It was specially constructed at the laboratories of the General Electric Company General Electric Company and shipped to Brant Rock, Massachusetts, in 1906 for testing. Radio messages were sent to a boat cruising offshore, and the feasibility of radiotelephony was thus demonstrated. Fessenden followed this success with a broadcast of messages and music between Brant Rock and a receiving station constructed at Plymouth, Massachusetts.

The equipment installed at Brant Rock had a range of about 99 miles (160 kilometers). The transmission distance was determined by the strength of the electric power delivered by the alternator, which was measured in watts. Fessenden’s alternator was rated at 500 watts, but it usually delivered much less. This was sufficient, however, to send a radio message across the Atlantic. Fessenden had built a receiving station at Machrihanish, on the west coast of Scotland, to test the operation of a large rotary spark transmitter he had constructed. An operator at this station picked up the voice of an engineer at Brant Rock who was sending instructions to Plymouth. The first radiotelephone message had been sent across the Atlantic by accident.

Fessenden decided not to make this startling development public. The station at Machrihanish was destroyed in a storm, making it impossible to carry out further tests. The successful transmission undoubtedly had been the result of exceptionally clear atmospheric conditions that might never again favor the inventor. Fessenden decided to concentrate on perfecting and marketing a system of radiotelephony that would join ships at sea with stations on the shore. He set up companies to exploit his invention and continued experiments with radio wave generation.

One of the parties following the experiments in radiotelephony was the American Telephone and Telegraph Company American Telephone and Telegraph (AT&T). Fessenden entered into negotiations to sell his system to AT&T, but the sale was never made, as the company was more interested in finding a way of improving its wired communications than branching out into radio.

The strategy followed by AT&T president Theodore Newton Vail was to dominate telephone communication in the United States with one integrated system and one universal service. This ambitious plan required control of all technologies related to long-distance communication. Subsequently, AT&T consolidated its research and development effort into a department led by John J. Carty, formerly chief engineer of the New York Telephone Company. After the financial panic of 1907 had been overcome, Carty was given the resources and scientific personnel to initiate a program of impressive technical development of the telephone system. His laboratory became one of the leading industrial research organizations in the United States.

The technical problem facing Carty was to extend the reach of long-distance telephone service. Vail’s strategy of one system was based on transcontinental service, and Carty had promised a demonstration of a coast-to-coast telephone call for the Panama-Pacific International Exposition Panama-Pacific International Exposition[Panama Pacific International Exposition] scheduled for 1914. Carty’s laboratory searched for a means to amplify telephone messages so that they could travel longer distances. After examining magnetic and electromechanical devices, Carty’s research staff decided that electronic amplification promised better results. This led them to examine the newly developed vacuum tube. Vacuum tubes

The English physicist John Ambrose Fleming invented a two-element (diode) vacuum tube in 1904 that could be used to generate and detect radio waves. Two years later, the American inventor Lee de Forest added a third element to the diode to produce his “audion” Audions (triode), which was a more sensitive detector. Announcements of this progress in radio technology had made the stockholders of the telephone companies fear that wired communications soon might be replaced completely by radio. AT&T wanted to gain a foothold in radio in case rapid technical advances made it a better form of communication than the telephone.

The AT&T research laboratory had carefully examined the new devices produced for radio. Carty became convinced that the amplification problem in both telephony and radio had the same solution. An electronic amplifier could be used to increase the strength of telephone signals, and it could generate continuous radio waves that could travel long distances. On Carty’s advice, AT&T purchased the rights to de Forest’s audion. A team of about twenty-five researchers, under the leadership of physicist Harold D. Arnold, undertook the job of perfecting the triode and turning it into a reliable amplifier. The improved triode was responsible for the success of transcontinental telephone service introduced in January, 1915. Also, the triode was the basis of AT&T’s foray into radiotelephony.

Carty’s research plan called for a system composed of an oscillator (to generate the carrier wave), a modulator (to impose the audio signal on the carrier), and an amplifier (to transmit the modulated carrier wave through the air). Arnold designed the power amplifier around banks of triodes arranged in parallel. The test transmitter constructed in 1915 consisted of a modulator and a three-hundred-tube parallel amplifier. As each tube gave out 25 watts, the total power output of the transmitter was 7,500 watts, enough to send the radio waves over thousands of kilometers.

The apparatus was installed in the U.S. Navy’s radio tower in Arlington, Virginia, in 1915. Radio messages from Arlington were picked up at a receiving station in California, a distance of 2,485 miles (4,000 kilometers), then at a station in Pearl Harbor, Hawaii, which was 4,474 miles (7,200 kilometers) from Arlington. AT&T’s engineers had succeeded in joining its telephone lines with the radio transmitter at Arlington; therefore, president Vail could pick up his telephone and talk directly with someone in California.

The next experiment was to send a radio message from Arlington to a receiving station set up in the Eiffel Tower in Paris. After several unsuccessful attempts, the telephone engineers in the Eiffel Tower finally heard Arlington’s messages on October 21, 1915. The AT&T receiving station in Hawaii also picked up the messages. The acknowledgments of receipt of the messages had to be sent by telegraph to the United States because both stations were set up to receive only. The Arlington-to-Paris transmission was a one-way transmission; two-way radio communication was still years in the future.


The announcement that messages had been received in Paris was front-page news that brought about an outburst of national pride in the United States. The demonstration of transatlantic radiotelephony was more important as publicity for AT&T than as a scientific advance. The national attention and media response were fixed firmly on the Arlington-to-Paris transmission, despite the fact that the Arlington-to-Hawaii transmission was longer and involved the more difficult task of sending radio waves across land. The great publicity given to the receipt of messages in France achieved AT&T’s goal of taking the high ground of radio technology and imprinting this fact on the public mind. Telephone stockholders would not concern themselves any longer with the threat that radio posed to wired communication. AT&T announced a transcontinental radiotelephone service in 1915, although it had no intention of replacing its wires; radio was to complement the universal service.

Vail ensured that all the credit went to AT&T and to Carty’s laboratory. Both Fessenden and de Forest attempted to draw attention to their contributions to long-distance radiotelephony, but to no avail. The Arlington-to-Paris transmission was a triumph for corporate public relations and corporate research. The development of the triode had been achieved with large teams of highly trained scientists—a contrast to the small-scale efforts of Fessenden and de Forest, who had little formal scientific training. Carty’s laboratory was an example of the new type of industrial research that was to dominate the twentieth century. The golden days of the lone inventor, in the mold of Thomas Alva Edison or Alexander Graham Bell, were gone. Only large corporations had the resources to develop new technology and market it. It was significant that all the businesses started by Fessenden and de Forest failed. The pioneers of radio received little financial reward for their efforts.

In the years that followed the first transatlantic radiotelephone messages, AT&T did little to advance the technology or to develop a commercial service. The equipment used in the 1915 demonstration was more a makeshift laboratory apparatus than a prototype for a new radio technology. The messages sent were short and faint. There was a great gulf between hearing “hello” and “good-bye” amid the static and the setting up of reliable and affordable communication. Subsequently, the many predictions of a direct telephone connection between New York and other major cities overseas were premature. It was not until 1927 that a transatlantic radio circuit was opened for public use. By that time, a new technological direction had been taken, and the method used in 1915 had been superseded by shortwave radio communication. Radio;technological development Communications;radio Radiotelephony;transatlantic

Further Reading
  • citation-type="booksimple"

    xlink:type="simple">Aitken, Hugh G. J. The Continuous Wave: Technology and American Radio 1900-1932. Princeton, N.J.: Princeton University Press, 1985. Authoritative work on the development of radio technology written by the leading scholar in the field. Following on his Syntony and Spark (see below), Aitken provides a detailed and comprehensive account of the technology and the business affairs of radio.
  • citation-type="booksimple"

    xlink:type="simple">_______. Syntony and Spark: The Origins of Radio. New York: John Wiley & Sons, 1976. A good history of the early development of radio from the discovery of radio waves to the work of Marconi. Includes many diagrams of early radio apparatuses.
  • citation-type="booksimple"

    xlink:type="simple">Brooks, John. Telephone: The First Hundred Years. New York: Harper & Row, 1976. Popular account of the growth of the communications industry. Provides clear technical explanations for the general reader. Useful for putting technical events into a broader context.
  • citation-type="booksimple"

    xlink:type="simple">De Forest, Lee. Father of Radio: The Autobiography of Lee de Forest. Chicago: Wilcox & Follett, 1950. Firsthand account of the early years of radio provides many insights into the interaction of business and technology. As the author is highly biased, only his version of the events is described.
  • citation-type="booksimple"

    xlink:type="simple">Fagen, M. D., ed. A History of Science and Engineering in the Bell System: The Early Years, 1875-1925. Murray Hill, N.J.: Bell Telephone Laboratories, 1975. The official history of the work carried out by the AT&T laboratories. Chapters are arranged by topic. “The Advent of Radio” describes the development of this technology in detail.
  • citation-type="booksimple"

    xlink:type="simple">Head, Sydney W., Thomas Spann, and Michael A. McGregor. Broadcasting in America: A Survey of Electronic Media. 9th ed. Boston: Houghton Mifflin, 2000. The standard introduction to the institutions of radio and television in the United States. Begins with an analysis of the invention of wireless radio broadcasting.
  • citation-type="booksimple"

    xlink:type="simple">Hong, Sungook. Wireless: From Marconi’s Black-Box to the Audion. Cambridge, Mass.: MIT Press, 2001. Draws on previously untapped archival evidence and recent work in the history of technology to provide a new perspective on the early days of wireless communication. Concludes with a discussion of Lee de Forest’s audion and the shift from wireless telegraphy to radio.
  • citation-type="booksimple"

    xlink:type="simple">Reich, Leonard S. The Making of American Industrial Research: Science and Business at GE and Bell, 1876-1926. Cambridge, England: Cambridge University Press, 1985. Concentrates on the operation of industrial research and the business strategy that lay behind it. Gives a detailed analysis of the work done by Carty and Arnold in the AT&T laboratory.

First Transatlantic Telegraphic Radio Transmission

Fessenden Pioneers Radio Broadcasting

Principles of Shortwave Radio Communication Are Discovered

Radio Develops as a Mass Broadcast Medium

Radio Broadcasting Begins

National Broadcasting Company Is Founded

Categories: History