Tag Archives: American Telephone and Telegraph

Patent Application…


As can be imagined, there are quite a number of patents to be found within this collection. In addition to Armstrong’s patents, a variety of patents issued to other individuals can be found as well.

Armstrong was issued five patents on December 26, 1933. The first is patent number 1,941,066 titled: "Radio Signaling System," the second is patent 1,941,067:"Radio Broadcasting and Receiving," the third is patent 1,941,068:  "Radiosignaling," the fourth is patent 1,941,069:  "Radiosignaling" (specifically dealing with noise suppression), and the last is patent 1,941,447:  "Radio Telephone Signaling."

I came upon a patent application that appears to have been "dropped". You will see in the documents I have posted here that Armstrong filed for a patent for improvements in "Radio Signaling," through his attorneys Moses & Nolte, on March 26, 1931.

Application for Patent. Armstrong. Radio Signaling. 1931 March 26

Armstrong’s attorney requested an amendment from Armstrong based on an "office action" from the U.S. Patent Office, where they cite patent number 1,797,317. Patent number 1,797,317, titled "Binaural Phase-Discrimination Radio System," was granted on March 24, 1931 to Smart Brand and Pierre Mertz, assignors to American Telephone and Telegraph Company.

Request for Amendment.Radio Signaling. 1932 April 27

Armstrong’s written disclosure (first four pages) for this patent application, along with accompanying figures, can be seen below.

Armstrong.Disclosure Draft.1930 April 21.Page 1


Armstrong.Disclosure Draft.1930 April 21.Page 2












Armstrong.Disclosure Draft.1930 April 21.Page 3




Armstrong.Disclosure Draft.1930 April 21.Page 4











Armstrong.Disclosure Draft. Figure I.1930 August 21



Armstrong.Disclosure Draft. Figure II.1930 August 21











 Instead of making the amendment as requested by his attorney, Armstrong decided to let the application drop.  From reading Armstrong’s patents listed earlier, I can not tell if this dropped application was rewritten into alternate Armstrong patent. Perhaps someone can shed some light on this?

The Superheterodyne

When the United States entered World War I, Armstrong enlisted in the Signal Corps. In 1917 he was posted to France, placed in charge of the Radio Group of the Research Section of the Division of Research and Inspection. This Division had been created in order to examine any existing equipment manufactured by the Europeans for the American Expeditionary Forces.                                              

Round, Henry Joseph, 1960

The Major set off to France but en route he was delayed in England due to heavy fog. While there, he ventured to London, stopping by the Marconi offices. The letter seen here (below), dated 1917 October 28, from Armstrong to his mother, details his visit and recounts his introduction with Henry Joseph Round.

EHA letter to Mother, 1917 October 28, first 2 pages



EHA letter to Mother, 1917 October 28, last 2 pages



Round was an engineer with Marconi who, at the time, was in charge of the Admiralty’s wireless direction-finding stations. It was here that Armstrong was introduced to Round’s short-wave equipment. Round had created these amplifiers by designing his own vacuum tube (V24). These tubes were not, and would never be, available to the French and the Americans, as these tubes were not appropriate for the task. Armstrong’s attention was captured as this was a problem that required further research. 

 Armstrong had studied heterodyne circuitry for quite a while and understood it well. This meeting with Round pushed him further and he continued to examine the problem of receiving weak high frequency signals. As the Major recounts some years later upon receiving the Edison Medal in 1943:

"The third link came months later as I happened to be watching a night bombing raid and wondered at the ineffectiveness of the antiaircraft fire. I may say that night bombing was not very dangerous in those days, either for the man on the ground or the man in the airplane. Thinking of some way of improving the methods of locating the position of airplanes, I conceived the idea that perhaps very short waves sent out from them by the motor ignition systems might be used. The unique nature of the problem, involving the amplification of waves shorter than any ever contemplated and quite insoluble by any conventional means of reception, demanded a radical solution. All three links of the chain suddenly joined up and the superheterodyne method of amplification was practically forced into existence. Not one link in the chain could have been dispensed with. This, I think is the only completely synthetic invention I have ever made." 1

The bombing raid and third link, to which Armstrong refers above, occurred in Paris, March 1918. He had thus sorted out how to use the heterodyne principle to bring short-wave frequencies down to the range of his long-wave amplifier. He worked out the necessary experiments needed to prove his forthcoming invention, writing down the proposed method in June 1918 with Major Buckley signing off as witness (proposal seen here in 3 pages).

Method of Reception, Disclosed to Major O.E. Buckley, 1918 May-June, page 1


Method of Reception, Disclosed to Major O.E. Buckley, 1918 May-June, page 2










Method of Reception, Disclosed to Major O.E. Buckley, 1918 May-June, page 3

Following Armstrong’s proposed methodology to Major Buckley, experiments would need to be conducted. Armstrong needed assistance to stage these experiments and create the necessary apparatus. With war work taking precedence and his fellow officers tied up in other pressing projects, his work was delayed. The first model was not ready until November. Armstrong first applied for patent in France in December 1918 and for United States patent in February 1919.

When Armstrong returned from the war he presented his paper, "A New System of Short Wave Amplification," to the Institute of Radio Engineers in December of 1919, delineating his new receiver.

In 1920, Westinghouse purchased Armstrong’s regeneration and superheterodyne patents. Also, around this time, AT & T purchased Lucien Levy’s patent for essentially, the same invention. Originally Levy’s patent covered a different purpose than did Armstrong’s resulting in the US Patent Office not catching the conflict. Someone eventually noticed this apparent conflict and priority needed to be resolved.

The Court of Appeals in the District of Columbia ruled in Levy’s favor and his patent was issued on November 5, 1929, with a priority date of August 4, 1917 (he had filed 6 months prior to Armstrong). While Levy, by law, is considered the inventor of the superheterodyne method, Armstrong is recognized as bringing about its commercialization through the single tuning knob superhet receiver.



1-Armstrong, Edwin H. "Vagaries and Elusiveness of Invention," Electrical Engineering 62 (April 1943).

Additional Information regarding superheterodyne patent:

Schottky, Walter  "On the Origin of the Super-Heterodyne Method," Proceedings if the IRE, Vol. 14, No. 5, 695-698 (October 1926)

Armstrong, Edwin H. "A New System of Short Wave Amplification," Proceedings of the IRE, Vol. 9, No. 1, 3-27 (February 1921)

Douglas, Alan S. "Who Invented the Superheterodyne?," Proceedings of the Radio Club of America, Inc., Vol. 64, No. 3, 123-142 (November 1990)