Radio Corporation of America v. EJ Edmond & Co.

• Decision Date: 11 July 1927
• Citation: 20 F.2d 929
• Parties: RADIO CORPORATION OF AMERICA et al. v. E. J. EDMOND & CO., Inc.
• Court: U.S. District Court — Southern District of New York

20 F.2d 929 (1927)

RADIO CORPORATION OF AMERICA et al. v. E. J. EDMOND & CO., Inc.

District Court, S. D. New York.

July 11, 1927.

Sheffield & Betts, of New York City (Charles Neave, Stephen H. Philbin, and Abel E. Blackmar, all of New York City, and Harry E. Dunham, of Schenectady, N. Y., of counsel), for plaintiffs.

Miller, Otis, Farr & Henderson, of New York City (C. D. Ehret, of Philadelphia, Pa., George F. Scull, of New York City, Paxson Deeter, of Philadelphia, Pa., and H. B. Farr, of New York City, of counsel), for defendant.

THACHER, District Judge.

The patent and claims in suit were held valid and infringed in Radio Corporation et al. v. Splitdorf Electric Co., 14 F.(2d) 643, by Bodine, District Judge, whose conclusion finds strong support in the thoroughly well considered opinion of MacLean, J., of the Exchequer Court of Canada, in Canadian General Electric Co., Ltd., v. Fada Radio, Ltd., decided April 14, 1927, where Alexanderson's Canadian patent, No. 208,583, covering the same invention, was held valid and infringed.

The patent relates to radio receiving apparatus, and particularly to a system for the selection of oscillations of a given wave length from mixed oscillations. The problem of selecting oscillations of a given wave length from the confusion of oscillating currents affecting the antenna of radio receiving apparatus had long been known in the prior art of radio reception. The Stone patent, No. 714,756, of December 2, 1902, and the Marconi-Franklin British patent, No. 12,960, dated December 23, 1907, disclose tuned circuits inductively coupled, arranged in cascade to obtain selectivity. Stone and Marconi attained high degrees of selectivity through the use of successive tuned circuits, each of which to a degree screened out the interfering oscillations with which they were not in resonance, and passed on the desired oscillations with which they were in resonance. Selectivity in such circuits was, however, dependent upon loose inductive coupling between the successive circuits, and with loose coupling the strength of the desired signal was greatly diminished. If close coupling was employed to increase the signal strength, the undesired oscillations were carried from one circuit to another and the system ceased to be selective. Thus in Stone and Marconi it was extremely difficult, if not impossible, to detect the weak signals of fardistant stations, when the antenna was affected by the interference of powerful nearby stations.

In the fall of 1912, Alexanderson first learned of the De Forest audion from Hammond. Immediately the thought occurred to him that it might be used as a relay for radio frequency currents in a series of tuned circuits. It was his conception that by a series of tuned circuits, connected by suitable relays, which would effectively impress upon the succeeding circuit the selected oscillations of the preceding circuit, a very high degree of selectivity could be attained without loss of signal strength. This conception may have occurred to others, but, whether it did or not, Alexanderson was the first to use the audion as a relay for this purpose. That this was invention I have no doubt. When Alexanderson told Hammond of his intention to try the audion as a relay of radio frequency oscillations connecting tuned circuits, Hammond said he believed the audion was too sluggish for this purpose; but Alexanderson and the engineers of the General Electric Company working under his supervision constructed a series of resonant circuits connected by audions as relays, and attained, without loss of signal strength, a greater degree of selectivity than had theretofore been possible. The audion was known in the art as early as February, 1908, and the fact that no one had used it for this purpose prior to Alexanderson is persuasive evidence of invention.

That the prior art does not disclose anticipation of Alexanderson's invention is very clearly shown in the Splitdorf and Fada Cases, cited supra. Indeed, the only references claimed to be in anticipation of Alexanderson which are discussed in the defendant's brief are Schloemilch and Von Bronk, patent No. 1,087,892, and Armstrong, patent No. 1,113,149. I find in the disclosure of Schloemilch and Von Bronk nothing which can be said to advance the art of selectivity in radio receivers or anticipate Alexanderson. The purpose of this invention was to amplify radio frequency currents, and nothing is said about selecting desired signals, or excluding interfering signals. In one of the patent drawings there is shown a tuned antenna circuit coupled by induction with the grid circuit of an audion amplifier, the plate circuit of which is in turn coupled by induction with a detector circuit. Neither the grid nor the plate circuit of the audion is tuned. Connected with the detector circuit, an intermediate tuned circuit is shown. There is no association of successively tuned circuits connected by relays, and all that is said of the tuned circuit which is associated with the detector is: "An intermediate circuit N syntonized to the oscillations will preferably be provided." For what purpose is not stated. No doubt because it was well known that a circuit tuned to resonance of a desired signal would exclude interfering signals to some extent. This casual reference is not shown to have any relevance to the disclosure. Apparently it was merely a mechanical suggestion for the insertion in the receiving instrument of a tuned circuit, so that the system might be given some slight measure of selectivity by the insertion of a means to that end which was well known in the art. It was certainly not a disclosure or anticipation of Alexanderson's arrangement of successive circuits, all tuned to the same frequency and linked together by relays. The precise date of Alexanderson's invention becomes unimportant, and need not be considered, because the invention of Schloemilch and Von Bronk, even if prior in time, does not anticipate the invention of Alexanderson.

In Armstrong's feed back audion circuit, patent No. 1,113,149, to which priority of invention is conceded, selectivity is attained by regeneration. Prior to his invention the presence of radio frequency oscillations in the plate or wing circuit of an audion used only as a detector was not suspected. Armstrong tuned the plate circuit of an audion detector to radio frequency in resonance with the grid circuit, and through his feed back connection between the two circuits found that he could feed back from the plate circuit into the grid circuit radio frequency oscillations of the same frequency as that of the desired incoming signal, and thus obtain marked amplification of the desired signal. Armstrong v. De Forest Radio Tel. & Tel. Co. (C. C. A.) 280 F. 584, 587-588. Armstrong, who was a witness for the defendant, testified that the regenerative selectivity attainable in his feed back circuit is due to the fact that energy is fed back from the plate circuit to the...