Opinion of the Court. 320 U.S. (b), on petition of the Marconi Company in No. 369, to review the judgment of the Court of Claims holding invalid the claims in suit, other than Claim 16, of the Marconi patent, and holding the Fleming patent invalid and not infringed, and on petition of the Government in No. 373, to review the decision allowing recovery for infringement of Claim 16 of the Marconi patent. No review was sought by either party of so much of the court's judgment as sustained the Lodge patent and held the first Marconi reissue patent not infringed. Marconi Patent No. 763,772. This patent, granted June 28, 1904, on an application filed November 10, 1900, and assigned to the Marconi Company on March 6, 1905,1 is for improvements in apparatus for wireless telegraphy by means of Hertzian oscillations or electrical waves. In wireless telegraphy, signals given by means of controlled electrical pulsations are transmitted through the ether by means of the socalled Hertzian or radio waves. Hertzian waves are electrical oscillations which travel with the speed of light and have varying wave lengths and consequent frequencies intermediate between the frequency ranges of light and sound waves. The transmitting apparatus used for sending the signals is capable, when actuated by a telegraph key or other signalling device, of producing, for short periods of variable lengths, electrical oscillations of radio frequency (over 10,000 cycles per second) in an antenna or open circuit from which the oscillations are radiated to a distant receiving apparatus. The receiver has an open antenna circuit which is electrically responsive 1 On November 20, 1919, the Marconi Company assigned to the Radio Corporation of America all of its assets, including the patents here in suit, but reserved, and agreed to prosecute, the present claims against the United States, on which it had instituted suit on July 29, 1 Opinion of the Court. to the transmitted waves and is capable of using those responses to actuate by means of a relay or amplifier any convenient form of signalling apparatus for making audible an electrically transmitted signal, such as a telegraph sounder or a loud speaker. In brief, signals at the transmitter are utilized to control high frequency electrical oscillations which are radiated by an antenna through the ether to the distant receiver and there produce an audible or visible signal. All of these were familiar devices at the time of Marconi's application for the patent now in suit. By that time radio had passed from the theoretical to the practical and commercially successful. Four years before, Marconi had applied for his original and basic patent, which was granted as No. 586,193, July 13, 1897 and reissued June 4, 1901 as reissue No. 11,913. He applied for his corresponding British patent, No. 12039 of 1896, on June 2, 1896. Marconi's original patent showed a two-circuit system, in which the high frequency oscillations originated in the transmitter antenna circuit and the detecting device was connected directly in the receiver antenna circuit. Between 1896 and 1900 he demonstrated on numerous occasions the practical success of his apparatus, attaining successful transmission at distances of 70 and 80 miles. During those years he applied for a large number of patents in this and other countries for improvements on his system of radio communication.2 2 See Marconi Wireless Tel. Co. v. National Electric Signalling Co., 213 F. 815, 825, 829-31; Encyclopedia Britannica (14th Ed.) vol. 14, p. 869; Dunlap, Marconi, The Man and His Wireless; Jacot and Collier, Marconi-Master of Space; Vyvyan, Wireless Over Thirty Years; Fleming, Electric Wave Telegraphy, 426-443. Marconi was granted eight other United States patents for wireless apparatus on applications filed between the filing dates of Nos. 586,193 and 763,772. They are Nos. 624,516, 627,650, 647,007, 647,008, 647,009, 650,109, 650,110, 668,315. Opinion of the Court. 320 U.S. The particular advance said to have been achieved by the Marconi patent with which we are here concerned was the use of two high frequency circuits in the transmitter and two in the receiver, all four so adjusted as to be resonant to the same frequency or multiples of it. The circuits are so constructed that the electrical impulses in the antenna circuit of the transmitter vibrate longer with the application to the transmitter of a given amount of electrical energy than had been the case in the previous structures known to the art, and the selectivity and sensitivity of the receiver is likewise enhanced. Thus increased efficiency in the transmission and reception of signals is obtained. The specifications of the Marconi patent state that its object is "to increase the efficiency of the system and to provide new and simple means whereby oscillations of electrical waves from a transmitting station may be localized when desired at any one selected receiving station or stations out of a group of several receiving-stations." The specifications describe an arrangement of four high frequency circuits tuned to one another-two at the sending station associated with a source of low frequency oscillations, and two at the receiving station associated with a relay or amplifier operating a signalling device. At the sending station there is an open antenna circuit which is "a good radiator," connected with the secondary coil of a transformer, and through it inductively coupled with a closed circuit, which is connected with the primary coil of the transformer, this closed circuit being a "persistent oscillator." At the receiving station there is an open antenna circuit constituting a "good absorber" inductively coupled with a closed circuit capable of accumulating the received oscillations. The patent, in describing the arrangement of the apparatus so as to secure the desired resonance or tuning, specifies: "The capacity and self-induction of the four 1 Opinion of the Court. circuits-i. e., the primary and secondary circuits at the transmitting-station and the primary and secondary circuits at any one of the receiving-stations in a communicating system are each and all to be so independently adjusted as to make the product of the self-induction multiplied by the capacity the same in each case or multiples of each other-that is to say, the electrical time periods of the four circuits are to be the same or octaves of each other." And again, "In employing this invention to localize the transmission of intelligence at one of several receiving-stations the time period of the circuits at each of the receiving-stations is so arranged as to be different from those of the other stations. If the time periods of the circuits of the transmitting-station are varied until they are in resonance with those of one of the receivingstations, that one alone of all the receiving-stations will respond, provided that the distance between the transmitting and receiving stations is not too small." The drawings and specifications show a closed circuit at the transmitting station connected with the primary 3 Capacity is the property of an electrical circuit which enables it to receive and store an electrical charge when a voltage is applied to it, and to release that charge as the applied voltage is withdrawn, thereby causing a current to flow in the circuit. Although any conductor of electricity has capacity to some degree, that property is substantially enhanced in a circuit by the use of a condenser, consisting of two or more metal plates separated by a non-conductor, such that when a voltage is applied to the circuit one plate will become positively and the other negatively charged. Self-inductance is the property of a circuit by which, when the amount or direction of the current passing through it is changed, the magnetic stresses created induce a voltage opposed to the change. Although any conductor has self-inductance to some degree, that property is most marked in a coil. See generally Albert, Electrical Fundamentals of Communication, Chs. V, VI, VII, and IX; Terman, Radio Engineering, Chs. II and III; Morecroft, Principles of Radio Communication, Chs. I, II, III; Lauer and Brown, Radio Engineering Principles, Chs. I and II. Opinion of the Court. 320 U.S. of an induction coil, and embracing a source of electrical current and a circuit-closing key or other signalling device. The secondary of the induction coil is connected in a circuit which includes a spark gap or other producer of high frequency oscillations and, in a shunt around the spark gap, the primary coil of an oscillation transformer and a condenser, preferably so arranged that its capacity can readily be varied. This shunt circuit constitutes one of the two tuned circuits of the transmitter, and is often referred to as the closed or charging circuit. The secondary coil of the transformer is connected in the open or antenna circuit, one end of which is connected with the earth, the other to a vertical wire antenna or an elevated plate. This antenna circuit also includes an induction coil, preferably one whose inductance is readily variable, located between the antenna or plate and the transformer. The receiver consists of a similar antenna circuit connected with the primary coil of a transformer, and having a variable induction coil located between the antenna or plate and the transformer. A shunt circuit bridging the transformer and containing a condenser which is preferably adjustable may also be added. The secondary coil of the transformer is connected through one or more interposed inductance coils, "preferably of variable inductance," with the terminals of a coherer or other suitable detector of electrical oscillations. The closed receiver circuit also contained one or more condensers. 4 A coherer was a device disclosed by Branly as early as 1891. It was used by Lodge in experiments described in the London Electrician for June 15, 1894, p. 189, and was in common use thereafter as a detector of radio waves until replaced by the crystal and the cathodeanode tube. The most common form consisted of a tube containing metal filings which, in their normal state, were a non-conductor. When placed in a circuit through which high frequency oscillations passed, the filings aligned themselves in a continuous stream through which the low frequency electrical current operating a key or other |