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Opinion of the Court.

the contention of the Government, urged here and below, as to the measure of damages, with respect to which the court made no findings. The Government's contention is that the variable capacity shunt of the accused devices bridged all the inductance in the receiving antenna circuit, and that even though those devices infringed they nevertheless embody an improvement over Marconi's Claim 16, in which only the transformer coil was bridged. In computing the damages the court measured them by 65% of the cost to the Government of the induction coils which would be required to replace in the accused devices the adjustable condensers as a means of tuning, taking into account the greater convenience and efficiency of condenser tuning. The allowance of only 65% was on the theory that if the parties had negotiated for the use of the invention the price would have been less than the cost to the Government of the available alternative means of tuning.

In computing the damages the court apparently did not take into account or attempt to appraise any contribution which may have been made by the improvement over Marconi which the Government asserts was included in the accused devices. The court found that where the condenser is connected in series with the inductance coils in the antenna it “can be used to shorten the natural resonant wave length of the antenna circuit but cannot lengthen it beyond what would be the resonant wave length if the condenser were not present.” On the other hand, it found that when the condenser is connected in parallel it enables the periodicity of the antenna to be lowered, permitting the reception of longer wave-lengths.

The computation of damages was based on the premise that the advantage to the Government resulting from the infringement was derived from the ability which the accused devices had thus acquired to receive longer wavelengths. But there was substantial testimony that the ar

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rangement disclosed by Marconi's specifications was in effect a connection in series which did not make possible reception of longer wave-lengths, as did the arrangement in the accused devices. And the court nowhere found that the arrangement covered by Marconi's Claim 16 did make possible such reception. The appropriate effect to be given to this testimony is important in the light of the recognized doctrine that if a defendant has added "noninfringing and valuable improvements which had contributed to the making of the profits," it is not liable for benefits resulting from such improvements. Westinghouse Electric Co. v. Wagner Mfg. Co., 225 U. S. 604, 614–15, 616–17; Sheldon v. Metro-Goldwyn Corp., 309 U. S. 390, 402-406, and cases cited. Finding LXIII that the Government was using "apparatus coming within the terminology of Claim 16," and Finding 23 on the accounting that the accused devices "infringe Claim 16 of the Marconi patent,” give no aid in solving this problem for they are not addressed to the question whether, assuming infringement, the Government has made improvements which of themselves are non-infringing. That can only be afforded by findings which appraise the evidence, establish the scope of Marconi's claim and the nature and extent of the difference in function, if any, between the device claimed by Marconi and those used by the Government, and determine whether any differences shown to exist constitute a "non-infringing improvement" for which Marconi deserves no credit.

The judgment as to Claim 16 will be vacated and the cause remanded for further proceedings. The Fleming Patent No.803,684.

The Fleming patent, entitled: "Instrument for Converting Alternating Electric Currents into Continuous Currents” was applied for April 19, 1905, and granted on November 7, 1905 to the Marconi Company, as assignee Opinion of the Court.

of Fleming. Its specifications state that "this invention relates to certain new and useful devices for converting alternating electric currents, and especially high-frequency alternating electric currents or electric oscillations, into continuous electric currents for the purpose of making them detectable by and measurable with ordinary directcurrent instruments, such as a 'mirror-galvanometer of the usual type or any ordinary direct-current ammeter." Fleming's drawings and specifications show a combination apparatus by which alternating current impulses received through an antenna circuit containing the primary of a transformer are induced in the secondary of the transformer. To one end of the secondary coil is connected a carbon filament like that of an incandescent electric lamp, which is heated by a battery. Surrounding, but not touching the filament, is a cylinder of aluminum open at the top and bottom, which is connected with the other end of the secondary. The cylinder and filament are enclosed in an evacuated vessel such as an ordinary electric lamp bulb. An indicating instrument or galvanometer is so located in this circuit as to respond to the flow of current in it. The specifications explain the operation of this device:

"This arrangement described above operates as an electric valve and permits negative electricity to flow from the hot carbon b to the metal cylinder c, but not in the reverse direction, so that the alternations induced in the coil k by the Hertzian waves received by the aerial wire n are rectified or transformed into a more or less continuous current capable of actuating the galvanometer l by which the signals can be read.”

The specifications further state:

"... the aerial wire n may be replaced by any circuit in which there is an alternating electromotive force, whether of low frequency or of high frequency ..."

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"Hence the device may be used for rectifying either high-frequency or low-frequency alternating currents of electrical oscillations ...".

Only Claims 1 and 37 of the patent are in suit. They read as follows:

"1. The combination of a vacuous vessel, two conductors adjacent to but not touching each other in the vessel, means for heating one of the conductors, and a circuit outside the vessel connecting the two conductors.

"37. At a receiving-station in a system of wireless telegraphy employing electrical oscillations of high frequency a detector comprising a vacuous vessel, two conductors adjacent to but not touching each other in the vessel, means for heating one of the conductors, a circuit outside of the vessel connecting the two conductors, means for detecting a continuous current in the circuit, and means for impressing upon the circuit the received oscillations."

The current applied to the filament or cathode by the battery sets up a flow of electrons (negative electric charges) from the heated cathode, which are attracted to the cold plate or anode when the latter is positively charged. When an alternating current is set up in the circuit containing the cathode, anode, and secondary of the transformer, the electronic discharge from the cathode closes the circuit and permits a continuous flow of electricity through it when the phase of the current is such that the anode is positively charged, while preventing any flow of current through the tube when the anode is negatively charged. The alternating current is thus rectified so as to produce a current flowing only in one direction. See DeForest Radio Co. v. General Electric Co., 283 U. S. 664; Radio Corporation v. Radio Laboratories, 293 U.S. 1; Detrola Radio Corp. v. Hazeltine Corporation, 313 U. S. 259.

Claims 1 and 37 of the Fleming patent are identical in their structural elements. Both claim the vacuum tube, Opinion of the Court.

and the two electrodes connected by a circuit outside the tube, one element being heated. The claims differ only in that Claim 37 includes "means for detecting" the continuous or direct current in the anode-cathode circuit, and "means for impressing upon the circuit the received oscillations" from the transformer coil of the antenna circuit.

In the patent as originally issued there had been another difference between the two claims. Claim 37 describes the tube as being used “in a system of wireless telegraphy employing electrical oscillations of high frequency.” No such limitation was placed on Claim 1 as originally claimed, and the specifications already quoted plainly contemplated the use of the claimed device with low as well as high frequency currents. This distinction was eliminated by a disclaimer filed by the Marconi Company November 17, 1915, restricting the combination of the elements of Claim 1 to a use "in connection with high frequency alternating electric currents or electric oscillations of the order employed in Hertzian wave transmission,” and deleting certain references to low frequencies in the specifications. The result of the disclaimer was to limit both claims to the use of the patented device for rectifying high frequency alternating waves or currents such as were employed in wireless telegraphy.

The earliest date asserted for Fleming's invention, as limited by the disclaimer, is November 16, 1904. Twenty years before, on October 21, 1884, Edison had secured United States Patent No. 307,031. In his specifications he stated:

"I have discovered that if a conducting substance is interposed anywhere in the vacuous space within the globe of an incandescent electric lamp, and said conducting substance is connected outside of the lamp with one terminal, preferably the positive one, of the incandescent conductor, a portion of the current will, when the lamp is in opera

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