Appeal from the District Court of the United States for the Western District of New York.
Before MANTON, SWAN, and CHASE, Circuit Judges.
These appeals by both plaintiffs and defendant involve an infringement of five patents. The American Telephone & Telegraph Company owns the patents; the Western Electric Company, Inc., a subsidiary of the owning company, manufactures under the patents; the Electrical Research Products, Inc., a wholly owned talking motion picture subsidiary of the Western Electric Company, and the Western Electric Company, are exclusive licensees and proper parties plaintiffs. Western Electric Co. v. Pacent Reproducer Corp'n, 42 F.2d 116 (C.C.A. 2). The defendant is an exhibitor of sound pictures, and owns a theater in Buffalo, N.Y.
The patents relate to sound transmission and communication, particularly as now found in the development and reproduction of sound pictures. In improving its telephone service on transcontinental lines, the American Telephone & Telegraph Company used amplifiers, or repeaters, as they are sometimes termed, and met its best success by greatly improving the De Forest three-electrode vacuum tube. De Forest had added the third element or grid to the Fleming valve in 1906, and had used that device to some extent as a detector of radio waves; he had made little progress with it as an amplifier prior to 1912. The problem of amplification was to reproduce without distortion the input of the amplifier in its output, greatly increased in energy. Speech has been found to be extremely complicated; each of the ordinary sounds being composed of many frequencies which must be accurately reproduced. The range of audible frequencies is from 16 to 16,000 vibrations per second. For sound pictures and public address systems, substantially from 30 to 5,000 cycles must be reproduced without distortion in order to give the high quality which is known to-day. Greater power is needed to drive the loud speakers of these systems than is required for radio or telephone. The lack of faithful reproduction would be so accentuated under certain conditions as to destroy the utility of the systems. The success of sound pictures was due solely to high quality reproduction; that is, without distortions.
Each of the patents in suit relates to circuits in which the three-electrode vacuum tube is used. It is claimed that all of the inventions may be used to advantage in a single amplifier in which the final output contains the integrated result and combined advantages of all the inventions.
The Lowenstein patent, No. 1,231,764, for a telephone relay, was filed April 24, 1912, and issued July 3, 1917. Claims 1, 2, 4, 5, 6, and 7 are relied upon, and claims 1 and 7 have been selected as typical. The court below found this patent invalid.
This invention consisted essentially in the discovery that, if the grid of a vacuum tube amplifier is made to operate by potential and not by current, the distortion produced in the input circuit by current (and reproduced in amplified form in the output circuit) could be prevented, and that this restriction to potential operation could be attained by the application to the grid of a suitable initial negative potential on which the signals to be amplified are superposed.
Lowenstein disclosed a telephone system connected to a vacuum tube amplifier by a transformer 12-13. One terminal of the transformer 13 is connected to the grid 18, of the vacuum tube and the other terminal to a battery 21. This is the input circuit. The telephone receiver 24 is connected to the vacuum tube by the transformer 22-23. The transformer is connected to the plate 17 and to the battery 21. This is the output circuit. The filament 16 of the vacuum tube is heated by the battery 19, and the temperature of the filament is adjusted by a resistance 20. The battery 19 is called the "A battery." The battery which supplies current for the plate circuit is called the "B battery." The invention claimed for Lowenstein is that he inserted a third battery in the grid circuit and connected its negative terminal to the grid in order to make the grid at all times more negative than any part of the filament. This prevents the grid from becoming positive and causing current to flow in the grid circuit. This negative potential, applied to the grid by the C battery had to be greater than the most positive signal voltage that would be impressed on the grid. The negative potential applied to the grid by the C battery had also to be maintained more negative than the potential of any part of the filament. If the grid were more positive than any part of the filament, it would still compete with the plate by attracting some of the electrons which should pass to the plate, and would thus fail to prevent the flow of current and harmful consumption of energy in the external or grid circuit.
The reason for its use is stated in an article by the defendant's expert Bowles in Popular Radio, published before this controversy arose, in which he said: "Much distortion is introduced when the grid of a valve is not properly biased (negatively) due to the current taken by the grid. A reversed C battery will cause a set to be almost inoperative."
Thus the primary object of Lowenstein was to eliminate distortion. His specifications show that the distortion which he sought to eliminate was that which arises in the circuits as distinguished from that arising in the tube itself. He had ascertained by experiment that relays which function according to current values cannot remedy this distortion. Therefore he sought a way to make his relay function without permitting the flow of any current; i.e., according to terminal voltages as distinguished from current values. The court below stated: "The controversy as to the scope and meaning of this patent arises out of the construction to be given to the following paragraph of the specification: "The potentials created in secondary 13 are made to control the current flowing through the ionic field and originating in battery 21 by connecting the one terminal of coil 13 to the modulating member 18 and the other terminal of said coil to a point on the battery 21, which is located ultranegatively relative to the negative point of the battery connected to the filament." The plaintiffs' position is that these words must be interpreted as meaning that the grid was connected to a point on the battery 21, more negative than any part of the filament. The defendant's position is that a grid biasing potential, more negative than the most negative potential point of the filament, is not disclosed."
This controversy arises because the diagram of Lowenstein does not show which way the filament of the A battery is connected, and therefore it cannot be determined which is the negative end of the filament. If the battery 21 is connected to the negative side of battery 19, then the grid would necesssarily be negative to all parts of the filament. If the battery 21 is connected to the positive side of battery 19 then the grid would be negative with respect to all parts of the filament only if the C battery had a higher voltage than the A battery. The diagram does not help in determining these things. In the specification as original filed, Lowenstein stated that the terminal of the transformer 13 was connected to a point on the battery 21, preferably located ultranegatively relative to the negative point of the battery connected to the filament. The meaning which Lowenstein intended to give to the term "Ultranegative" appears in the prosecution of the case in a response under date of August 6, 1914, by Lowenstein to an action by the Patent Office, citing Von Lieben as an anticipation. Lownstein said: "Von Lieben grid H is positive as against the negative portion of the filament; therefore, a negative current actually flows from that portion of the filament to the grid H. Therefore this is not a disclosure of a potential operated device. As to claim 4, it seems only necessary to point out that the disclosure cited does not permit of making the grid H ultranegative, that is, more negative than any part of the filament; while claim 4 expressly sets forth this feature."
The Examiner finally acquiesced in this view. Thus it is established that Lowenstein intended his grid to be negative with respect to all parts of the filament.
The pertinent prior art referred to below, and to which we should refer, is the Von Lieben tube in which the grid potential is adjustable by a resistance connected across the filament terminals. With this arrangement, the grid potential can be varied, but it can never be made more negative than the negative end of the filament. Current always flows in the control circuit, and Gherardi and Jewett (Defendant's Exhibit, p. 1278) point out that serious distortion results from this. The defendant argues that Von Lieben taught the necessity of an adjustable grid potential, but nothing in Von Lieben suggests that the grid should be negative. There is no such teaching because the Von Lieben tube requires a positive potential on the grid and it would not work at all if the grid were maintained more negative than any part of the filament.
Lowenstein defines the meaning of the term "ultranegative" as being more negative than any part of the filament, and it is unnecessary to consider the question, What bias was suitable for the earlier De Forest tubes? Lowenstein could only have made his invention by observation, and it is clear that the tubes he produced had the effect which he described.
Apparently Von Lieben's is a device of an entirely different character from the audion. It operates by virtue of the very thing that renders the audition wholly inoperative; the potential of its control electrode was positive and could not be made ultranegative; distortion producing current always flows in the control circuit, and cannot be avoided. The positive potential was essential to its ...