Hazeltine Research, Inc. v. Zenith Radio Corp. (239 F. Supp. 51, 1965)

AUSTIN, District Judge.

FINDINGS OF FACT AND CONCLUSIONS OF LAW

PART I — ‘FINDINGS OF FACT

I. The Parties, The Action, And The Issues.

1. Plaintiff Hazeltine Research, Inc., an Illinois corporation, is a patent holding and licensing company. Defendant Zenith Radio Corporation, a Delaware corporation, is a manufacturer of radio and television receivers. Both parties have regular and established places of business in Chicago, Illinois, in this District and Division.

2. The complaint alleges a cause of action for patent infringement, and the jurisdiction of this Court arises from the patent laws of the United States. The venue is properly laid in this District and Division.

3. The patent in suit is United States Letters Patent No. 2,547,648, entitled “Automatic Contrast Control System For Television Apparatus”, issued to plaintiff on April 3, 1951, as the assignee of Arthur V. Loughren. Plaintiff has owned the Loughren patent at all times since its issuance. It was granted on an application, Serial No. 120,404, filed in the United States Patent Office on October 8, 1949. That application is asserted by plaintiff to be a “continuation” of a prior application, Serial No. 643,287, filed on January 25, 1946. On the basis of that assertion, plaintiff contends that the 1949 application is legally entitled to the 1946 filing date of the earlier one. Defendant challenges this position, asserting that the 1949 application was not truly a “continuation” and hence not legally entitled to the 1946 date.

4. Defendant is charged with having infringed claims 1, 2, and 4 of the patent in suit, the accused products being television receivers made and sold by defendant. All three of those claims were first submitted to the Patent Office in the aforementioned 1949 application, Serial No. 120,404. None of the claims carried forward from plaintiff’s 1946 application is involved in the case.

5. Defendant denies having infringed plaintiff’s patent, and it further avers that, in any event, plaintiff’s claims in suit are invalid. The invalidity defense rests on these two independent grounds:

(a) Defendant asserts that the patent in suit, insofar as the claims alleged to be infringed are concerned, has an effective filing date of October 8, 1949, when the second application was filed, and that the claims in suit are accordingly invalid by reason of publication of their subject matter, and public use and sale thereof in this country, more than one year before the filing date of the patent.

(b) Defendant asserts that the claims in suit are void, regardless of their effective filing date, for failure to describe any invention patentable over the prior art.

Defendant also pleaded that the patent in suit is unenforceable by reason of its misuse by plaintiff. This defense, however, was reserved for separate trial, along with defendant’s counterclaim seeking damages from plaintiff for antitrust law violations.

II. Facts Concerning Electrical Concepts And Circuit Elements Involved In The Case.

6. The term “current”, in the electrical sense, refers to movement of electric charges. There are two types of electrical charge — positive and negative —but normally only negative charges (known as electrons) are mobile, and in consequence electric current nearly always consists of a flow of electrons. It is a characteristic of electric currents that they can flow only in a closed path or loop, and such a closed path is known in electrical parlance as a “circuit”. A simple circuit may consist of only a single loop; more complex' circuits may involve several interconnected loops.

7. There are two basic types of electric current, known respectively as “direct current” and “alternating current”. A direct current is one that flows around a circuit in only one direction, whereas an alternating current is one which periodically reverses its direction of flow. In television circuits, the currents are often of complex character, involving both direct-current components and alternating-current components.

8. The force that makes current flow in a circuit is commonly called “voltage” or “potential”; it may be thought of as electrical “pressure”, analogous in some respects to hydraulic pressure. Voltage results from the fact that unlike electric charges exert an attractive force on one another, while like charges exert on one another a corresponding repelling force. Anything that will cause a non-uniform distribution of electric charge in an object will create a voltage, and such voltage will produce an electric current if an electrical conductor is provided to complete a circuit between the oppositely charged portions of the object. The common chemical battery is one familiar type of voltage-generating device.

5. Voltage is commonly measured from one point in a circuit with respect to some reference point in the same circuit. In television equipment, the reference point most commonly used is the metal chassis on which the parts are mounted, and this is usually called “ground”, even though in practice there may be no actual conductor joining the metal chassis to the earth.

10. A “resistor” is an electric circuit element intentionally designed to offer resistance to the flow of electric current through it, the amount of such resistance being measured in terms of a unit called the “ohm”. When current flows through a resistor, a voltage proportional in magnitude to that of the current appears across the resistor’s terminals. Accordingly, in addition to being used for other purposes, resistors are often employed in television apparatus to derive from a varying signal current a proportionally varying signal voltage. When thus used, a resistor may be called an “impedance” or “load impedance”.

11. A “capacitor” is an electric device having the property of storing electric charge, analogous in some ways to an elevated water tank. When connected in a circuit with a direct-voltage source, a capacitor will accumulate charge from the source until the stored charge produces a counter-voltage equal to the source voltage. If a charged capacitor is connected into a conductive circuit, it will act temporarily as a voltage source and drive current around the circuit. Because a capacitor, unlike a battery, has no internal means of renewing its charge, however, the voltage of the capacitor will diminish as the current flows and ultimately drop to zero, unless its charge is replenished from some outside source.

12. Of outstanding prominence among the electrical components dealt with in this record are the devices known as “vacuum tubes”. Two types are relevant here — the two-element vacuum tube, known as a “diode”, and the vacuum tube having three or more elements, generically known as a “grid-controlled tube”.

13. A two-element vacuum tube or “diode” consists of an evacuated envelope, usually made of glass, containing one conductive element called a “cathode” and another called an “anode” or “plate”. These electrodes are spaced a short distance apart, with a vacuum in between. The cathode is coated with a material having the property, when heated, of giving off electrons (i. e., negative electric charges) in great quantities. When the anode is at a negative voltage with respect to the cathode, these electrons do not go anywhere; they simply form a “cloud” around the cathode. If a voltage source be connected in a circuit with the cathode and anode so as to charge the anode to a positive voltage with respect to the cathode, however, the attractive force exerted by the positive anode will draw the electrons from the cathode across the intervening vacuum and thus create an electric current in the circuit. No electrons will flow through the diode in the other direction, however, even if the polarity of the voltage source be reversed. Devices, such as diode tubes, which have this property of conducting current in only one direction are known in the electrical art as “rectifiers”.

14. A “grid-controlled tube” is a device which, like the diode, has a cathode and an anode enclosed in an evacuated envelope. It has in addition, however, a third electrode called a “grid”, situated in the space between the cathode and the anode. This grid is formed of spaced wires which do not, in the mechanical sense, prevent the flow of electron current from the cathode to the anode, but which may, by electric forces, control— i. e., regulate — the rate at which such current flows. If the grid be at the same voltage as the cathode, electron current will flow from the cathode to the anode whenever the anode voltage is positive with respect to the cathode, just as in a diode. If the grid voltage be made negative relative to the cathode, however, the rate of electron flow from cathode to anode will be reduced, and if the grid voltage be made sufficiently negative with respect to the cathode, the electron current between cathode and anode will be cut off entirely. Thus the grid performs a function analogous to that of an adjustable valve in a water hose. Tubes having only one grid are called “triodes”, indicating that the tube contains three electrodes. Some tubes have more than one grid and are called “tetrodes”, “pen-todes”, etc., depending on the number of electrodes they contain.

15. All the electrical concepts and circuit elements described in the findings just foregoing were old and well known prior to any of the work on which plaintiff’s patent in suit is based.

III. How Television Pictures Are Transmitted And Received.

16. In a television system, an image of the scene to be televised is projected by a lens system onto the screen of a “camera tube”, where the image is “scanned” by a rapidly moving electron beam sweeping across the image from side to side, each sweep being vertically shifted by a small amount from the path of its predecessor, so that the entire image area is progressively traversed. As this electron beam in the camera tube “scans” the image of the scene being televised, its intensity varies in proportion to the brightness of the various parts of the image; in this way, a varying electric current is generated which represents the degree of brightness of the parts of the image progressively scanned. This current (known as “video signal current”) is employed at the television broadcasting station to generate radio waves having correspondng intensity variations, and these in turn may be picked up by television receivers within the range of the broadcasting station. The receiver circuits utilize the radio waves to develop a video signal voltage that has intensity variations corresponding in pattern to those of the video signal current generated by the camera tube at the broadcasting station. After being amplified by a circuit in the receiver known as a “video amplifier”, this video signal voltage is applied to the receiver picture tube and there used to control the intensity of an electron beam which sweeps systematically across the picture-tube screen, producing thereon a reproduction of the original image televised by the broadcasting station.

17. For the image on the receiver picture tube to correspond to that .transmitted by the broadcasting station, the electron beam in the picture tube must “scan” the receiver screen in exact time synchronism with the electron beam in the camera tube. This is accomplished by modulating the radio waves from the broadcasting station with control signals (known as “synchronizing pulses” or, more commonly, “sync pulses”) which are used in the receiver to govern the timing of the picture-tube scanning. These sync pulses are of uniform magnitude and occur periodically in the video signal voltage, interspersed in time between the portions representing light and dark areas of the picture. Immediately following each sync pulse is another short-duration voltage pulse that represents the so-called “black level”- — i. e., the amount of signal voltage corresponding to a black area of the picture.

18. The television system used in the United States is of a type known as “negative modulation”, in which increasing radio-wave intensity represents darkening, as opposed to brightening, of the transmitted picture. In England, at least until recently, a so-called “positive modulation” system was used, in which increasing wave intensity represented an increase in picture brightness — i. e., the converse of the negative-modulation system. Both these types of television systems were known, and their characteristics understood, long before the work underlying plaintiff’s patent in suit was done. (R. 93, 95-96,103)

IV. Automatic Gain-Control Circuits— Their Purpose, History, and Basic Operating Principles.

19. To do its work well, the picture tube of a television receiver should be supplied with a video signal voltage of reasonably uniform intensity — that is, the range of video signal voltage defining the spread from white to black should be essentially the same whether the receiver is tuned to a powerful station or a weaker one, and notwithstanding changes in atmospheric conditions affecting the strength of the received radio waves. In television receivers, this is achieved by means of circuits known, interchangeably, as “automatic gain control” or “automatic contrast control” circuits. These names are frequently shortened to “AGC” and “ACC”, respectively. AGC circuits for television receivers have been known since a date long prior to the work which led to the patent in suit. All such circuits — prior-art and contemporary alike — operate on the same basic principle, which involves generating an electrical control voltage proportional to the strength of the received radio waves, such control voltage being then applied to the television receiver circuits in such a way as automatically to reduce the amplification when the received signal grows in strength and increase it when the received signal weakens. Hence a video signal voltage of substantially uniform intensity is obtained for operation of the picture tube, despite wide variations in the strength of the radio waves that bring the television signal to the receiver. (R. 74, 153, 275)

20. Even before television, AGC circuits were known and used in connection with sound radio receivers. These two branches of the radio art — sound radio and television — are so related historically and professionally that a skilled worker designing an AGC circuit for television could reasonably be expected to consult the literature ón sound-receiver AGC circuits as a source of ideas. Plaintiff’s expert witness conceded this. (R. 1446)

21. Numerous television AGC circuits —some of them simple and some of them rather complex — had been developed before the work underlying the patent in suit was done. While these circuits varied greatly in their details, they all had in common the development of the AGC control voltage in a so-called “integrating load circuit”, consisting of a capacitor and a resistor connected in parallel. This old feature has been carried forward into modern AGC circuits and is utilized in all the circuits directly involved in this case. (R. 594-595)

22. In one AGC circuit acknowledged to be prior art, the integrating load circuit was supplied with current fed through a diode rectifier from the so-called “video detector” of the television receiver. This developed across the integrating load circuit a d-c voltage substantially equal to the peak magnitude of the, video signal voltage, which, in the negative-modulation television system, was that of the sync pulses. While this AGC system was simple and would work, its control of receiver gain was not as sensitive as might be desired. This deficiency could be overcome by adding a d-c amplifier to raise the magnitude of the AGC voltage before using it to control the receiver gain, but this had the disadvantage of requiring an extra stage of amplifica-ton in the AGC system. (R. 689, 702-704)

23. The simple AGC circuit just described could not be used with “positive modulation” television signals, because in such signals the peak magnitude-would vary with the picture brightness as well as with changes in signal strength. The “black level” portions of positive-modulation television signals were a suitable index of actual signal strength, however, and early television designers accordingly developed AGC systems that were specifically engineered to develop an AGC control voltage proportional to the “black level”. This was done by measuring the signal voltage only at those instants of time during which the black-level component was being received, and the circuits which accomplished that result were known, in the engineer’s jargon, as “reacher-inners”. These circuits, while designed primarily for positive-modulation television, would also work — and equally well — in receiving negative-modulation television pictures. Such circuits were known as early as the 1930’s. (R. 221-222)

V. The AGC Circuit Of The Patent In Suit — How It Was Developed And How It Works.

24. The work underlying the patent in suit was undertaken in the fall of 1945, when Arthur V. Loughren, named in the patent in suit as inventor, was in charge of an engineering group in plaintiff’s laboratory. Loughren’s task at hand was designing a television receiver, and one of the goals desired was an improved AGC system. An engineer named Bailey, in Loughren’s group, suggested to Loughren that a more sensitive AGC -could be secured if one were to start with the video signal voltage derived from the load impedance of the video amplifier, rather than from the video detector. (This was not a new idea, although loughren at that time may have thought it was.) Starting with that lead, Lough-xen developed- the AGC circuit of which several variants were illustrated and described in his original patent application.