Westinghouse Electric & Mfg. Co. v. De Forest Radio T. & T. Co.

• Decision Date: 06 October 1927
• Docket Number: No. 3563,3624-3627.,3563
• Citation: 21 F.2d 918
• Parties: WESTINGHOUSE ELECTRIC & MFG. CO. v. DE FOREST RADIO TELEPHONE & TELEGRAPH CO. and four other cases.
• Court: U.S. Court of Appeals — Third Circuit

21 F.2d 918 (1927)

WESTINGHOUSE ELECTRIC & MFG. CO. v. DE FOREST RADIO TELEPHONE & TELEGRAPH CO. and four other cases.

Nos. 3563, 3624-3627.

Circuit Court of Appeals, Third Circuit.

October 6, 1927.

Drury W. Cooper, Thomas Ewing, H. Frank Wiegand, and Howson & Howson, all of New York City, for appellant Westinghouse Electric & Mfg. Co.

Harry E. Dunham, of Schenectady, N. Y., Ralph B. Evans, of Philadelphia, Pa., and William G. Mahaffy, of Wilmington, Del., for appellant General Electric Co. and another.

Harry E. Knight, Clifton V. Edwards, and Octavius Knight, Sp. Asst. Attys. Gen., for the United States and another.

Samuel E. Darby, Jr., of New York City, Thomas G. Haight, of Jersey City, N. J., and F. B. Bracken and Morgan, Lewis & Bockius, all of Philadelphia, Pa., for appellee De Forest Radio Telephone & Telegraph Co.

William R. Ballard, of New York City, and Ward & Gray, of Wilmington, Del., for appellee American Telephone & Telegraph Co.

Carroll R. Williams, of Philadelphia, Pa., for Federal Telephone Co., amicus curiæ.

Walter H. Pumphrey, of New York City, for A. H. Grebe & Co., amicus curiæ.

Before BUFFINGTON, WOOLLEY, and DAVIS, Circuit Judges.

WOOLLEY, Circuit Judge.

These cases concern the priority of conception and reduction to practice of a great invention in radio or wireless signalling systems. Though the main issues are purely of fact they are far from simple. This is because of the highly technical character of the still mysterious art out of which they arose and, also, because of the difficulty the lay mind has in comprehending the invention and discovering its place in a train of scientific facts without a previous knowledge of the relation of those facts one to another and, when brought together in one structure, without a clear notion of how the thing works. Of course we shall not presume to say what radio really is, for no one has told us; and, so far as we can learn from an independent study of text books on the subject, no one knows. Yet the behavior of certain scientific data in the transmission and reception of sounds between widely separated points is known. This opinion will, therefore, be addressed to those who, of their own knowledge of the art in action, can pick up any branch of radio organization at any stage and, without more than an elementary statement of what went just before, can understand the invention in suit and the place it took when it entered the art.

Prior to 1912 it was well known that sounds, as of the voice or a musical instrument, could be transmitted for what then seemed great distances through the medium of electro-magnetic waves created by electrical vibrations. Originating at a sending or broadcasting station, these waves radiate in every direction at a rate of vibration, or at a frequency, measured by the number of wave crests which pass a given point per second, amounting sometimes to several million and traveling with a velocity of 186,000 miles a second. When above 20,000 per second they are arbitrarily said to be of radio frequency and cannot be heard by the human ear. When waves of this type strike the antennæ of a distant receiving set and impose upon them waves of the same high frequency, it is the function of that apparatus to convert them into waves of lower frequency, or below 20,000 per second, so that they may be audible. When thus converted they are appropriately termed waves of audio frequency. Waves of radio frequency are sent out by an alternating current, but before they will transmit sound their frequency must not only be reduced or converted to the audible state but the current must be transformed from an alternating current to a pulsating direct current through which alone sound is carried to the ear.

While the invention in suit relates to apparatus for both the transmission and reception of sound waves, it is used mainly in apparatus for their reception. We shall, for convenience, speak of it only in that aspect.

A receiving set in the early days of this still young art was, and still is, a complicated arrangement of electrical parts, the essentials of which (for our purpose) include (1) an aerial, (2) a lead-in wire, (3) a detector, (4) head telephones or receivers, and (5) a ground connection. Further limiting our description of the apparatus to which the invention more directly relates, it will be enough to say that of these several elements we are mainly concerned with the detector. The function of that device — which might more appropriately be termed a rectifier — is to rectify, convert, or filter radio frequency vibrations coming through the receiving aerial into vibrations of audio frequency. The detector in general use in 1912 and 1913 was the vacuum valve, thermionic valve or vacuum tube. It was first conceived by Fleming, an English inventor, and improved by De Forest, a claimed inventor of the invention in suit, and named by him the audion. For many years it had been known that a metal filament heated in a vacuum will give off millions of minute particles or negative charges of electricity, called electrons, in much the same fashion as a piece of iron raised to white heat in a blacksmith's forge throws off sparks. Fleming took a vacuum tube with a heated filament and placed near it, but apart from it, a cold metallic plate within the zone of the myriads of electrons emitted by the filament. He called this a glow lamp, or oscillation valve, and discovered that, by a sort of valve action, it would pass electricity better in one direction than in the opposite direction, or, in other words, the valve had the property of rectifying alternating current similar to but very much better than that of the crystal which had previously been used as a detector. By placing the valves in series with a source of radio-frequency oscillations, he found that one-half of each oscillation could be suppressed, and the circuit would then be transversed by a pulsating direct current, and the desired sounds be transmitted through the receivers.

De Forest improved on Fleming's invention by adding a third element in the form of a metallic cage or spiral of wire which he called the grid. He discovered that at the same time electrons pass from the filament to the plate some of them could be intercepted by the grid and stored up on it. Electrons thus collected and stored (constituting a negative charge of electricity) are released by a positive charge which, when reversed, restores its negative action and thus assists in rectifying the alternating current. With this preliminary and very elementary statement of what Fleming and De Forest did, it is enough for our purpose to note that the audion, though resembling an incandescent lamp and, like the lamp, being highly exhausted of air or gas, differs from it in its vacuum contents in that it comprises three electrodes; (1) a metallic filament which is electrically heated to incandescence through external contact points, (2) a cold metal plate placed apart from the filament, having an external contact point (the invention of Fleming), and (3) a cold metallic cage or spiral wire called the grid, intermediate the filament and plate and apart from both, having an outside terminal (the invention of De Forest).

The audion, as conceived by Fleming and perfected by De Forest, together with its appropriate electric currents, is now in universal use and is the basis of the modern art of transmitting sounds great distances both by wire and through the air.

We now come to the invention in suit which deals primarily with circuit arrangements in connection with the detector parts we have just described. The standard audion hook-up in 1912 consisted of three circuits: (1) The filament circuit, connected with the filament's two external contact points and supplied with energy by the A battery; (2) the input or grid circuit, one terminal of which was connected with the hot electrode or filament and the other with the grid; and (3) the output, plate or wing circuit, one terminal of which was connected with the filament and the other with the plate, the latter being actuated by the B battery. The input or grid circuit, being coupled with the antennæ, received the incoming waves of radio frequency which the audion then converted into waves of audio frequency in the plate or output circuit, whence the electrical vibrations were carried by a wire connection to a receiver and finally to the human ear in the form of sounds. With this circuit arrangement in mind, the remaining one of many scientific facts which it will be necessary to state is that, although the valve action of the grid was a great improvement over earlier detectors in rectifying alternating currents, the incoming oscillations, after traveling many miles from a broadcasting station and losing power as they proceeded through the air would die down and when they reached the receiving station would be feeble and, in consequence, the efficiency of the system would become limited in area and audibility. Just here, some time in 1912 or 1913, four men in distant parts of the world, it is claimed, made the same discovery that by coupling up the output plate circuit with the input grid circuit (either by physical connections or induction) the weak incoming radio oscillations could be built up and greatly strengthened — indeed, they could be strengthened several hundred fold — and thus the area of sound transmission be vastly extended and audibility greatly increased. The reason given for this is that by hooking up the output circuit with the input circuit in one of several ways the current of the latter is strengthened by a magnetic flux set up by the former; the operation, wherein the energy of each circuit reacts upon the other, repeats itself a great number of times with cumulative effect until an amplifying alternating current is produced whose frequency can be controlled by varying the electric constants in the assembled circuits. A current of...