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Technidyne Corp. v. McPhilben-Keator Inc.

July 23, 1934

TECHNIDYNE CORPORATION ET AL.
v.
MCPHILBEN-KEATOR, INC.



Appeal from the District Court of the United States for the Eastern District of New York.

Author: Manton

Before MANTON, L. HAND, and AUGUSTUS N. HAND, Circuit Judges.

MANTON, Circuit Judge.

This appeal involves the validity and infringement of seven patents, including a reissue, to Jones and assigned to the plaintiff Technidyne Corporation, known as reissue patent No. 17,915 originally filed August 21, 1925, and issued December 30, 1930; patent No. 1,620,661, application filed March 6, 1926, issued March 15, 1927; patent No. 1,770,525, filed July 15, 1927, issued July 15, 1930; patent No. 1,788,197, filed October 5, 1929, and issued January 6, 1931; patent No. 1,673,287, filed June 11, 1927, and issued June 12, 1928; patent No. 1,779,881, filed October 5, 1929, and issued October 28, 1930; patent No. 1,791,030, filed October 5, 1929, and issued October 28, 1930; and one issued to Bonine, known as patent No. 1,696,263, filed August 12, 1922, and issued December 25, 1928. The eight patents relate to radio tubes and circuits.

Many patents have been issued in this well-developed field, and, as indicated by the date of their issuance, all are of recent grants. Since the radio art was well developed, the standard of inventive thought to sustain a patented radio tube or circuit necessarily is higher than in the earlier history of the art. Kintner v. Atlantic Communication Co., 230 F. 829 (D.C.), affirmed 240 F. 716 (C.C.A. 2); Dubilier Condenser Co. v. Aerovox Wireless Corp., 37 F.2d 657, 660 (C.C.A. 2); Radio Corp. v. Dubilier Corp., 59 F.2d 305 (C.C.A. 3); Western Electric Co. v. Wallerstein, 60 F.2d 723 (C.C.A. 2).

For an understanding of the patents in suit, a brief description of radio operation may be helpful. Radio signals are transmitted and received in the following manner: Speech or music produces sound waves, which have frequencies of alternation or pitch, ranging from about 50 cycles per second to 20,000 cycles. These are called audio frequencies and higher frequencies are termed radio frequencies. At audio frequency sound waves are applied to the diaphragm of a microphone, it vibrates in accordance with the sound waves, causing an electric current to alternate at the same frequency. Audio frequency currents are then applied to the radio frequency current, such as 1,000,000 cycles per second, modulating it. A voice (audio) frequency of 5,000 cycles would vary the radio frequency from 1,005,000 cycles to 995,000 cycles. The audio modulated radio frequency currents are then applied to a transmitting antenna which produces ether waves, corresponding in frequency to modulated currents. A receiving antenna intercepts the waves, thereby setting up radio frequency currents with the same frequency as that of the waves. The radio frequency currents are amplified in the receiver and are then subjected to the process of detection, whereby the audio frequency modulations are separated and appear as audio frequency currents; the radio frequency currents being eliminated. The audio frequency currents are then amplified, and actuate the diaphragm of a loud speaker or telephone receiver, thus producing the sound waves, which have the same frequency or pitch as the original sound waves.

The broadcasting band is from 550 KC to 1,500 KC. A radio wave of electrical current to-day is usually referred to in the terms of frequency; formerly they were referred to in terms of length. Frequency is readily convertible into wave length; either frequency or length can be obtained by a known method of calculation. In a receiver, the radio frequency currents in the antenna are amplified by one or more tube stages. The detector produces audio frequency currents, which are amplified by one or more tube stages and then actuate a loud speaker. A battery supplies energy to heat the filament, which then emits electrons that go to the plate. Another battery supplies energy to the plate circuit and another battery maintains a negative charge on the grid. Lowenstein patent; Western Electric Co. v. Wallerstein, 60 F.2d 723 (C.C.A. 2).

Tuning, or selectivity, becomes necessary because the antenna has as many currents of different frequency as it has intercepted radio waves of different frequencies. The user wishes to receive only currents of one frequency at a given time, and therefore tunes to that frequency so that it discriminates against all other frequencies. In modern broadcast receivers, tuning to stations of different frequencies is accomplished by varying the capacity (condenser).

In the second tube stage of the receiver, there may be no variable tuning and therefore at times it is referred to as an untuned stage. However, it is tuned broadly to a band of frequencies, although not narrowly to a single frequency. The same natural capacities are in the tuned circuit of the first tube, but their effect is very small compared to the large and controlling effect of the variable condenser. But such nonvariable tuning circuits are sometimes referred to as untuned.

The court below treated the patents in groups. The appeal has been argued with the same regard for these groups. The first group (Jones, reissue No. 17,915; No. 1,620,661; No. 1,770,525; No. 1,788,197) deals with tuned circuits, radio tubes, feedback or regeneration, and means for neutralizing or controlling feedback. A tuned circuit is a circuit tuned to a current of certain frequency of alternation. The circuit is tuned to the desired frequency or band of frequencies by adjusting its values of inductance, capacity, or both. Every electrical circuit has each of the three fundamental characteristics of inductance, capacity, and resistance, although the values of each differ greatly in different circuits.

A radio tube comprises a hot cathode which emits electrons that go to a cold anode (plate) both inclosed in an evacuated glass envelope. A grid, also inclosed, is located between the filament and the plate so that, when the varying potential of a signal is impressed upon the grid, the electron stream is correspondingly modified. The electron stream is a part of a powerful electrical current which is modified to produce great amplification of the feeble grid potentials. Regeneration or feedback can be produced in the radio tube when used as an amplifier, because it then has currents in its plate (output) circuit which are greater than in its grid (input) circuit. If the output is coupled to the input, a part of the amplifying energy can be fed back to be added to the in-coming signal currents, and, as modified, will be amplified further by the tube circuits, feedback again occurring, and this will continue on until the losses of the circuits put an end thereto. We have considered controlling a feed back heretofore. Armstrong v. DeForest Radio Telephone & Telegraph Co., 280 F. 584 (C.C.A. 2); Radio Corp. v. Radio Engineering Laboratories, 66 F.2d 768 (C.C.A. 2).

In 1917, Rice improved neutralization by an auxiliary circuit through which energy was fed back to oppose or neutralize the positive feedback. Radio Corp. v. Twentieth Century Corp., 19 F.2d 290 (C.C.A. 2). In 1919, Hazeltine further improved neutralization. Hazeltine Corp. v. Wildermuth, 34 F.2d 635 (C.C.A. 2). Thus the art relating to tuned and untuned radio tubes, feedbacks, and the control of feedbacks was well known prior to the grant of the patents in suit. Men skilled in the art after knowledge of the results of these inventions were fully capable of controlling feedback in amplifiers, and the basic question on this appeal is whether what the inventors did in the patents in suit rose to the dignity of inventive thought or constituted engineering efforts of a man skilled in the art.

Reissue No. 17,915. The first patent of the group (Reissue No. 17,915) is to provide control of feedback in the same untuned circuits. The patent was the earliest of the group as well as the broadest, and has admittedly for its object an improvement of the old radio frequency system (Alexanderson and Rice), so that it will have "an amplification power substantially greater than that attainable in radio frequency systems known to the prior art." And Jones says that by this patent he wanted to use an untuned radio frequency receiver which did not have as much feedback as the usual receiver of that type, so he employed two expedients to reduce the feedback. The first expedient was to not tune the plate circuit of one of the tube stages, and the other expedient was the resistance. Below, this patent was held valid and infringed as to claims 1, 3, 5, 7, 10, 13, 14, 15, and 25.

By untuning the plate circuit (output) that is, by not tuning it to a frequency within the range, the feedback is reduced. This was old in the art before Armstrong tuned the plate circuit to obtain feedback, and the fact that feedback depended upon tuning the plate circuit was fully understood back in ...


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