WESTERN ELECTRIC CO. v. WALLERSTEIN
60 F.2d 723 (1932)
Circuit Court of Appeals, Second Circuit.
July 18, 1932.
The claim allowed to Gertz provides for "arrangement for amplification of variable electric currents by means of electron relays consisting of a hot cathode, grids and anodes, characterized by the fact that the circuit of the incoming current is connected to the grids and the circuit of the amplified current is connected to the anodes, and by the fact that for the positive charging of the latter a neutral point on the circuit, connected to the anodes is connected to a point on the potentiometer across the current source which is feeding the hot cathode, all for the purpose of eliminating the disturbing effects of a possible alternating current produced in the source, as for instance the commutator ripple in dynamos."
In view of what is thus disclosed in the patent to Gertz, claims 6 and 8 of the Blattner patent are invalid.Colpitts Patent.
Colpitts patent, No. 1,128,292, for an electric wave amplifier, was filed January 3, 1914, and issued February 16, 1915. This patent was held valid and infringed below as to claims 1 and 5. It relates to electric wave repeating apparatus and particularly to the use of vacuum discharge repeaters as exemplified by an audion.
The plaintiffs contend that it covers the push-pull circuit with three-electrode vacuum tubes such as the De Forest audions. The defendant's claim is that this alleged invention devised no new circuit arrangement, but merely connected two De Forest audions in the already well-known push-pull circuit, and it is said that there was no invention involved in substituting audions for old repeaters in this old circuit. The push-pull circuit is one in which two similar performing devices are oppositely connected so that their fundamentally like operation produces an additive result, but, being opposed, the defects of one cure the defects of the other. The basis of this is that the fundamental frequency is amplified and preserved while the even harmonics which tend to produce distortion oppose each other and are thereby reduced. The push-pull circuit is well known (Dean, 1895, patent, No. 549,477). Dean described it in his claim as "the combination with a local transmitter circuit comprising two parallel branches, of two induction coils having their primaries included one in each of the branches of said transmitter circuit and their secondaries included in series in the telephone line, a microphone included in each of the branches of said transmitter circuit, means for increasing the resistance through one of the microphones simultaneously with a decrease of resistance in the other microphone, and a source of electricity connected with
said telephone line adapted to direct current through said branches in parallel; substantially as described."
In the Dean patent, the telephone voice currents to be transmitted arose from the movement of the microphone diaphragm by direct impact thereon of sound waves in air, set up by the voice of the speaker. The push-pull circuit was later applied with different forms of telephone repeaters and amplifiers. When the telephone repeater or amplifier is used, the sound waves do not impinge directly on the diaphragm, and the diaphragm (a carbon button repeater) is moved by the push and pull of the electromagnets connected to the input circuit of the repeater. The carbon microphone amplifier repeater was known in another form prior to Colpitts (Kitsee, No. 770,296, 1903; Grissinger, No. 1,198,212, 1916). Defendant's amplifier has a push-pull circuit as an amplifying repeater. The repeater elements are not actuated directly by the voice, but are actuated electromagnetically by the energy coming to the repeaters from the input circuit. It is clearly established that the mode of operation of these push-pull circuits is the same, and it is as described in the claim of the Dean patent. It is also clear that the defendant used the push-pull circuit of the Dean patent with the De Forest audion. There was a well-known advantage of using the push-pull circuit with an amplifier. The defendant maintains that it was not invention to use the De Forest audion in this old telephone circuit. The De Forest audion was known in 1912. At that time the telephone engineers were seeking an improved telephone repeater to be used in the then known telephone circuits including the old push-pull circuit in place of the older forms of repeaters such as the carbon button which was known as the Shreeve repeater. It was admitted by the plaintiffs' expert Waterman that "the mere placing of devices in a parallel feed arrangement of this sort [Dean, Kitsee, Stragiotti and Grissinger] was, of course, very, very old. It is, in effect, only supplying two devices from a common battery, and it was common to do that in these back-to-back arrangements and in carbon buttons for the purpose of getting added sensitivity." He could not say whether the use of a push-pull circuit with carbon button repeaters and ionic repeaters was familiar to telephone engineers of 1912, but admitted that after Dean the telephone man was presumably advised of the use of these double opposed devices. It required no greater engineering skill and no greater inventive thought to make the substitution of the audion in the old push-pull telephone circuit than was required to make the same substitution in the old two-way long-distance telephone repeater circuits. The use of De Forest audions by Colpitts in the old push-pull amplifier circuit was another obvious engineering use. It was something which had been furnished to telephone engineers by De Forest in October, 1912. With such simplicity to engineers, expert testimony cannot help to bring it to the height of invention. General Electric Co. v. Steinberger, 214 F. 781 (C. C. A. 2). With this knowledge extending over a long period of years, matters of specific structural difference and consequent relative difference of operation between the audion telephone repeater and other types of prior art telephone repeaters that have been used in the push-pull circuits are not of importance. Hewitt v. Amer. Tel. & Tel. Co., 272 F. 392 (C. C. A. 2); Marconi Wireless Tel. Co. v. De Forest Radio Tel. & Tel. Co., 243 F. 560 (C. C. A. 2).
It was well known in 1912 how to apply the energy that is to be amplified to the control element (grid) of an audion. The De Forest audion amplifier (patent No. 841,384, 1907) showed the way to apply energy to be amplified to the three-electrode audion and also the relation of that type of connection to the connection that is used when energy to be amplified is applied to an ionic relay controlled by a magnet. It did not require inventive thought for an engineer to know that in connecting two audions in parallel circuits you must apply the input energy to the grid filament circuits of both of them, and that, if the parallel circuits are to act in push-pull relation, you must reversely connect the input circuit to the two audion grid filament circuits. This is all that is meant by the divided input circuit referred to in claim 1 of the Colpitts patent. He put at the end of the input circuit two input transformer coils just as the carbon button repeaters and the ionic repeaters had put at the end of the input circuit two magnet coils. The secondary coils of the two input transformers were then connected reversely, one to each of the two audion grid filament circuits. In this way the straight audion hook-up was substituted for each branch of the prior art push-pull circuit, which was of common knowledge.