In addition to the defense of invalidity the defendant contends that its 23-A and 355 E-1 transmitters do not in any event infringe upon any method suggested in plaintiff's patent. Since evidence and argument are in full in this area of the case an examination of the issue of infringement seems expedient in addition to the finding of invalidity.
Plaintiff contends that the principle involved in the manual operation of the switch as described in his patent is identical when the operation is carried on in a circuit wherein the means of heating filaments of audion and rectifier tubes and, after a proper time interval, applying high plate voltage is automatically effected. He further contends that since the same operation that is performed by the knife switch manually operated method is inherent in a method of operation by automatic means, which is merely a refinement of the method and apparatus of his patent and designed to adapt his invention to the use of circuits energized from an alternating current supply, the alleged infringing devices of the defendant fall into this classification and trespass upon his invention.
In the first of the defendant's allegedly infringing devices, the 23-A transmitter, no batteries are used. Alternating current is supplied through the main power switch which energizes the audio transformer, then the power can be supplied to the circuit through a four-position snap switch. When this switch is turned to the position in which the contacts marked "Fil" and "1" are bridged, the primaries of two transformers are both energized. The current induced in the secondary of one of the transformers heats the filament of a tube and the current induced in the secondary of the other transformer heats the filaments of two plate rectifier tubes. After a pause of thirty seconds the switch is turned to the position in which all three terminals marked "Fil", "1", and "3" are bridged. This continues to heat the filaments of the three vacuum tubes previously mentioned and establishes an additional circuit through another switch (which would be closed) to the winding of a relay.This closes the contacts of that relay which close the circuit to the primary of the plate rectifier transformer. The secondary of this transformer then supplies high alternating voltage to the plates of the rectifier device and current then flows unidirectionally and alternately between the filaments and plates of these tubes.
The defendant insists that although the snap switch is used to supply filament heating current to the amplifier tube and to the plate rectifier tubes and, after delay of thirty seconds, to supply plate current to the amplifier tube, this switch does not respond to the limitations of either claim 1 or claim 2 of plaintiff's patent. It submits that it cannot be found that this switch is actually interposed in a common leg or portion of the plate and filament circuits of the amplifier and plate rectifier tubes and that the switch only indirectly through the filament transformer connects alternating heating current to the filament of these tubes and is not in the plate circuit of any of them. It further submits that the switch merely closes the contacts of the relay, which causes alternating current to be supplied through the separate transformer to the plate circuits of the rectifier tubes which in turn supply direct current to the plate circuit of the amplifier tube. It further submits that the application of heat to the filaments of the tubes in the 23 -- A transmitter, although admittedly thoriated tungsten filament tubes, was not intended for the purpose of reactivating and did not reactivate these tubes. The filaments of the tubes were heated first in accordance with the established practice to prevent injury to the tubes because, as defendant says, if they are not heated first an are may start in the tube due to the sudden shock of the applied voltage and if the tube does not burn out some other part of the circuit may be injured.
In respect of claim 2, the defendant likewise submits that there is no infringement by the 23-A transmitter because it does not have separate energizing means for the plate and filament circuits such as are specified in plaintiff's patent. The four-position switch in the 23-A transmitter, furthermore, does not have one of its contacts connected in a common leg of the plate and filament circuits as in the plaintiff's patent. For these reasons defendant seeks to exonerate its 23-A transmitter from the charge of infringement of plaintiff's patent.
Defendant's 353-E-1 transmitter is also operated without batteries from an alternating current source. It is equipped with a double pole single throw snap switch having on and off positions. By manual operation of this switch the whole transmitter system may be started in the correct sequence. Closing of this switch first applies power to the audio transformer through two switches which would be closed. This immediately lights the filaments of all the amplifier and rectifier tubes by supplying alternating current to them through the transformers employed in the device. At the same time a relay is energized. This is a time delay relay which closes its contacts after approximately one minute. When the contact of this relay is closed the other relay operates to close the circuit for the bias plate rectifier transformer which furnishes plate power for the bias plate rectifier device. When current flows in the plate circuit of the bias plate rectifier, still another relay closes and supplies power to the primary transformer which energizes the plates of the intermediate plate voltage rectifier consisting of the several tubes employed. The closing of the original switch also operates a relay and supplies filament heating current to each of a number of vacuum tubes through transformers. The operation of this relay also supplies current to a relay which after a delay of forty-five seconds puts in operation the grid bias rectifier for the high power stage consisting of two tubes. By a system of closing relays a delay of five minutes is caused before there is put into operation the high voltage power rectifier.
Plaintiff reiterates his contention in the case of this transmitter as in that of the 23-A device that the filaments of the tubes are heated first in order to protect them and the circuits from injury from sudden shocks.Some of the tubes in this transmitter are thoriated tungsten tubes but there are no such tubes in the power amplifier.Again the defendant claims that its device does not infringe claim 1 of the plaintiff's invention (the only claim allegedly infringed by this device), because the switch is not interposed in a common leg of the filament or plate circuit and because its transmitter system is not operated for the purpose of reactivating the filaments of any of the tubes or for the asserted purpose of plaintiff's invention, namely, of preserving "the original condition of the tubes so that reactivation in its strictly technical sense would not be necessary".
Plaintiff fails to disclose in his patent any structural means for automatically delaying the plate potential until the filaments are heated. He makes his initial mistake in assuming that his patent covers the automatic means of delay to which he extends it. I cannot see how his disclosure is infringed by the devices of the defendants which carry out the teachings of the Kishpaugh patents and their knowledge of the art known long before plaintiff's invention in a manner not disclosed in the patent of the plaintiff. I find that the plaintiff has failed to prove infringement upon the part of the defendant.
Findings of fact and conclusions of law will be settled and a decree signed in favor of the defendant.