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The Vacuum Tube Situation by Elmer Cunningham
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The following article appeared in the February 1920 issue of Pacific Radio News. A reference to this article appears in the book Saga of the Vacuum Tube by Gerald Tyne. Here is the text from this rare magazine. Thanks to Alan Douglas for providing a xerox of the text. Note that the phrases in ALL CAPS are as they appeared in the article, and I am sure they were intended as emphasis.
The Vacuum Tube Situation
By E. T. Cunningham
The attorneys for the Radio Corporation of America (formerly Marconi Company) have been issuing a statement to the effect that Judge Mayer has decided that not only audions, but also amplifiers and oscillions are infringements of the Fleming patent owner by their client. In the opinion of our counsel, Messrs. White and Prost, this statement is most misleading, is not justified by Judge Mayer's opinion, and is in direct conflict with the DISCLAIMER filed in the U.S. Patent Office by the assignee of the patentee, John A. Fleming. We present the following facts that you and your readers my understand the exact situation:
On October 21, 1884, there was issued to Thos. A. Edison, patent No. 307,031, for "electrical indicator," embracing an evacuated bulb containing a hot filament and a cold electrode with a flow of current between the two; in other words, a structure identical with that of Fleming. As said by Judge Mayer in Marconi Co. vs. De Forest Co. 236 Federal Reporter 946:
"Stripped of technical phraseology, what Fleming did was to take the well known hot and cold electrode incandescent lamp of Edison and use it for a DETECTOR of radio signals. No one had disclosed, nor even intimated, the possibility of this USE of a device then LONG KNOWN IN ANOTHER ART."
From the foregoing, you will see that, according to Judge Mayer, Fleming did not invent A NEW DEVICE, but merely suggested a NEW USE of an OLD DEVICE and which USE is that of a DETECTOR of RADIO FREQUENCY alternating currents.
In the above mentioned suit only several patent claims were involved or considered by the court, to-wit; Claims 1 and 37. Claim 1 reads as follows:
"1. The combination of a vacuous vessel; two conductors adjacent to, but not touching each other in the vessel; means for heating one of the conductors, and a circuit outside the vessel connecting the two conductors."
This claim accurately describes and covers the Edison hot ad cold electrode lamp and therefore, if not limited with respect to USE, would be anticipated by such Edison device and therefore VOID.
Appreciating the foregoing situation and in order to save this claim, the assignee of Fleming filed in the U. S. Patent Office a document known in law as a "disclaimer," whereby he disclaimed the idea that his STRUCTURE was new and limited his patent monopoly to one and only one particular and specific use, to-wit: the USE as a rectifier in connection with high frequency alternating electric currents of the order employed in Hertzian wave or wireless transmission. The following is an exact copy of such disclaimer:
DISCLAIMER: 803,684. John Ambrose Fleming, London, England. Instrument for converting alternating electric currents into continuous currents. Patent dated Nov. 7, 1905. Disclaimer filed November 17, 1915 by the assignee, Marconi Wireless Telegraph Company of America. Enters this disclaimer: "To the combination of elements set forth in Claims 1 to 6, inclusive, and 10 to 15, inclusive, respectively, of said Letters Patent, EXCEPT AS THE SAME ARE USED IN CONNECTION WITH HIGH FREQUENCY ALTERNATING ELECTRIC CURRENTS OR ELECTRIC OSCILLATIONS of the order employed in Hertzian wave transmission, and to the words in the specification: 'Whether of low frequency or' at page 2, lines 32 and 33; 'either,' at page 2, line 98; and 'or low frequency alternating currents of,' at pages 2, lines 98 and 99."
Copy of Fleming Patent No. 803,684, dated Nov. 7, 1905, and the above disclaimer may be obtained for 10 cents from the Commissioner of Patents, Washington, D. C.
As said by Judge Mayer, "Claim 1, as limited by the DISCLAIMER, is a broad claim for the incandescent lamp AS A RADIO DETECTOR."
In other words, CONTRARY TO THE STATEMENTS OF MESSRS. SHEFFIELD & BETTS, Judge Mayer held that Claim 1 limited to a DETECTOR and nowhere, in his opinion, is there any suggestion that this claim covers the OLD EDISON DEVICE when used as an AMPLIFIER or OSCILLION. In fact, such USES of this old device are impossible with the two-member Fleming rectifier, and were never dreamt of by Prof. Fleming at the time he applied for his patent, and at such time were not known to anyone else. As Fleming's entire invention consisted of suggesting a new USE of this OLD EDISON DEVICE, to-wit: As a detector operating to rectify radio frequency alternating currents, it must be obvious to you that no court could adjudge this Fleming patent to cover other USES not possible with his structure, not thought of by Fleming and consequently NOT INVENTED by him. Furthermore, an amplifier, as used in audio frequency circuits, comes within the Fleming DISCLAIMER and therefore cannot be covered by his patent.
Claim 37 reads as follows: "37. At a receiving station in a system of wireless telegraphy employing electrical oscillations of high frequency a DETECTOR comprising a vacuous vessel, two conductors adjacent to, but not touching each other in the vessel; means for heating one of the conductors; a circuit outside the vessel connecting the two conductors; means for detecting a continuous current in this circuit, and a means for impressing upon the circuit the received oscillations."
You will note this claim is specifically limited to a DETECTOR and therefore does not cover an amplifier or oscillion.
The previous attitude of the Marconi Company confirms the foregoing, as numerous concerns, according to our information, are using without license from such company, audions as amplifiers and oscillions. The Western Electric Company and the American Bell Telephone and Telegraph Company and affiliated companies are making and using three-member tubes as amplifiers and oscillions in long distance telephony and telegraphy; the DeForest Radio Telephone & Telegraph Co. are making and selling oscillions or audion generators to be supplied with their wireless telephone sets. See advertisement, page 706, of the November Electrical Experimenter and the DeForest trade notices. The General Electric Company make and sell the Tungar rectifier and the Coolidge X-ray tube, both embodying the old Edison structure claimed by Fleming.
We feel quite certain that the AudioTron does not infringe the Fleming patent, no matter to what uses it may be put, and we are prepared to attack the validity of such patent.
However, as the use of our device as an amplifier in audio frequency circuits is clearly within the specific language of the Fleming disclaimer and therefore cannot infringe such patent, we are selling same for that use only, although we have a license from the DeForest Company which permits us to sell it as a detector or amplifier for amateur purposes only.
In the DeForest litigation the Marconi Company contended that the grid and plate elements were merely the Fleming plate divided into two portions and that the two electrodes performed the same function as their one electrode. While the Fleming patent is for a rectifier of high frequency currents only and did not specify the use of a local battery, Judge Mayer held that Fleming had the right to use his device in the ORDINARY detector circuits of the PRIOR ART. At Fleming's date (1905) amplifier and oscillating circuits were unknown, and as is well known to all radio engineers, it is impossible to substitute the two-member Fleming rectifier in the three-member audion amplifier and oscillating circuits and obtain the same results. This proof is sufficient to show that the mode of operation is different and that therefore an amplifier or oscillion cannot be an infringement of the Fleming patent.
I have not attempted to go into detail except in respect to an audio frequency use in radio work of an improved form of the old Edison device and to show that such use is not an infringement on Fleming. In the Marconi-DeForest litigation, DeForest was unable to prove a difference in mode of operation between a two-member and a three-member tube and since such a difference does exist and we believe it can be proven beyond a reasonable doubt, the use of the three-member audion is not an infringement of Fleming.
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