Institute of Brand and Innovation Law


Myth 4 - Fleming’s Diode patent retarded early US radio development

This post exposes the myth that enforcement of Fleming’s Diode patent retarded early US radio development.

Fleming diode

13 March 2019

The Myth

The myth is that development in early US radio was retarded as the result of the Marconi Co.’s 1916 victory in its suit for infringement against De Forest, inventor of the revolutionary three-electrode vacuum tube.[1] 'The court decided that De Forest had infringed the two-element Fleming vacuum tube, while Marconi had infringed the three-element De Forest patent. Neither company could manufacture the triode' (our emphasis).[2] An early Federal Trade Commission report into radio patents went further, '[T]he court holding that the Fleming patent dominated the use of a vacuum tube either as a detector, repeater, amplifier, or oscillator (our emphasis). As a result of this decision the De Forest Co. ceased manufacturing vacuum tubes in their improved form…' [3] 

It is sometimes argued that this alleged Fleming–De Forest development block was typical of the many independently-held and fundamental patents in early US radio. So, the argument goes, the government was forced to intervene. 'Not until 1919, when RCA [Radio Corporation of America] was formed (at the urging of the Navy) to break the patent logjams besetting the industry, was the impasse finally resolved (Merges 1994, pp. 85-87).' 

The Facts from John Howells and Ron Katznelson

The myth is built on a repeated error of interpretation of the 1916 court decision Marconi. In fact, this court decision found De Forest’s commercial device, his 'audion detector', sold as the name suggests as a radio wave detector, to infringe the Fleming patent construed as a patent on a radio wave detector. The decision specifically excluded from its scope the amplification property of De Forest’s invention and therefore could not block or retard the development of this (or any other) revolutionary physical property of De Forest’s vacuum tube invention.

The narrower question remains whether these court decisions led to the actual blocking of production of De Forest’s triode detector devices. The court decisions did enable the Marconi Co, the owner of the Fleming diode patent, to use injunctions to close down the De Forest’s Company’s production and sale of his infringing detector devices for civil use. Yet the empirical evidence shows that De Forest’s company continued to produce and sell triodes and triode-devices through and after the 1917 affirmation of the district court’s decision. This decision coincided with World War One (WW1) when the military provided the major market for radio equipment and civil radio markets had been suspended. Just prior to the resumption of civil markets in radio equipment in 1919, the Marconi Co. chose to enter into a tripartite cross-licensing agreement with the De Forest and Moorhead Companies which enabled continued production of triode devices under De Forest’s retained rights in his invention to supply amateur radio markets.

A law of 1910 [4] and ensuing case law ensured that during WW1 no supplier of patented goods to the government could be sued for infringement – instead restitution for lost royalties could be sought from the government in the Court of Claims. The result was that immediately post-War many firms were in possession of plant and product designs, which, should they be used to supply forthcoming civil markets, would infringe on many other firms’ patents. In principle, a variety of licensing arrangements could have resolved this situation without the need for litigation. What actually happened was that the US Navy introduced its own, 'nationalist' motivation when it dissuaded General Electric (GE) from licensing patents to the British Marconi Company in favour of some kind of national, US-owned radio company. The Navy then left GE to organise the cross-licensing arrangement as it saw fit. Later, the divisions of market share between the members of the agreement would become the subject of antitrust attention. 

(Find fuller discussion here.)


There was no patent-induced retardation of radio development and no 'log jam' that required US Navy intervention for its resolution. If Fleming’s patent was a pioneer patent it was pioneering in making use of vacuum tube technology in radio and not a patent of broad and controlling scope over the field.


[1] Marconi Wireless Tel. Co of America v. De Forest Radio Tel. and Tel. Co., 236 F. 942, 946 (S.D.N.Y. 1916). Affirmed 243 F 560 (2nd Cir. 1917), hereafter Marconi.
[2] Maclaurin, WR (1971), Invention and Innovation in the Radio Industry, Arno Press: New York, p85.
[3] Report of the Federal Trade Commission on the Radio Industry in Response to House Resolution 548, 67th Congress, 4th Session. Washington DC: GPO, 1924, p26.
[4] Public Law 61-305, Ch. 423, 36 Stat. 851, (June 25, 1910).