introduction of Variable Mu tube

[PRR]

While the commercial announcement is Cunningham, I think the idea and development goes to Stuart, B & Snow, H. A. (1930).

 

[JonSnell Electronic]

​

Name:	Cunningham Inc., E.T.; Harrison (NJ) (USA)
Abbreviation:	cunningham
Products:	Tube manufacturer
Summary:	E.T. Cunningham, Inc., Harrison, New Jersey. Elmer T. Cunningham registers his trademark AudioTron on March 30, 1916 but sells AudioTron tubes since August 1915 with first advertisements in November 1915. On June 15, 1920, Cunningham gets two agreements with the new RCA where he has to drop his production and gets deliveries granted by RCA for his trade name.
Founded:	1916
Production:	1915 - 1920
History:	Elmer T. Cunningham registers his trademark AudioTron on March 30, 1916 but sells AudioTron tubes since August 1915 with first advertisements in November 1915. The AudioTron (also written as Audio Tron or Audiotron) was made in Oakland, California. In for about three months in 1916/17 Cunningham sold also these double ended tubes with two filaments under the brand Amplitron. By April 6, 1917, the dismantling and sealing of amateur equipment because of the war brought an end to this production witch again started in June 1919 (Advertisement), now using a thoriated-tungsten filament with a life of 2000 hours. In June 1920 Cunningham gets a license for his AudioTron Manufacturing Company, former called AudioTron Sales Company to sell tubes in his name made by RCA. In turn he has to stop his own patents infringing production. In December 1922 the name Audiotron drops from his adds and the business is named E.T. Cunningham Inc. In April 1931 it is "A Subsidary of Radio Corporation of America". Details see Tyne "Saga of the vacuum tube" page 160ff. Harry V. Roome in Los Angeles, a 17 year old high school boy sold a very similar tube from January 1916 to August 1916 called Oscilaudion. In July 1916 he named the tube also ThermoTron (The Thermo Tron Company).

 

[sser2]

The relationship between RCA and Cunningham is a mystery. The natural course for RCA would have been to seek "seize and desist" order for Cunningham to stop it from infringing on RCA patents. But for some unknown reason RCA chose appeasement: they entered into contract to supply Cunningham with their tubes to be sold under the Cunningham brand. Cunningham must have had some secret power over RCA.

Type 35 is the first example of a remote cutoff pentode.

 

[jhstewart9]

Here the 35 appears in the RCA Cunningham RC11 Tube Manual, published in 1933.

 

[jhstewart9]

Details see Tyne "Saga of the vacuum tube" page 160ff.
-----------------------------------
Saga of the Vacuum Tube pdf

.https://nvhrbiblio.nl/biblio/boek/Tyne%20-%20Saga%20of%20the%20vacuum%20tube.pdf

A very good reference, I bought a copy soon after it was published in 1977.
And original copies for sale on the iNet at crazy asking prices. Check it out!😱

 

[PRR]

I did not mean to re-open the Cunningham debate.

There is no big mystery. RCA was a patent-license office with Davey the telegraph-boy dreaming big. Elmer was a production wizard. Also skilled at keeping production workers compliant and docile. At getting police and newspapers on RCA's side when the workers walked-out and needed beatings. His influence could still be felt at Camden, and in the memories of old workers, in the early 1960s (though he had not been in town in years). See also Ford and Sorensen.

The "variable Mu" tube has a still-ongoing place in the history of audio, as gain-control in limiters; which greatly improved both disks and film.

 

[PRR]

Here's a notable picture:

Cunningham, Marconi, Sarnoff, in 1934

 

[zintolo]

The relationship between RCA and Cunningham is a mystery.

Maybe you already know this, but it is indeed interesting: https://vacuumtubesinc.com/cunninghampage

The first agreement gave Cunningham a license to manufacture 5000 tubes over a period of 90 days. The second agreement provided that, when the 90-day license had expired, Cunningham's company would cease to make vacuum tubes. "RCA agreed to supply Cunningham with tubes until the expiration date of the deForest patent No. 879,532 on February 18, 1925. The tubes were to be of Cunningham's choice, selected from samples submitted by RCA, and supplied in cartons ready for delivery. Both the tubes and cartons were to bear names and marks designated by Cunningham. There was to be no indication of the name of the manufacturer or RCA. These tubes were to be sold to Cunningham at a discount of 20% below the lowest net price quoted to any other customer." At the very least RCA got an instant West Coast distribution network out of the deal.