MARCHI

Cunningham's story begins with Elmer T. Cunningham and the AudioTron. The tube was on sale by August 1915, appeared in advertisements from November, and its trademark was registered on 30 March 1916. Early AudioTrons were made in Oakland, California. For a short period in 1916–17 Cunningham also offered the Amplitron, a double-ended tube with two filaments. Wartime restrictions on amateur radio equipment stopped this first production in April 1917. An advertisement records its resumption in June 1919, now with a thoriated-tungsten filament advertised as lasting 2,000 hours.

On 15 June 1920 Cunningham reached agreements with the newly formed RCA: he stopped making his own tubes and received RCA-made valves to sell under his name. From then on a Cunningham marking did not necessarily mean independent Cunningham manufacture. AudioTron disappeared from advertisements by December 1922 and the name E. T. Cunningham Inc. appeared; later records place the company in Harrison, New Jersey. In 1931 it was described as a subsidiary of the Radio Corporation of America. The change from tube maker to a brand marketed within RCA's system is essential when dating and attributing surviving examples.

The Cunningham name remained visible on tubes and in technical literature after the change in production. The Cunningham Radiotron RC-12 manual, published in Harrison by RCA's receiving-tube division in 1934, shows the two names together. A Cunningham valve must therefore be interpreted through its type, marking and date: early AudioTrons belong to the Oakland phase, while later series reflect RCA supply and distribution. The survival of the brand does not erase the difference between these two industrial periods.