During the 1920s and 1930s, many companies tried to develop a triode vaccum tube that would side-step de Forest and RCA, patents that were the backbone of the "Radio Trust." The Heintz and Kaufman Gammatrons were a rare and notable success.The Perham Collection includes many examples of both experimental and production gridless gammatron tubes, given to Douglas Perham by his friend Ralph M. Heintz. The Perham Collection may have the only example of the Type 155 Gammatron. With a plate dissipation of 150 watts, it was intended for the amateur market. It was rejected by Heintz as too small, and never went into production.