Exhibit J, one of seven breadboard exhibits using "gridless" tubes, used in the patent suit of RCA v. Heintz and Kaufman in 1936-37. Although the first gammatrons were built in 1928 and 1929, the exhibits for the trial were built in 1935 and 1936. RCA, which had been threatening to sue Heintz and Kaufman for years, finally sued H&K in federal court for infringement of RCA owned de Forest patents. H&K assembled a strong technical defense, including Stanford electrical engineering professor Frederick E. Terman, to attack the validity of the de Forest patents. Exact replicas were built from drawings by earlier inventors, and presented in depositions and pre-trial demonstrations by Ralph Heintz. When the trial opened, RCA's lawyers withdrew their complaint rather than risk losing the suit and possibly valuable patent authority.