General Electric's Porta-Color was the first "portable" color television introduced in the United States. The Porta-Color set introduced a new variation of the shadow mask display tube invented by RCA. It had the electron guns arranged in an in-line configuration, rather than RCA's delta arrangement. The GE tube otherwise used the same kind of round dot phosphors as RCA, The main benefit of the in-line gun arrangement is that it simplified the convergence process, thus making true portability possible. There were many variations of this set produced from its introduction in 1966 until 1978, all using GE's Compactron vacuum tubes (valves).