Original sentence: But Swinton noted that the "real difficulties lie in devising an efficient transmitter", and that it was possible that "no photoelectric phenomenon at present known will provide what is required".. Perhaps the first description of such a CRT imaging device appeared in a patent application filed by Edvard-Gustav Schoultz in France in August 1921, and published in 1922
Edited sentence: A description of such a CRT imaging device appeared in a patent application filed by Edvard-Gustav Schoultz in France in August 1921, and published in 1922, though a working device was not demonstrated until Farnsworth did so some years later.But Swinton noted that the "real difficulties lie in devising an efficient transmitter", and that it was possible that "no photoelectric phenomenon at present known will provide what is required"