In view of the multipath distortion experienced on the long distance circuits, time modulation has proven the most succesfull. The so-called CFVD arrangement, suggested by Callahan, Shore and Withacker, has been adopted by the commercial organisations operating the international radio facsimile circuits.
Acceptable copy can be transmitted by this keying method if slow handling and a low order of keying speed is employed. Increasing knowledge of the radio propagation medium should provide the basis for increased handling speed with acceptable quality. The work of Dr. Hudec in Germany was a step in this direction.
The Following documents are representative at the end of thirties of the time modulation applications.
Delany (U. S. Patent 316,754, P. B. Delany).
Amstutz (U. S. Patent 1,019,403, N. S. Amstutz).
Bartholomew (U. S. Patent 1,653,425, H. G. Bartholomew).
Walker (Wireless World, Vol. 30, pp.
Engineering (Engineering, Vol. 137, No. 3553, pp. 203-204, February 16th, 1934).
Television (Television Vol. 8, No. 94, pp. 702-752, December, 1935, E. Belin).
Callahan, Shore and Withacker
Alexanderson and Ranger (U. S. Patent 1,787,851, E. F. W. Alexanderson and R. H. Ranger).
Rea (U.S. Patent 2,086,679 W. T. Rea)
Watson (U.S. Patent 1,579,263, E. F. Watson)
Watson & Weaver (U.S. Patent1,602,469. E. F. Watson and Allan Weaver)
(U.S. Patent1,664,652. E. F. Watson and Allan Weaver)
Bartholomew & Deedes ( U. S. Patent 1,910,586, H. G. Bartholomew and M. L. Deedes)
Alexanderson (U. S. Patent 1,839,456, E. F. W. Alexanderson.)
Hudec (Elecktrische Nachrichten Technick, December, 1937, Fernsprech und Funk Technick, January, 1938, E. N. T., No. 10, October, 1937, and Telegraphen Fernsprech und Funk Technick, No. 7, 1937, E. Hudec.)
Culver (U. S. Patent 1,898,080, C. A. Culver.)
Fulton (U. S. Patent 1,902,552. O. Fulton)
Schroter & Runge (U. S. Patent 1,914,898, F. Schroter and W. Runge)
Gardner (U. S. Patent 1,950,171, P. C. Gardner)
McFarlane (U. S. Patent 2,002,208, M. D. McFarlane)
Bailey (U. S. Patent 2,047,817, A. Bailey)
Finch (U. S. Patent 2,066,261 and U. S. Patent 2,066,262 W. G. H. Finch)
Herrmann (U. S. Patent 2,095,701 J. Herrmann)
Philpott (U. S. Patent 2,103,793, L. R. Philpott)
Eastmann & Hatch (Marconi Rev., No. 47, pp. 1-12, March-April, 1934, J. W. Eastman and J. F. Hatch)
Noizeux (Revista Telegrafica, Vol. 25, pp. 728-730, September, 1936, P. J. Noizeux)
Kobayashi (Elec. Communication, Vol. 16, No. 2, pp. 144-152, October, 1937, Masatsugu Kobayashi)
Wright & Smith (U. S. Patent 1,995,138, G. M. Wright and S. B. Smith)
- (C) Marius Rensen