1937 Radio Engineering
About Scanning Lines
The clarity of the television picture is directly dependent on the number of scanning lines. In the earliest of TV days (1920s, early 30s), the number of scanning lines for mechanical television was mostly 30, 48 or 60. Over time, the scanning systems were improved. When electronic scanning was developed, the number of lines increased to 120, 180, 240, 343/345, (405 England), 441, and finally today's 525 (625 in England). USA HDTV is 1080 lines.
There were even other variations (not shown in the previous list) in line counts, between different manufacturers, different countries, etc., in the early experimental days of electronic television. (If someone has a complete list of the various line standards and the dates they were used, I would like to post a copy.)
A good illustration of the difference in the quality of the TV picture, with increasing line counts, is shown here:
The February issue of Radio Engineering announced the FIRST PUBLIC DEMONSTRATION of television using the new 441-line electronic scanning system. This demonstration was given by Philco Radio & Television Corp., at Philadelphia, on February 11, 1937. A scan of that article is below: