Editing Shadow mask (section)

===Numerous attempts===
Through the 1940s and early 1950s a wide variety of efforts were made to address the color problem. A number of major companies continued to work with separate color "channels" with various ways to re-combine the image. RCA was included in this group; on 5 February 1940 they demonstrated a system using three conventional tubes combined to form a single image on a plate of glass, but the image was too dim to be useful.<ref name=dot/>

[[John Logie Baird]], who made the first public color television broadcast using a semi-mechanical system on 4 February 1938, was already making progress on an all-electronic version. His design, the [[Telechrome]], used two electron guns aimed at either side of a phosphor covered plate in the center of the tube. Development had not progressed far when Baird died in 1946.<ref>[http://www.bairdtelevision.com/colour.html "The World's First High Definition Colour Television System"] {{Webarchive|url=https://web.archive.org/web/20170511162325/http://www.bairdtelevision.com/colour.html |date=11 May 2017 }}, Baird Television.</ref> A similar project was the [[Geer tube]], which used a similar arrangement of guns aimed at the back of a single plate covered with small three-sided phosphor covered pyramids.<ref>[https://web.archive.org/web/20110131074757/http://www.time.com/time/magazine/article/0,9171,858780,00.html "Teacher's Tube"], ''Time'', 20 March 1950.</ref>

However, all of these projects had problems with colors bleeding from one phosphor to another. In spite of their best efforts, the wide electron beams simply could not focus tightly enough to hit the individual dots, at least over the entirety of the screen. Moreover, most of these devices were unwieldy; the arrangement of the electron guns around the outside of the screen resulted in a very large display with considerable "dead space".