John Logie Baird may have been broadcasting television programmes regularly by 1929, but his work was based on earlier experiments.
Baird's apparatus was an improvement on Paul Nipkow's scanning disk. When he invented it in 1884, Nipkow was trying to improve and simplify G.R.Carey's work with photoelectric cells.
Carey, in turn, was only able to make his first crude television in 1875 because of John Jakob Berzelius' discovery of photoconductivity in 1817.
But then, that's what science is all about. You experiment to continue the work that other scientists started.