Well, it all goes back to a little invention by Paul Nipkow in 1884
consisting of a disk with holes spiraling into its center. I know it's
hard to believe, but this little disk shaped the development of television.
Engineers like John Logie Baird and Charles Francis Jenkins, among others,
used Nipkow's disk to create the first systems for scanning, transmitting,
and receiving images in the 1920's. These guys created entire television
systems based on mechanical image scanning and receiving. No Cathode
Ray Tubes (CRTs) here.
Electronic television systems lagged behind mechanical systems for
several years, mostly because mechanical television was cheaper to build
and it didn't use delicate parts. Not only that, but it was really hard
to get financial backing to develop electronic TV when mechanical TV
worked so much better at the time. With a cheaper system that already
worked, few people saw the need to change. Then Vladimir Kosmo Zworykin
and Philo T. Farnsworth made some critical breakthroughs, and electronic
television began to catch up.
Vladimir Zworykin found financial backing from David Sarnoff, Senior
Vice President of RCA. Sarnoff was watching mechanical television development
and predicted that electronic TV would eventually be more commercially
viable. Later, when Philo Farnsworth found some investors to back his
ideas, he and Zworykin competed to get their electronic televisions
to the public first.