Television as a technology began with experiments in the late 19th century. The earliest cathode ray tube (CRT), fundamental to modern TV, was invented by Karl Ferdinand Braun in 1897. The word "television" was coined in 1900. The first public demonstration of a television system occurred on March 25, 1925, by Scottish inventor John Logie Baird, who used a mechanical system. Electronic television, which uses electronic signals and cathode ray tubes, was first successfully demonstrated in San Francisco by Philo Taylor Farnsworth on September 7, 1927. Farnsworth transmitted the first electronic TV image, a simple straight line, and later improved the system to transmit live human images. TV started becoming more widespread commercially around the late 1930s, with RCA broadcasting at the 1939 New York World’s Fair. Color TV systems began development in the 1940s and 1950s, entering commercial broadcasting by the early 1950s. In summary, TVs were invented in stages: mechanical TV in the mid-1920s, electronic television in 1927, with commercial and color TV developing in the subsequent decades.