Before totally electronic TV cameras and receivers were built, the electromechanical "scanning disc" produced the first video images. As far back as 1884, German inventor Paul Nipkow designed such a system. Using a rotating disk with a spiral pattern of holes, light from the subject came through the holes and reached a selenium photocell, thereby breaking up the image into pixels. Each rotation produced one TV frame. Photosensors detected the brightness of each pixel similar to today's cameras, and the light was modulated into an electronic signal.
At the receiving end, the signal was synchronized with a rotating disk that had the same spiral pattern. The signal modulated a neon lamp that beamed through the disk's holes to a magnifying lens that the viewer looked into.
The Scanning Disc TV - A Modern Miracle
In the 1920s, scanning disc systems were being developed at Bell Labs and General Electric, as well as by John Logie Baird in London and Charles Jenkins in Baltimore.
In 1928, using his "Radiovision" system, Jenkins is credited with starting the first TV station in the U.S. in Wheaton, Maryland. Using proprietary systems with receivers mostly sold in kit form, mechanical disc TV was transmitted from approximately 20 stations. The broadcasting was limited, and the audience was even more limited. Images were blurry, and the tuning knob had to be constantly adjusted; nevertheless, these systems were considered modern miracles.
By 1935, it became apparent that mechanical systems would never become commercial. Synchronizing the discs and modulating light sources at the higher speeds necessary to make an image acceptable were impossible to achieve.
Scanning Disc TV
Get Noctovised (1927)
In the mid-1920s, Scottish inventor John Logie Baird and American inventor Charles Jenkins demonstrated the first scanning disc systems. The top picture shows one of Baird's scanning discs, and the bottom his receiver. These systems had a resolution of 30 lines (see VTR
). (Images courtesy of TVhistory.TV)
Another Baird invention was the Noctovisor, a similar system that used infrared light with subjects sitting in the dark. Looking like early science fiction, the seated gentleman in this image was "Noctovised" to London. (Image courtesy of www.TVhistory.TV)
All Electronic - Zworykin and Farnsworth
Throughout the 1920s, RCA's Vladimir Zworykin was busy developing the Iconoscope camera tube that would become the foundation for the all-electronic TV. Zworykin's work was based on a CRT receiver invented by his instructor in 1907 at St. Petersburg Institute of Technology in Russia.
At the same time, Philo Farnsworth was also developing an electronic TV, which he patented and demonstrated in 1927. Farnsworth's patent was approved in 1930, but Zworykin's 1923 patent would not be approved until 1938 because so many revisions were made. For a brief time, Farnsworth and Zworykin were racing to perfect their technologies with just a river between them: Farnsworth in alliance with Philco in Philadelphia and Zworykin at RCA in Camden, New Jersey, directly across the Delaware River.
RCA Paid Farnsworth
Although Sarnoff wanted RCA to control TV as it had radio, it was proven that Zworykin's system infringed on some of Farnsworth's patents. RCA reluctantly paid Farnsworth royalties until the patents ran out, but years of delay tactics had taken their toll. By the late 1940s, the last of Farnsworth's company was sold to International Telephone and Telegraph (ITT), and Farnsworth went to work for ITT as a scientist, devoting much of his remaining life to nuclear fusion.
RCA Was Convincing
In the 1930s, Radio Corporation of America was a powerful electronics company. Its PR machine was huge, and nobody would forget its spectacular demonstration of TV at the 1939 World's Fair. Citing Zworykin's 1923 patent application and coating everything with RCA-colored glasses, it succeeded in making everyone believe that RCA, Sarnoff and Zworykin were the sole creators of electronic television. In 1939, NBC began to broadcast TV using the RCA system, and two years later, NTSC was approved. In 1941, the U.S. finally had a national, electronic TV standard, which lasted until 2009 (see DTV
). See NTSC
All Electronic Live TV (1939)
This RCA video camera used the all-electronic Iconoscope picture tube, but had no viewfinder. That came later. Recording video on magnetic tape would not come until 1956. (Image courtesy of the Early Television Museum, www.earlytelevision.org)
Imagine Shopping by TV (1945)
Co-sponsored by RCA Victor, the Gimbel Brothers department store in Philadelphia was a trailblazer - showing merchandise on TV. Seven out of ten people watching had never seen television before. (Image courtesy of the Early Television Museum, www.earlytelevision.org)
Early Color TV (1954)
The first color broadcast in the U.S. was the 1954 New Year's Day Tournament of Roses Parade in Pasadena, California. Color TV had just emerged and TV sets like this CBS floor model were very pricey compared to black and white. As more TV stations transmitted in color, color TV sales took off in the 1960s. (Image courtesy of the Early Television Museum, www.earlytelevision.org)