ABSTRACT

It should be borne in mind that all current TV standards in use today are derived from the “black and white” TV standards started in the 1940s and 1950s, which have defined their framework.

The first attempts at electromechanical television began at the end of the 1920s, using the Nipkow disk for analysis and reproduction of the scene to be televised, with a definition of 30 lines and 12.5 images per second. This low definition resulted in a video bandwidth of less than 10kHz, allowing these pictures to be broadcast on an ordinary AM/MW or LW transmitter. The resolution soon improved to 60, 90, and 120 lines and then stabilized for a while on 180 lines (Germany, France) or 240 lines (England, the United States) around 1935. Scanning was progressive, which means that all lines of the pictures were scanned sequentially in one frame, as depicted in Figure 1.1 (numbered here for a 625-line system).