Mechanical television or mechanical scan television is a television system that relies on a mechanical scanning device, such as a rotating disk with holes in it or a rotating mirror, to scan the scene and generate the video signal, and a similar mechanical device at the receiver to display the picture. This contrasts with modern television technology, which uses electronic scanning methods, for example electron beams in cathode ray tube (CRT) televisions, and LCD displays, to create and display the picture. Mechanical-scanning methods were used in the earliest television systems in 1920s and 1930s. By late 1920s many radio stations were broadcasting experimental television programs using mechanical systems. However the technology never produced high enough quality images to become popular with the public. Mechanical-scan systems were largely superseded by electronic-scan technology in the late 1930s, which was used in the first commercially successful television broadcasts which began in the late 1940s.A mechanical television receiver is also called a televisor in some countries.