An early mechanical-scan television camera made by Jenkins Co., Passaic, New Jersey, used in experimental television broadcasts in the 1930s. This used a large spinning disk called a Nipkow disk "(visible in housing at front of camera)" pierced by a spiral pattern of holes, rotating behind the lens. Each hole, passing across the image, produced a scan line of video. A phototube in back of the disk produced a video signal which varied with the brightness of the image at each point. Dozens or experimental television stations during the 1920s and 30s broadcast with these mechanical-scan television systems.