A number of such mechanical television systems were being used experimentally in the 1920s. The best-known was John Logie Baird's, which was actually used for regular public broadcasting in Britain for several years. Indeed, Baird's system was demonstrated to members of the Royal Institution in London in 1926 in what is generally recognized as the first demonstration of a true, working television system. In spite of these early successes, all mechanical television systems shared a number of serious problems. Being mechanically driven, perfect synchronization of the sending and receiving discs was not easy to ensure, and irregularities could result in major image distortion. Another problem was that the image was scanned within a small, roughly rectangular area of the disk's surface, so that larger, higher-resolution displays required increasingly unwieldy disks and smaller holes that produced increasingly dim images. Rotating drums bearing small mirrors set at progressively greater angles proved more practical than Nipkow discs for high-resolution mechanical scanning, allowing images of 240 lines and more to be produced, but such delicate, high-precision optical components were not commercially practical for home receivers.