In the United Kingdom, Rank Precision Industries was experimenting with the flying-spot scanner (FSS), which inverted the cathode ray tube (CRT) concept of scanning using a television screen. The CRT emits a pixel-sized electron beam which is converted to a photon beam through the phosphors coating the envelope. This dot of light is then focused by a lens onto the film's emulsion, and finally collected by a pickup device. In 1950 the first Rank flying spot monochrome telecine was installed at the BBC's Lime Grove Studios. The advantage of the FSS is that colour analysis is done after scanning, so there can be no registration errors as can be produced by vidicon tubes where scanning is done after colour separation—it also allows simpler dichroics to be used.