A few months after arriving in California, Farnsworth was prepared to show his models and drawings to a patent attorney who was nationally recognized as an authority on electrophysics. Everson and Gorrell agreed that Farnsworth should apply for patents for his designs, a decision that proved crucial in later disputes with RCA. Most television systems in use at the time used image scanning devices ("rasterizers") employing rotating "Nipkow disks" comprising a spinning disk with holes arranged in spiral patterns such that they swept across an image in a succession of short arcs while focusing the light they captured on photosensitive elements, thus producing a varying electrical signal corresponding to the variations in light intensity. Farnsworth recognized the limitations of the mechanical systems, and that an all-electronic scanning system could produce a superior image for transmission to a receiving device.