 Complete the following phrase:  As a 23-year-old German university student, Paul Julius Gottlieb Nipkow, proposed and patented the Nipkow disk in 1884. This was a spinning disk with a spiral pattern of holes in it, so each hole scanned a line of the image. Although he never built a working model of the system, variations of Nipkows spinning-disk image rasterizer became exceedingly common. Constantin Perskyi had coined the word television in a paper read to the International Electricity Congress at the 