After Valdemar Poulsen invented magnetic recording in 1898, his associate Peder Oluf Pedersen patented the steel plate in 1901 as a "magnetizable body." The first devices had a magnetic plate with a diameter of 5 inches and a recording time of 45 seconds. The improved recorder from American Telegraphone Co. has a magnetic disk diameter of 12 inches. It was virtually impossible to sell the device due to its cost—$300 for 4 minutes of recording. A phonograph was available for $70.