 Meanwhile, innovations continued on another significant front.In 1900, as part of the research he was conducting on the photophone, the German physicist Ernst Ruhmer recorded the fluctuations of the transmitting arc-light as varying shades of light and dark bands onto a continuous roll of photographic film.He then determined that he could reverse the process and reproduce the recorded sound from this photographic strip by shining a bright light through the running filmstrip, with the resulting varying light illuminating a selenium cell.