In 1913, Dr. Edmund Fournier d'Albe of University of Birmingham invented the optophone, which used selenium photosensors to detect black print and convert it into an audible output. A blind reader could hold a book up to the device and hold an apparatus to the area she wanted to read. The optophone played a set group of notes: g c' d' e' g' b' c" e". Each note corresponded with a position on the optophone's reading area, and that note was silenced if black ink was sensed. Thus, the missing notes indicated the positions where black ink was on the page and could be used to read.