Early film reel and sound coding. Four film reel frames from a DeForest Phonofilm 'The Bride' (featuring British comedian George Robey, 1869-1954). This film reel was used for the first 'tele-talkie' demonstration in August 1929 by the Scottish engineer and inventor John Logie Baird (1888-1946). The DeForest Phonofilm system recorded sound directly onto the film as parallel lines of varying density resembling a barcode, seen here on the right. A narrow slit of light passed through the variable-density track onto a photo electric cell, and this was then transmitted and converted back into sound. At this point, Baird was still developing his mechanical televion model, here using a Mechau continuous-motion projector, while the images were obtained by scanning with a 30-hole disc.