. Discovery. Science. KMMKEIIT â UCUCT Via. 2. Fig. 3. DIAGRAJKtVTIC ARRANGEMEXT OF OPTOPHONE. be obtained. These are, of course, well-known facts. It is the role played by the selenium which is the novel feature. In the optophone a selenium bridge is exposed to successions of sets of light pulsations, which vary ac- cording to the forms of letters as these are passed over in traversing a line of printed type, each letter being indicated in the telephone by a characteristic motif comprising successions of single notes and chords. And the letters of this sound alphabet can be readily learned. T
. Discovery. Science. KMMKEIIT â UCUCT Via. 2. Fig. 3. DIAGRAJKtVTIC ARRANGEMEXT OF OPTOPHONE. be obtained. These are, of course, well-known facts. It is the role played by the selenium which is the novel feature. In the optophone a selenium bridge is exposed to successions of sets of light pulsations, which vary ac- cording to the forms of letters as these are passed over in traversing a line of printed type, each letter being indicated in the telephone by a characteristic motif comprising successions of single notes and chords. And the letters of this sound alphabet can be readily learned. The optophone is quite small, not much bigger than a portable type\vriter, and externally (Fig. i) there is not much to be seen, just a glass table on which the book or other printed matter rests face downwards. To understand the mechanism of the machine, the reader must glance at the diagrammatic views of the mysteries hidden away under this table. Each letter is illumined in turn by the light which is thrown up from beneath, and which is made to travel along the lines of print by a specially designed variable speed governor. The source of light is a small straight electric filament lamp (Figs. 2 and 3), the rays of which are made to pass through a diaphragm on to a per- forated disc (Fig. 4), which is caused to rotate rapidly by means of a small magneto-electric motor driven from secondary cells. The light which passes through this disc is directed by suitable lenses on to the printed page, and traverses an aperture in the selenium tablet which is placed directly under the glass table. As this tablet travels along with the rest of the optical apparatus to which it is attached, it catches the light diffusely reflected from the white paper surrounding each letter in turn. This the makers call the " main selenium bridge," to distinguish it from the " balancer ; the object of which will shortly be explained. Both these bridges are shown in their various
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